• 1 bit per pixel refers to an image with 2 colors.
• 4 bits per pixel refers to an image with up to 16 colors.
• 8 bits per pixel refers to an image with up to 256 colors.
• 16 bits per pixel refers to an image with up to 32,768 colors.
• 24 bits per pixel refers to an image with up to 16,777,216 colors.

BMP

(Bit-Map)

BMP is the standard MS-Windows raster format.
(BMP files can be created with Windows' Paintbrush and used as "wallpaper" for the background when running Windows. See your Windows manual about using BMP files as wallpaper.)
Windows uses a fixed color palette for BMP files which cannot be changed, as doing so would make the screen and border colors change too. This means that transferring an image to the BMP format may result in some color shifts when BMP files are imported into Windows applications.

BMP-Windows-RLE format supports 4, 8 bits per pixel - RLE compression.

DIB

(Device Independent Bitmap)

DIB files are applied mainly in computer multimedia systems.
They can also be can be used as image files in the Windows environment.

DIB-Windows-RLE format supports 4, 8 bits per pixel - RLE compression.

RLE

(Run Length Encoding)

GIF

(Graphics Interchange Format)

The CompuServe GIF is commonly used to upload documents to the CompuServe Information Service and to pass documents between other types of computers. The idea behind designing GIF files was to create the smallest possible image file for uploading and downloading from electronic Bulletin Board Systems (BBS), thus producing a highly compressed format that minimizes file transfer time over phone lines. The compression is accomplished by using the LZW method for indexed color tables.
There are two GIF file versions: 87a and 89a.
Both versions may use an encoding method referred to as interlacing. When an image is saved by using four passes instead of just one, it is called interlacing. On each pass, certain lines of the image are saved to the file. If the program decoding a GIF file displays the image as it is decoded, the user will be able to see the four passes of the decoding cycle. This will allow the user to get a good idea of what the image will look like before even half of the image is decoded. Most communication programs (for BBSs and the InterNet) allow the user to download GIF files and view them as they are downloaded. If the image is interlaced, the user will be able to decide if the image is one they like before half of the download is complete. If the user does not like the image, the download can be aborted. This results in the saving of time and money for the person downloading the image.
GIF files may contain multiple images.

GIF - version 89a Interlaced supports 1, 4, 8 bits per pixel.

IMG

IMG files were originally designed to work with the GEM Paint Program.
IMG files handle monochrome and gray level images.
The VENTURA Publisher application, working in the same GEM environment, also supported the IMG file format.
In order to maintain compatibility, various other desktop publishing applications have added support for importing and exporting this format (although usually not processing it).

Some applications read only 1 bit per pixel in both the new and old IMG styles.

MAC

(Macintosh Paint)

MAC files are used in the Macintosh MacPaint application.
The MAC format file has 2 basic options:
* The common option is a ported MacPaint files,that includes a "MacBinary" header.
* The rare option is the one used with PFS First Publisher,this file has no header.
In order to migrate a MAC file from a Macintosh to a PC, a "MacBinary" header has to be added to the file format. MAC images can be transferred "back" from a PC to a Macintosh. Unless you have a specific PC application that requires no header, the MAC files should be saved with a header.
The MAC format requires always an image width of 576 pixels and a height of 720 lines. For that reason files converted to the MacPaint format from other formats will be cropped or padded out as necessary to fit in the 576X720 pixels size.
MAC file format supports only 1 bit per pixel, meaning that Only monochrome files can be converted to MacPaint files.

MAC- with a header format supports 1 bit per pixel.

MSP

(MicroSoft Paint)

PCX

PCX format, established by Zsoft for its PC Paintbrush software, is commonly used by IBM compatible computers.
With no standard to the industry, this format became the standard by default. This format is supported by more applications than any other format.
Version 3 does not contain palette information. Some applications will override this by using the default VGA colors used by Windows as the palette. This may result in a different looking images when using different viewers.
Most PC software support version 5 of the PCX format.

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In order to allow older applications the ability to read PCX files use the lowest version possible.
On the other hand, some applications do not have add support for versions 0, 2, and 3. If you are using such an application - save your images as a version 5.

PCX - version 5 format supports 1, 4, 8, 24 bits per pixel.

PIC

(Pictor)

PIC format files are generated and used by PICTOR, PC-Paint and GRASP.
This PIC file format is not compatible with the Lotus 1-2-3 PIC drawing files !
16 color PIC files have a non-common structure in their color manifestations. For this reason, graphic applications (rather then the 3 mentioned above) will produce a temporary scratch file while packing or unpacking a 16 color PIC file.

PIC - PC Paint format supports 4 bits per pixel.

TGA

(Targa)

RAS

(RASTER)

RAS files are generated in a raster format by Sun Microsystems computers.
There are three types of RAS files:
* Type 0 - Old Style.
* Type 1 - Modern Style.
* Type 2 - Experimental.
 

RAS - type 1 - Modern Style format supports 1, 8, 24, 32 bits per pixel.

WPG

(WordPerfect Graphic File)

WPG file format is used by WordPerfect.
It first appeared with the release of WordPerfect 5.0, and with the release of version 5.1, the format was changed accordingly. It is advised to use the same format version as the version of WordPerfect in which the image will be used. These files can contain bitmaps, line art, and vector graphics. When using an application rather then WordPerfect for viewing a WPG file containing both bitmapped and vector elements, the vector elements will be discarded.
Note that the WPG specification allows files of up to 256 colors, but WordPerfect itself would not read files of more than 16 colors !

WPG - version 5.1 format supports 1, 4, 8 bits per pixel.

IFF

(Amiga Interchange File Format)

LBM

CE

PIXAR

The PIXAR format is designed specifically for exchanging files with PIXAR image computers.
PIXAR workstations are designed for high-end graphics applications, such as work involving three-dimensional images and animation.
There are no format options associated with the PIXAR file format.

PixelPaint

The PixelPaint file format allows a document