Description of image formats. Graphic formats. What are image formats

There are several extensions used for each file type. This is because they are processed by different programs that encode them based on content, compression, and other features. Graphic file formats can be divided into raster and vector. If you are going to get acquainted with computer graphics, then you need to know everything about them. File formats play an important role in preparing print layouts, designing, placing images on Web pages, and many other types of work.

Raster type of graphic images

Raster graphics are based on pixels that are organized into rows and columns. They represent surface rendering elements. They are independently assigned color, transparency, and other properties. Image quality and pixel count are related: the more pixels used, the better the final image will look.

Raster graphics have several advantages:

wide scope of application (with their help you can transfer objects of the real world using photos);
graphic information is easy to process;
printing can be done on any equipment; standard printers easily construct an image from pixels;
Most raster formats are accepted by any program for processing and displaying images on a monitor.

But when working with them, you need to take into account a number of disadvantages:

The file size can be very large, which will make it difficult to transfer (this most often happens with uncompressed images);
editing a raster image is more difficult, since the pixels become an integral part of the overall picture, and are not perceived as independent units;
formatting and transformation can distort the image.

Nevertheless, we come across raster images most often. Any camera creates images in this format.

In what formats are raster files saved?

Popular raster graphics file formats can be found on every computer. Most of them you have seen on your device. Raster formats include:

Bit Map (BMP, extension - bmp) is a file with the most wasteful encoding, one of the standard graphic formats used in the very first versions of Windows. Initially, only 256 colors were available to users, and each pixel was equal to one byte. Now you can use BMP to store full-color images. The main program for working with it is Paint, but you can open it through Photoshop and other editors.
Tagged Image File Format (TIFF, tif extension) is a universal cross-platform format used to transfer images between users. It is most often used in publishing and in the preparation of topographic maps, since it can be used to obtain a clear image on a printed version of the picture. Installed by default in utilities that work with scanners and faxes. Not suitable for websites as images are heavy. It is best to work with it using the FastStone program - it allows you to view the contents of the file, process and convert it.
Graphic Interchamge Format (GIF, extension - gif) is a format that supports animation without losing information during compression. Widely used on the Internet, despite the limited number of colors. The appearance of the image does not change when used to view different browsers and platforms. The following programs work with the format: Viewer, Paint, Adobe Photoshop, Visio.
PhotoShop Document (PSD, extension - psd) is an internal raster graphics format used for the Adobe Photoshop software package. Its peculiarity is that the image retains all layers and can therefore be easily edited.
Portable Network Graphics (PNG, extension - png) is a free format in which the image is compressed without loss, which allows it to be used in various areas of computer graphics. Work with this program format : Viewer, Paint, Photoshop, Visio, Corel PaintShop Pro.
Joint Photographic Expert Group (JPEG, extension – jpg) – stores images by compressing them. This format is considered the standard for full-color images. It is used to record photographs taken from cameras and is used in computer graphics. It features a smooth change in brightness and color in the work area. During compression, data that does not have a significant effect on the final image is excluded from the file. The entire drawing is divided into rectangular areas, sometimes resulting in a blurry image. Image processing can be carried out using the following utilities: FastStone Viewer, Paint, Adobe Photoshop, Visio.
Joint Photographic Expert Group 2000 (JPEG 2000, extension - jp 2) - allows you to get sharper images when compressed, while the file weight becomes smaller. It is processed by the same programs as its prototype. It is not very common because not all browsers support it.
Windows I con (ICO, extension - ico) - used to create small format images and icons. These images mark sites in the address bar or in the “Favorites” bar of browsers. The following programs are used to work with this format: Inkscape, Newera Iconcool Editor, Sibcode Sib Icon Editor.
RAW (extensions: ari, dpx, arw, srf, sr2, bay, crw, cr2, dng, dcr, kdc, erf, 3fr, mef, mrw, nef, nrw, orf, ptx, pef, raf, raw, rwl, dng, rw2, r3d, srw, x3f) is a form called digital negative. Used when saving images with professional cameras. There is no general standard for expanding this format, so each equipment manufacturer creates its own version and software that can work with it and convert it into other generally accepted options.

The variety of graphic file formats can confuse even a professional, so many programs are able to work immediately with files with different extensions. One of them is Photoshop, which is the most popular among users.

Vector type of graphic images

Advanced users know another type of images built on the basis of regular structures. In a primitive understanding, vector graphic file formats are a diagram that is made up of the simplest shapes: triangles, segments, straight lines, rectangles and others. The advantages of vector files are:

small file size if the drawing is made up of graphic primitives;
scaling occurs without loss of quality;
When outputting vector images, the maximum resolution of the printer or other device is used.

Such images have a number of significant disadvantages:

You cannot create realistic images using vector graphics;
it is impossible to automate the input of graphic information due to the heterogeneity of the elements;
Each program has its own format in which it saves images; the files depend on the utilities.

A large number of programs used to work with vector graphics were created because each of them performs its own tasks. Unlike raster images, vector images are used in design, architecture and other areas. Often, working with drawings requires high precision and a wealth of special knowledge.

Vector image formats

The most common vector graphic file formats are:

CDR (cdr extension) is an internal format of the CorelDRAW software package. Allows you to save images created in this program and text. This software package can also use other special formats: CDT, CDX, CGM, CLK, CMX, CPX, CSL, DES, DRW, DSF. Some of these formats support the combined use of raster and vector graphics. They are used for various CorelDRAW applications and can be used to create different images, templates and video clips.
AI (ai extension) is a format used in Adobe Illustrator. When working with this file, it is worth remembering that a file created on a recent version of the software cannot be opened on an outdated version of the utility. This format is loved for its high quality graphics, but its drawback is that a number of effects are lost during its conversion, for example, gradient fill.
EPS (eps extension) is a format supported by many vector graphics programs. It has several versions, which are indicated by numerical values, but many programs do not support EPS above 7. Thanks to this format, conversion is resorted to in extreme cases, because it is much easier to save the file in it than to restore lost properties later.
DXF (dxf extension) is a format with which AvtoCAD design applications and its analogues work. The files support many features not found in other vector-based options, such as saving 3D objects.
WMF (wmf extension) - used to work with applications based on Windows OS. This is a universal tool used to display images on computer screens and printers.
SWG, SVGZ (extensions - swg, svgz, differing in the percentage of image compression) - a format used to design web pages. All popular browsers support it. It cannot be used to store complex designs, so its scope of use is very limited.
TGA (tga extension) is a popular format used in motion graphics and video editing. Information is stored at a depth of 32 bits per point. This is a universal file option that can also be used to store raster images.
FLA, FH (extensions fla , fh ) – used to store the original versions of Flash images. Open only on Adobe software. In particular, they use the Flash program and the vector editor FreeHand.

The popular format for PDF documents can also be classified as vector. Initially, it was not planned that it would be used to transfer images, but now more and more often users save information mixed in content - text and graphics - in it. In this case, the illustrations in this document can be either vector or raster. The text part contains a large number of fonts. This format was also presented to the world by Adobe.

How to change image formats?

The need to convert one file format to another most often arises for the following reasons:

incompatibility of the software with the current extension;
there was a need to reduce the size;
you need to process the file in another program, and not in the one in which it was created;
to meet the requirements of the file hosting environment (for example, when placing graphics on a web page).

Conversion of graphic file formats is carried out using utilities. For example, in Adobe Photoshop you can save files with an extension other than just for internal use. Using the “Save for Web” command, about a dozen popular raster formats will be available to you. Other programs for working with images have similar capabilities; for example, in CorelDRAW you can not only change the format of the created graphics, but also transform the vector version into a raster one.

You can also use separate applications called converters for transformation. Most have a wide range of available formats, but it's best to use options that only work with a few extensions. Examples of the best graphics conversion utilities:

Flash-SWF to AVI/GIF/MP3 Converter;
FormatFactory;
VeryDOC EMF to EPS ;
Image Converter;
DWG to BMP;
Aunsoft SWF Converter;
Uniconvertor;
GraphicsConverterPro ;
Converter 3Plus;
Solid Converter DWG;
Photo to PDF;
Raster to Vector SDK.

Most programs work with vector files, since they are most common and not only professional designers and planners work with them.

Another opportunity to convert and work with files is provided by plugins that complement standard graphic editors. One of them is Irfan View. It allows your software to work not only with basic extensions, but also with more than 20 other formats.

Now you know what the graphic file formats are. This article lists basic information about them. We recommend saving it and sharing your new knowledge with friends. You can also ask questions in the comments and tell them about your experience working with graphics.

Which store any type of persistent graphical data (“images”) intended for subsequent visualization. The ways of organizing these files are called graphic formats. Once written to a file, the image ceases to be an image itself - it turns into digital data. The format of this data may change as a result of file conversion operations. Depending on the nature of the graphics supported, file formats are classified into one of the following types: raster format, vector format, metafile format. The most common graphic formats:

AI (Adobe Illustrator, Adobe AI) - a metafile format developed by Adobe for Macintosh, Microsoft Windows, NeXT; used for recording and storing various types of images, including drawings, drawings and decorative inscriptions.

PSD (Photoshop Document, Adobe Photoshop, Adobe PSD) is a raster format included in the Adobe Photoshop graphic editor; used by publishing systems on PC and Macintosh platforms. PSD allows you to record with or without compression (RLE) an image with many layers, masks, additional channels, contours and other graphic elements.

ART is a format developed by Gonson-Grace, used for storing photographs and drawings.

AutoCAD DXF (Drawing Interchange Format) and AutoCAD DXB (Drawing Interchange Binary) are two versions of the same format (without data compression), developed and supported by Autodesk for the AutoCAD CAD program running on the MS-DOS platform. DXB is a simplified (binary) version of the seven-bit DXF. In addition to AutoCAD, the format is supported by many CAD programs, CorelDRAW and others, in particular, for exchanging data of different types: vector-oriented data, texts, three-dimensional drawings. However, a number of programs that claim to support DXF import implement only some of its capabilities. DXF changes with each version of AutoCAD. DXF and DXB file names use the extensions *.dxf, *.dxb, *.sld, *.adi.

BDF (Bitmap Distribution Format) is a raster format developed by the X Consortium for exchanging bitmap font data between X Window and other systems. There is no compression, the maximum image size is not limited, the color is monochrome. Each BDF file stores data for only one typeface (a group of fonts united by a single name).

BMP is a raster format developed by Microsoft for Windows OS; supported by all graphic editors working under its control, capable of storing both indexed (up to 256 colors) and RGB color (16.7 million shades). Most BMP files are stored in uncompressed form.

CDR (CorelDRAW Document) is a vector format initially known for its low stability and poor file compatibility. Many PC programs (FreeHand, Illustrator, PageMaker) can import CDR files. Starting from the seventh version, CorelDRAW in CDR files applies compression separately for vector and raster graphics; fonts can be embedded.

CGM (Computer Graphics Metafile) is a standard (ANSI and ISO) and metafile format for displaying vector images on the Web, adopted at the end of 1998 by the 3WC (WWW Consortium). The format is focused on supporting a variety of graphic images, including artistic graphics, technical illustrations, cartography, and computer publishing systems. Although CGM contains many graphics primitives and attributes, it is less complex than PostScript, allows for the creation of more compact files, and supports the exchange of complex, high-quality artistic images. The format uses different types of compression (RLE, CCITT Group 3 and Group 4); the color palette is not limited. One CGM file can contain multiple images.

CPT is a raster format of the Corel PHOTO-PAINT program, provides storage of full-color images and vector objects.

DPX (Digital Picture Exchange Format; also known as SMPTE Digital Picture Exchange Format) is a raster format designed to store one film frame or video data stream; developed by Kodak Cineon, adopted by ANSI and the US Society of Motion Picture and Television Engineers (SMPTE) with minor modifications as a standard. The format is supported by Kodak programs.

DWG is a vector format of the AutoCAD program from Autodesk, designed for storing drawings.

EMF (Enchanced Metafile) is a metafile format developed by Microsoft for storing images as a sequence of commands leading to the reproduction of images. In November 2005, the vulnerability of EMF and WMF formats from “buffer overflow attacks” was discovered, and at the end of December, a family of Internet worms appeared. The infection occurred when users visited a number of sites that used the WMF vulnerability to download Trojan programs to a remote machine. Soon, stand-alone versions of viruses appeared, spreading in the form of email worms in attached image files. Microsoft responded to this threat by issuing Security Advisory 912840, as well as (January 11, 2005) patching Windows XP, Windows 2000 (Service Pack 4), and Windows Server 2003.

3DS (3D Studio, ASC) - a format developed by Autodesk, a three-dimensional modeling tool (“scene description”); also used as an interchange format. The format ensures optimal distribution of resources on the PC platform, supports all colors without restrictions, and has no compression. Many 3D modeling programs read and write files in this format. Strictly speaking, 3DS is two formats that are used as exchange formats - binary with the *.3ds extension and text with the *.asc extension.

EPS (Encapsulated PostScript, EPSF) is a simplified version of the PostScript format (PDL), developed by Adobe as a vector format, and later its raster version appeared - Photoshop EPS. The EPS format cannot contain more than one page in a single file and does not preserve a number of printer settings. Like PostScript print files, the EPS format records the final work, although programs such as Adobe Illustrator, Photoshop and Macromedia FreeHand can use it as a production tool.

FH8 (FreeHand Document) is the eighth version of the FH format, intended only for Macintosh PCs. FreeHand itself, Illustrator 7 and a limited number of programs from Macromedia can work with it. Starting from the seventh version, the FH format has full cross-platform compatibility, however, some FreeHand effects are not compatible with PostScript.

FIF (Fractal Image Format) is a format developed by Iterated Systems, used for storing photographs on the Internet, and supports its own FIF compression system.

FITS (Flexible Image Transport System, FTI) is a raster format and image storage standard used by many organizations (including scientific organizations, government agencies) for storing astronomical (obtained by orbital vehicles) and terrestrial images (in particular, radio astronomy data and digitized photographic images) . The format is widely used to exchange data between different hardware platforms and software applications that do not support a common file format. FITS is considered a fairly simple, uncompressed format with an “unlimited number” of shades of gray. It can store many types of data, including raster, ASCII text, multidimensional matrices, binary tables.

GIF (Graphics Interchange Format) is a standard raster format for presenting images on the WWW; was developed in 1987 by CompuServe, overshadowing the older PCX and MacPaint formats. Main advantages: the ability to use on many platforms and the availability of an efficient 12-bit LZW compression algorithm with free (until 1994) implementations. The format allows you to well compress files in which there are a lot of uniform fills (logos, inscriptions, diagrams), record an image “through the line” (Interlaced mode), thanks to which, having only part of the file, you can see the entire image, but with a lower resolution (GIF supports resolution up to 66536x65536).

IFF (Interchange File Format), ILM, ILBM, LBM (InterLeaved BitMap), Amiga Paint - a family of raster formats developed and supported for the MS-DOS, UNIX, Amiga platforms by Electronics Arts and Commodore-Amiga. A distinctive feature of IFF is its versatility: it can be used not only to support graphics, but also sound on all platforms except Amiga. IFF was previously known as the 24-bit format for MS-DOS, but it began to be replaced by the TIFF and TGA formats, and then by the JFIF format. Some characteristics of the IFF format: maximum image size 64 K by 64 K pixels; used in uncompressed and RLE compression versions, supports colors from 1- to 24-bit; “Major in Minor” number format, has a specification on CD; when used with MS-DOS and UNIX, file names may have *.iff and *.lbm extensions.

JFIF (JPEG File Interchange Format), JFI, JPG, JPEG - a raster format from C-Cube Microsystems, has become most widespread, so most “JPEG” images would be more correctly called “JFIF”. Using JFIF, it is recommended to save only the final version of the work, since each intermediate save leads to data loss and distortion of the original image.

PCX (PC Paintbrush File Format) is one of the most common raster formats; designed for storing illustrations in desktop publishing systems. The format was developed by Zsoft for the Paintbrush program, and after concluding an OEM agreement with Microsoft Corporation, it began to be used in various systems that work with graphics. Main characteristics: maximum image size 64 K by 64 K; 24-bit color support; uses RLE compression (can work without compression); supports work with CD-ROM. The PCX format versions are DCX and PCC, whose file names have the appropriate extension.

PDF (Portable Document Format) is a metafile format proposed by Adobe for graphic files (vector and raster) containing illustrations and text with a large set of fonts and hypertext links for the purpose of transmitting them over the network in compressed form.

PDS (Planetary Data System Format) is a NASA standard format for storing data collected by spacecraft and ground-based observations about the Sun, Moon and planets; is also used by other organizations to store similar data. The basis of the format is the object description language - ODL (Object Description Language). The maximum image size and colors in PDS format are unlimited; supported on all platforms.

PGML (Precision Graphics Mark-up Language) is a vector format that describes graphics in terms of mathematical formulas rather than raster pixels, which saves disk space and allows image scaling without loss of resolution and other quality indicators. The format was submitted to the W3C (WWW Consortium) for consideration as a network standard by Adobe Systems, IBM, Netscape, Sun Macromedia; used on the Internet.

Photo-CD (PCD, Kodak Photo CD) is a raster format developed by Eastman Kodak and designed for storing and playing full-color images (usually photographs) recorded at various resolutions on CDs. The format is supported by Photo CD ACCess, Photoshop, Shoebjx. The Photo CD format supports 24-bit colors, has its own compression system, a maximum image size of 2048x3072 pixels, allows you to store only one image per file, uses RLE and JPEG compression systems (in the DCT version). Kodak does not disclose further details.

PIC (Pictor PC Paint, PC Paint) - a raster format developed by Paul Mace for drawing programs on the MS-DOS platform, is a hardware-dependent format created taking into account the requirements of the IBM family of graphics adapters (CGA, EGA, VGA). The PIC format is similar to the PCX format; the file names use the *.pic and *.clp extensions.

PICT (Macintosh QuickDraw Picture Format) is a standard for the Macintosh PC clipboard, supporting both raster and vector graphics. On a Macintosh PC, PICT works with all programs. On a PC it can be read by a number of programs, but working with it is rarely easy. PICT file names have the extension *.pic or *.pct.

PNG (Portable Network Graphics) is a raster format approved as a standard by the W3C (WWW Consortium) and intended to replace GIF. The format provides indexing of up to 256 colors, support for 24- and 48-bit color representation (True Color) and the implementation of a transparency channel (the so-called alpha channel). The dynamic lossless PNG image compression algorithm is 10-30% more efficient than a similar type of compression implemented in the GIF format.

PS (PostScript) - the format of the PostScript page description language (also known as the laser printer control language) was developed in 1984 by Adobe. The format is used for printing and storing fonts, as well as for exchanging documents formatted with it. The advantage of the PS format is that it uses a device-independent playback system (including printer or screen type).

RAF (RAW) is a raster format used in digital cameras and maintains the image directly in the form in which it was captured by the camera sensor. Using this format eliminates artifacts associated with pre-processing of the image by camera software (for example, during JPEG compression) and provides the photographer with the ability to further process photographs (adjust exposure, change color balance, increase size).

Scitex CT is a raster format developed by Scitex; differs slightly from TIFF, with the exception of one feature: on phototypesetting machines (Imagesetter) from Scitex Dolev, files of this format are output somewhat faster. On a PC, file names in the Scitex CT format have the extension *.sct.

SWF (Shockwave Flash) is an internal vector format of the Macromedia Flash program, used for animation on the Internet.

TGA (TrueVision Targa) - a Truevision format developed for color television, supports RLE compression, file names have the *.tga extension.

TIFF (TIF, Tagged Image File Format) is a raster format developed by Aldus Corporation, originally intended for large, high-resolution graphic images obtained by scanning. The format is characterized by high quality of transmission and preservation of the color of the original images. Subsequently, the format was adapted for professional graphics packages and expanded.

WMF (Windows Metafile, Microsoft Windows Metafile) is a metafile format created for use with Windows OS, used for transferring vectors via the clipboard. WMF is supported by almost all programs running under Windows and in one way or another related to vector graphics. Despite its apparent simplicity and versatility, it is recommended to use the WMF format only in extreme cases for transmitting so-called naked vectors. WMF distorts color, does not save a number of parameters that can be assigned to objects in various vector editors, and is not understood by programs targeting the Macintosh PC. WMF files use the *.wmf extension.

VML (Vector Mark-up Language) is a vector format that was submitted to the W3C consortium by Microsoft, Hewlett-Packard, Autodesk, Macromedia, Visio; used on the Internet.

We all know that absolutely all files have their own specific extension. Photos - jpg, music files - mp3 and so on. The file name can be whatever the user wants, but it is not recommended to change the file extension. Sometimes changing the extension can corrupt the file. So be careful about this. Let's look at the most popular file extensions that we come across almost every day:

Archive extensions:

ZIP is a file using ZIP compression, which is supported by almost all archivers.

RAR (Roshal ARchive)– this is already a file using RAR compression. The compression ratio is much higher than ZIP compression.

Video extensions:

AVI– one of the most popular video file extensions. The compression ratio is lower than that of similar video formats. This format is played in almost all video players.

MPEG1-2(MPG)– expansion of audio and video storage with data loss.

MPEG4(MP4)– this format is very often used to transfer files on the Internet.

Graphic extensions:

GIF (Graphics Interchange Format) - format for network distribution. The files are very small in size. Supports animation.

BMP– raster format. The most common graphics format in Windows. Almost all graphics programs can create and read the BMP format. Standard graphics file format for Windows. Almost all Windows image editing programs can create and read BMP files. An image with a .BMP extension cannot be compressed.

JPEG(JPG)– very often used for raster images (drawings, photos). Excellent compression ratio allows for downsizing. But I would like to note that when compressing a file, the quality of the compressed image may be lost. The JPEG format is one of the best formats in the field of photographs and images, as it supports a large number of colors. (16.7 million colors)

PSD (Photo Shop Data)– Photoshop processing format.

TIFF(Tagged Image File Format)– very widely used by digital technology users. It is compressed without data loss, which is a big advantage over other formats. The number of colors is approximately the same as the JPEG format - 16.7 million colors.

Document formats:

DOC– I think this is the most famous format :) Belongs to the Microsoft Word program. Contains both text and graphs, pictures, tables, diagrams, etc.

PDF (Portable Document Format)– This format belongs to an equally well-known program - Adobe Acrobat. Mainly intended for electronic presentation of printed products. To display this format, the free Adobe Reader program is used.

TXT– a document containing unformatted text. In Windows, it is created and opened with a regular notepad.

Music formats:

MP3– the compression ratio is approximately the same as that of the JPG format. But naturally, with strong compression, the sound quality deteriorates significantly.

WAV– a format from Microsoft that is used in Windows. Since this format has large file sizes, it is very inconvenient for transmission over the Internet.

WMA (Windows Media Audio)- another music format from Microsoft for storing audio information. Has a good compression ratio.

Knowledge of file formats and their capabilities is one of the key factors in pre-press preparation of publications, preparation of images for the web and in computer graphics in general.

Yes, today there is no such kaleidoscope of extensions as in the early 90s, when every image editor company considered it its duty to create its own file type, or even more than one, but this does not mean that “everything needs to be saved in TIFF, but compress with JPEG".

Each of the formats established today has undergone natural selection and has proven its viability and necessity. They all have some characteristic features and capabilities that make them indispensable in their work.

Knowledge of the features and subtleties of technology is important for a modern designer, just as it is necessary for an artist to understand the differences in the chemical composition of paints, the properties of soils, types of metals and types of wood.

The main purpose of Knowledge, by and large, is to expand a person’s capabilities, to increase the degree of his freedom, when a person acts as he sees fit, and not as his circumstances force him to do.

Formats:

GIF | JPEG | PNG | TIFF | PostScript | EPS | PDF | Scitex CT | Adobe Photoshop Document | Adobe Illustrator Document | Macromedia FreeHand Document | CorelDRAW Document | PICT |WMF | BMP | RTF

Compression methods:

LZW | JPEG | Huffman | CCITT | RLE (Run Length)

All graphic data in a computer can be divided into two large branches: raster and vector. Vectors are a mathematical description of objects relative to the origin. Simply put, for the computer to draw a straight line, the coordinates of two points are needed, which are connected along the shortest path, the radius is specified for the arc, etc.

Thus, a vector illustration is a set of geometric primitives. Most vector formats can also contain raster objects embedded in the file or a link to a raster file (OPI technology).

The difficulty in transferring data from one vector format to another lies in the use of different algorithms by programs, different mathematics when constructing vector objects and describing raster objects.

OPI (Open Prepress Interface) is a technology developed by Aldus that allows you to import not original files, but their images, creating in the program only a low-resolution copy (sketch) and a link to the original. During the printing process, the sketches are replaced with the original files. Using OPI, instead of simple embedding, makes it possible to save computer resources (primarily memory), significantly increasing its performance. OPI is the primary tool for working with imported graphics files in programs such as FreeHand and QuarkXPress, and is widely used in other products.

A raster file is simpler (to understand, at least). It is a rectangular matrix (bitmap), divided into small squares - pixels (pixel - picture element). Raster files can be divided into two types: those intended for display and for printing.

The resolution of files in such formats as GIF, JPEG, BMP depends on the computer's video system. In old Macs, there were 72 pixels per square inch of screen (screen resolution); on Windows, there was no single standard, but today the most commonly used value is 96 pixels per square inch of screen. In reality, however, these parameters have now become quite arbitrary, since almost all video systems of modern computers allow you to change the number of pixels displayed on the screen.

Raster formats intended exclusively for display have screen resolution only, meaning one pixel in the file corresponds to one screen pixel. They are also printed in screen resolution.

Raster files intended for pre-press preparation of publications have, like most vector formats, the Print Size parameter - the printed size. Associated with it is the concept of print resolution, which is the ratio of the number of pixels per square inch of a page (ppi, pixels per inch or dpi - dots per inch - the term is not entirely correct, but is often used).

Print resolution can be from 130 dpi (for a newspaper) to 300 (high-quality printing), almost never needed anymore.

Raster formats also differ from each other in their ability to carry additional information: various color models, vectors, Alpha channels or spot color channels, layers of various types, leading (interlaced loading), animation, compression capabilities and more.

GIF (CompuServe Graphics Interchange Format)

The hardware-independent GIF format was developed in 1987 (GIF87a) by CompuServe for transmitting raster images over networks. In 1989, the format was modified (GIF89a), support for transparency and animation was added. GIF uses LZW compression, which makes it possible to compress files with a lot of uniform fills (logos, inscriptions, diagrams) well.

The LZW (Lempel-Ziv-Welch) compression method was developed in 1978 by the Israelis Lempel and Ziv and later refined in the USA. Compresses data by searching for identical sequences (called phrases) throughout the file. The identified sequences are stored in a table and are assigned shorter markers (keys). So, if there are patterns of pink, orange, and green pixels in an image that repeat 50 times, LZW detects this, assigns a separate number to that set (for example, 7), and then stores that data 50 times as the number 7. The LZW method also , like RLE, performs better in areas of uniform, noise-free colors, it performs much better than RLE at compressing arbitrary graphics data, but the encoding and decompressing process is slower.

GIF allows you to record an image “through a line” (Interlaced), thanks to which, having only part of the file, you can see the entire image, but with a lower resolution. This is achieved by writing and then loading, first 1, 5, 10, etc. lines of pixels and stretching the data between them, the second pass is followed by 2, 6, 11 lines, the image resolution in the Internet browser increases. Thus, long before the file is downloaded, the user can understand what is inside and decide whether to wait until the entire file is downloaded. Interlaced notation slightly increases the file size, but this is usually justified by the acquired property.

In GIF you can set one or more colors to be transparent; they will become invisible in Internet browsers and some other programs. Transparency is provided by an additional Alpha channel saved with the file. In addition, a GIF file can contain not one, but several raster images, which browsers can load one after another with the frequency specified in the file. This is how the illusion of movement is achieved (GIF animation).

The main limitation of the GIF format is that a color image can only be recorded in 256 colors or less.

JPEG (Joint Photographic Experts Group)

Strictly speaking, JPEG is not a format, but a compression algorithm based not on searching for identical elements, as in RLE and LZW, but on the difference between pixels. Data encoding occurs in several stages. First, the graphics data is converted to a LAB color space, then half or three-quarters of the color information is discarded (depending on the implementation of the algorithm). Next, blocks of 8x8 pixels are analyzed.

For each block, a set of numbers is formed. The first few numbers represent the color of the block as a whole, while subsequent numbers reflect the subtle renderings. The range of details is based on human visual perception, so large details are more noticeable.

In the next step, depending on the quality level you choose, a certain portion of the numbers representing fine details are discarded. The final step uses Huffman coding to more efficiently compress the final data. Data recovery occurs in reverse order.

Thus, the higher the compression level, the more data is discarded, the lower the quality. Using JPEG you can get a file 1-500 times smaller than BMP! The format is hardware independent, fully supported on PC and Macintosh, but it is relatively new and is not understood by older programs (before 1995). JPEG does not support indexed color palettes. Initially, CMYK was not included in the format specifications; Adobe added support for color separation, but CMYK JPEG causes problems in many programs. The best solution is to use JPEG compression in Photoshop EPS files, which is described below.

There are JPEG subformats. Baseline Optimized - files are slightly better compressed, but are not readable by some programs. JPEG Baseline Optimized is designed specifically for the web and all major browsers support it. Progressive JPEG is also designed specifically for the Web, its files are smaller than standard ones, but slightly larger than Baseline Optimized. The main feature of Progressive JPEG is its support for analogue interlaced output.

From the above, the following conclusions can be drawn. JPEG compresses photographic-quality raster images better than logos or diagrams - they have more halftone transitions, and unwanted interference appears among monochromatic fills. Large images for the web or with high printed resolution (200-300 or more dpi) are compressed better and with less loss than with low resolution (72-150 dpi), because in each 8x8 pixel square, the transitions are softer, due to the fact that there are more of them (squares) in such files. It is undesirable to save any images with JPEG compression where all the nuances of color rendering (reproduction) are important, since color information is discarded during compression. Only the final version of the work should be saved in JPEG, because each resaving leads to more and more data losses (discarding) and turning the original image into a mess.

The LAB color space represents color in three channels: one channel dedicated to luminance values (L - Lightnes) and the other two for color information (A and B). Color channels correspond to a scale, not to any one color. Channel A represents a continuous spectrum from green to red, while channel B represents a continuous spectrum from blue to yellow. The average values for A and B correspond to real shades of gray.

There is a similar YCC color model used in Kodak Photo CD and FlashPix formats not covered here.

The Huffman compression method was developed in 1952 and is used as a component in a number of other compression schemes, such as LZW, Deflation, JPEG. The Huffman method takes a set of symbols and analyzes them to determine the frequency of each symbol. The most frequently occurring characters are then represented in the smallest possible number of bits. For example, the letter "e" is most often found in English texts. Using Huffman encoding you can represent "e" with just two bits (1 and 0), instead of the eight bits needed to represent the letter "e" in ASCII.

PNG (Portable Network Graphics)

PNG is a relatively recently developed format for the Web, designed to replace the outdated GIF. Uses Deflate lossless compression, similar to LZW (it was because of the patenting of the LZW algorithm in 1995 that PNG arose). Compressed indexed PNG files are usually smaller than similar GIF files, and PNG RGB is smaller than the corresponding TIFF file.

PNG files can have any color depth, up to 48 bits. Two-dimensional interlacing is used (not only rows, but also columns), which, just like in GIF, slightly increases the file size. Unlike GIF, where transparency is like honey - either it is there or not, PNG also supports translucent pixels due to the Alpha channel with 256 shades of gray.

The PNG file records gamma correction information. Gamma is a certain number that characterizes the dependence of the brightness of your monitor screen on the voltage on the electrodes of the kinescope. This number, read from the file, allows you to enter a brightness correction when displaying. It is needed so that the picture created on Mac looks the same on Windows and on various UNIXes. Thus, this feature helps to implement the main idea of WWW - the same display of information regardless of the user's equipment.

PNG is supported in Microsoft Internet Explorer version 4 on Windows and version 4.5 on Macintosh. Netscape added PNG support to its browser in versions starting with 4.0.4 for both platforms. However, support for important format features such as seamless transparency and gamma correction has not yet been implemented.

TIFF (Tagged Image File Format)

The hardware-independent TIFF format appeared as an internal format of the Aldus PhotoStyler program. Its modular architecture turned out to be so successful that, having successfully survived the death of its native program, TIFF continues to improve and develop today.

Today it is one of the most widespread and reliable; it is supported by almost all programs on PC and Macintosh in one way or another related to graphics. Generally, TIFF is the best choice when importing raster graphics into vector programs and publishing systems. It has a full range of color models available from monochrome to RGB, CMYK and additional solid colors. TIFF may contain clipping paths, alpha channels, layers, and other additional data.

The exception, to some extent, is FreeHand. Sometimes TIFF files in it can randomly change their location when creating a PostScript file or directly in the document when opening it. More often than not, TIFFs “jump” while in the clipping path. With FreeHand, it is still preferable to use EPS.

TIFF can be saved in two recording orders: Macintosh and PC. This is because Motorola processors read and write numbers from left to right, while Intel processors read and write numbers the other way around. Modern programs can use both formats without problems.

In the TIFF format, it is possible to save using several types of compression: JPEG, ZIP, but, as a rule, only LZW compression is used. A number of older programs (eg QuarkXPress 3.x, Adobe Streamline, many text recognition programs) cannot read compressed TIFF files, but if you are using newer software there is no reason not to use compression.

Adobe PostScript

PostScript is a page description language (laser printer control language) from Adobe. It was created in the 80s to implement the WYSIWYG (What You See is What You Get) principle. Files of this format are a program with execution commands for an output device. They have the extension .ps or, less commonly, .prn and are obtained using the Print to File function of graphics programs when using a PostScript printer driver.

Such files contain the document itself (only what was located on the pages), all associated files (both raster and vector), the fonts used, as well as other information: color separation boards, additional boards, screen lineature and raster dot shape for each board and other data for the output device. If the file is created correctly, it does not matter what platform it was made on, whether True Type or Adobe Type 1 fonts were used - it makes no difference.

However, you need to take into account that even if you have made the correct settings in the print window, problems may arise due to the incorrect translation of the graphic language program you are using into the PostScript language (for example, the introduction of information about unused fonts). The most correct PS files are created by Adobe programs.

Data in a PostScript file is usually written in binary encoding. Binary code takes up half the space of ASCII. ASCII encoding is sometimes required for transferring files over networks, for cross-platform sharing, and for printing over serial cables. In these cases, the binary encoding may become corrupted (making the file unreadable) or cause "strange" behavior by the file server. These problems have long been eliminated in modern systems, but older computers and servers are susceptible to them.

The above applies to all PostScript-based formats: EPS and PDF, which are described below.

A more detailed description of the PostScript language, its features, problems and methods of printing from various programs can be found on my website in the article “Non-scary PostScript”.

EPS (Encapsulated PostScript)

The Encapsulated PostScript format can be called the most reliable and universal way to save data. It uses a simplified version of PostScript: it cannot contain more than one page in one file, and does not save a number of printer settings. Like PostScript print files, EPS records the final work, although programs such as Adobe Illustrator and Adobe Photoshop can use it as a working document.

EPS is designed for transferring vectors and rasters to publishing systems and is created by almost all programs that work with graphics. It makes sense to use it only when the output is carried out on a PostScript device. EPS supports all color models necessary for printing, among them, such as Duotone, it can also record data in RGB, clipping path, trapping and raster information, embedded fonts. In EPS format, data is saved on the clipboard (Clipboard) of Adobe programs for exchange among themselves.

You can save a sketch (image header, preview) along with the file. This is a low-resolution copy in PICT, TIFF, JPEG or WMF format that is saved with the EPS file and allows you to see what's inside, since only Photoshop and Illustrator can open the file for editing. All others import the sketch, replacing it with original information when printed on a PostScript printer. On a printer that does not support PostScript, the sketch itself is printed. If you work on Photoshop for Mac, save thumbnails in JPEG format; other Mac programs save thumbnails in PICT format.

These and JPEG thumbnails cannot be used by Windows applications. If you're working on a PC or don't know where the file will be used, save the sketch in TIFF format (when given the choice). CorelDRAW also offers the vector format WMF for sketches, you should use this Microsoft brainchild very carefully - it will not lead to any good.

Initially, EPS was developed as a vector format, later its raster version appeared - Photoshop EPS. In addition to the thumbnail type (TIFF, PICT, JPEG), Photoshop allows you to choose the data encoding method. ASCII, Binary and JPEG. The first two were described above; JPEG is worth focusing on.

Photoshop allows you to compress raster data using the JPEG algorithm. Adobe has improved this compression method. Photoshop's JPEG now supports CMYK and compresses better than JPEG that fully complies with the original specifications. In other words, JPEG-encoded non-thumbnail EPS files weigh less than comparable JPEG files! However, I would like to draw your attention to an important feature when working with JPEG compression in EPS.

Printer and phototypesetting drivers cannot perform color separations on such files. That is, when performing color separation on your computer, the JPEG-compressed EPS image will appear entirely on the first board (Cyan, usually). However, in the service bureau, Scitex workstations (the majority of them in Israel) can color separate pages with JPEG EPS illustrations without any problems. I think systems from other companies also support JPEG EPS, in any case it’s worth asking. In service bureaus and printing houses in Tel Aviv, I was often recommended to use JPEG EPS instead of TIFF for recording raster data, since it is faster to output.

EPS has many varieties, depending on the creator program. The most reliable EPS are created by programs produced by Adobe Systems: Photoshop, Illustrator, InDesign. Since 1996, Adobe programs have a built-in PostScript interpreter so they can open and edit EPS. This opportunity seems to me very important. Other graphic editors cannot open EPS; moreover, the EPS files they create sometimes turn out to be, to put it mildly, special.

Among the most problematic are Quark EPS, created by the Save Page As EPS function, and FreeHand editable EPS, created by the Save As function. You should not particularly trust Corel EPS versions 6 and lower and EPS from CorelXARA. EPS files from CorelDRAW 7 and higher still have the problem of adding fields to the Bounding Box (a conditional rectangle in PostScript that describes all objects on the page).

Before exporting EPS files from CorelDRAW, CorelXARA and, to a lesser extent, FreeHand, it is worth converting many program effects (translucent fills, for example) into raster or simple vector objects. Thick outlines (more than 2 pt) may also make sense to be converted into objects when the program provides such an opportunity. You can check the EPS file with Adobe Illustrator, if it opens, then everything is in order.

PDF (Portable Document Format)

PDF is proposed by Adobe as a platform-independent format for creating electronic documentation, presentations, and transferring layouts and graphics over networks. Used as an internal graphics format in Mac OS X.

PDF files are created by converting from PostScript files or using the export function of a number of programs. Adobe Acrobat Distiller is used for conversion; this is the best way to create PDF. Creating PDFs using the export method from programs usually gives worse results - the files are heavier and often have problems with embedding fonts.

To create PDF, there is also a PDFWriter program that works as a virtual printer. PDFWriter is not PostScript based and cannot handle graphics correctly. It is designed for quickly producing simple text documents. It has the same problem with embedding fonts as many programs that can export PDF. The most reliable and closest to the original PDF is created from PostScript and EPS files by the Acrobat Distiller program, supplied in the Adobe Acrobat package.

PDF was originally designed as a compact electronic documentation format. Therefore, all data in it can be compressed, and different types of compression are applied to different types of information, the most suitable for them: JPEG, RLE, CCITT, ZIP (similar to LZW and also known as Deflate). The Acrobat Exchange 3 program (which in version 4 became simply called Acrobat 4.0) allows you to create hyperlinks, fill in fields, include video and sound in a PDF file, and other actions.

The CCITT (International Telegraph and Telephone Committie) compression method was developed for facsimile transmission and reception. It is a narrower version of Huffman coding. CCITT Group 3 is identical to the fax message format, CCITT Group 4 is the fax format, but without special control information.

The PDF file can be optimized. Repeating elements are removed from it, a page-by-page order is established for loading pages via the web, with priority first for text, then graphics, and finally fonts. However, when there are no duplicate elements, the file, after optimization, usually increases slightly.

PDF is increasingly being used to transmit graphics and layout over networks in a compact form. It can retain all the output device information that was in the original PostScript file. This applies to PDF versions 1.2 (Acrobat 3) and higher. However, version 1.2 cannot include trapping information, some other specific data (DSC, for example), and does not use color profiles. All this is implemented in subsequent versions of the format.

You can find a more detailed description of technologies based on Adobe Acrobat PDF on my website in the article Man-Orchestra 3.0.

Scitex CT

A PostScript file intended for output goes through a number of stages on its way to the phototypesetting machine. The most important of these is rasterization - the process of converting PostScript data into a bitmap, performed by the PostScript interpreter (RIP).

CorelDRAW format files can be used to transfer/transfer works to a PC, but it is not advisable to import them into layout programs. On a Macintosh, CorelDRAW for Windows files open with the Macintosh version of CorelDRAW and Adobe Illustrator 8 or later.

PICT (Macintosh QuickDraw Picture Format)

PICT is a native Mac OS Classic format. Standard for the clipboard, uses the Mac OS graphical language. PICT is capable of carrying raster, vector information, text and sound, and uses RLE compression. Supported on Mac by all programs. Pure bitmap PICT files can have any bit depth (from Lineart to CMYK).

Vector PICT files, which have all but disappeared from use these days, had strange problems with line thickness and other printing variations.

The format is used for the needs of Mac OS, and when creating certain types of presentations only for Macintosh. Outside the Macintosh, PICT has a .pic or .pct extension and can be read by separate programs, but working with it is rarely simple and straightforward.

WMF (Windows Metafile)

The WMF vector format uses the Windows graphic language and can be said to be its native format. Used to transfer vectors via the clipboard. Understood by almost all Windows programs that are somehow related to vector graphics.

However, despite its apparent simplicity and versatility, the WMF format should be used only as a last resort for transmitting bare vectors. WMF distorts color, cannot save a number of parameters that can be assigned to objects in various vector editors, cannot contain raster objects, and is not understood by many Macintosh programs.

BMP (Windows Device Independent Bitmap)

Another native Windows format. It is supported by all graphic editors running this operating system. It is used to store bitmap images intended for use in Windows and, in fact, is not suitable for anything else.

Capable of storing both indexed (up to 256 colors) and RGB colors (more than 16 million shades). It is possible to use compression based on the RLE principle, but this is not recommended, since many programs do not understand such files (they may have the .rle extension). There is a version of the BMP format for the OS/2 operating system.

Using BMP for purposes other than Windows is a common mistake for newbies. It is important to understand that it is not advisable to use BMP either on the web, or for printing (especially), or for simply transferring and storing information.

RTF (Microsoft Rich Text Format)

The RTF text format came here for its extraordinary ability to transfer texts from one program to another. It allows you to transfer formatted text from optical character recognition programs or text editors to graphics programs or in any other direction. RTF can be a good solution (and sometimes the only solution) when transferring non-Latin, for example, Hebrew text or Russian in Windows 95/98 Hebrew Edition from program to program.

The secret to compatibility is the use of special RTF and Unicode formatting tags. It is Unicode (used as the basis of the Microsoft Word 97/98 format for Macintosh and PC) that allows you to easily transfer Russian texts from PC to Mac and back in MS Word 97/98 files (true for higher versions of Word).

RTF is used as the main one in the TextEdit editor that comes with Mac OS X and in the WordPad program that comes with Windows.

The abundance of images used on computers can be divided into three large groups. First of all, 2D graphics, in which flat (without a third coordinate) images are created; this group includes raster and vector graphics. Then 3D graphics and motion graphics.

Since images are created using special tools - graphic editors - it is impossible to consider file formats without taking into account their features. First of all, what is a graphics file? In the most general case, this is the system of image information adopted in a given graphics editor and the method of saving (recording) it. Such an information system can contain both general data (representation of an image on a particular display device, size, resolution, type of printer for printing, degree and method of information compression), and data that is specific and unique. Such data is created during the image editing stage and is intended for subsequent use during editing. For example, CorelDraw files contain information about curves, Photoshop files contain information about layers, channels, etc. Each graphic editor encodes this information in a certain way when recording (saving) on a medium. Thus, the graphic file format should be understood as a set of information about the image and the method of recording it in the file. In general, all graphic formats can be divided into two groups. General-purpose formats contain only the image itself and are intended for storing, transferring or viewing images (gif, tiff, jpeg, etc.) and specific formats intended for storing intermediate results of image editing (cdr, cpt, psd, ai, etc.).

Let us dwell in more detail on the 2D group due to its greatest prevalence. A raster graphics image is an ordered array of unit elements (pixels for a monitor or dots for a printer) containing color information. The number of such elements is determined by the image size and resolution, and the file size additionally depends on the color palette used (black and white or 1-bit, grayscale and 256 colors or 8-bit, high color or 16-bit, true color or 24-bit ). Vector graphics contain mathematical descriptions of the curves and fills (areas filled with a single color and areas of gradients) that make up an image. The issue of resolution and color palette is decided immediately before the file is output to a specific physical device and taking into account its characteristics. In the printing industry, this process is known as RIP - rasterizing an image process.

File compression. Since graphic files tend to be large, the ability to compress (pack) information is useful. There are currently two known compression methods - lossless and lossy. Lossless compression algorithms are similar to those of conventional archivers (LZH, PKZIP, ARJ). The most famous of them, LZW (LZ84), is widely used in the popular raster formats GIF and TIFF. Lossy compression algorithms discard information that is not perceptible to humans (JPEG, PCD). The degree of compression in this case is much higher, but occurs more slowly and can lead to deterioration in quality (depending on the selected compression ratio). The main disadvantage of this algorithm is the impossibility of recompression without significant loss of the original image quality. Therefore, it is recommended to save only the final editing results in JPEG format, and in no case intermediate ones.

General purpose formats

Microsoft Windows Bitmap (BMP)

A format for storing raster graphics in a Microsoft Windows environment (for example, screen wallpapers and screensavers). Supports 1-, 4-, 8-, 24-bit color. Allows compression without loss of quality.

Kodak Photo CD (PCD).

The developer is Kodak. The format is intended for storing slides and negatives captured using a Kodak Photo CD type camera. Each file stores 5 copies of one image of different sizes and qualities from 192x192 to 3072x2048 pixels. It is impossible to programmatically record a PCD image on a computer; you can only import the image into a graphics editor that supports this format.

Zsoft PC PaintBrush (PCX)

One of the oldest and most famous formats for storing raster graphics. It appeared almost along with personal computers, due to which it is the most common and is supported by almost all image viewing/editing programs. Uses the simplest lossless compression algorithm RLE.

Tag Image File Format (TIFF)

Developers: Aldus and Microsoft. A universal format for storing raster graphics, widely used in publishing. It is necessary to make a reservation that there are quite a lot of its varieties, due to different compression algorithms. The format that uses the LZW algorithm has the greatest compatibility. The format supports 24 and 32-bit color (CMYK), two types of recording IBM PC and Macintosh, and can store information about masks (selected areas of the image).

TrueVision TGA (TGA)

Developed by TrueVision. The format is used for storing raster graphics and has an interesting feature - along with support for 24-bit color, it has another 8 bits for each single image element to store additional information. In particular, it may contain a mask, which is used in video editing programs, for example, to create an overlay of two sequences of frames. It has been known for a long time and is supported by many graphics packages.

Graphics Interchange Format (GIF)

Developed by CompuServe Corporation in 1987 for storing raster graphics. Implemented one of the most effective LZW compression methods for its time (87g). Allows you to display an image on the screen in four passes, allowing you to preview the image before its final drawing. In 1989, a new version of GIF 89a appeared. This format supports saving multiple images, animation sequences, and transparency colors in one file for the purpose of overlaying images on top of each other. Still widely used to store and transmit small images (page design elements) to the World Wide Web.

Joint Photographic Experts Group (JPEG)

The raster format owes its popularity to the high degree of compression of the source image, based on a lossy compression algorithm. However, this applies primarily to 24- and 8-bit images. There are several varieties, due to different compression algorithms and display methods (gradual rendering is similar to gif). Also widely used on the WWW, mainly for transmitting large images.

Specific formats

As mentioned above, this group of formats is intended mainly for “internal” use (storing intermediate results of image editing). In addition to information about the image itself, the files contain a lot of service data that cannot be correctly interpreted by other viewing/editing programs. Such data may include information about fonts, layers, selections (masks), curves, special effects, etc. The most common formats are for vector graphics - cdr (Corel Draw) and ai (Adobe Illustrator), for raster graphics - psd (Adobe Photoshop ) and cpt (Corel PhotoPaint). Typically, the final image (ie the image intended for publication) is imported into one of the general purpose formats depending on the purpose of publication (gif or jpeg for the Internet, tiff for publishing systems, etc.).

Igor Sivakov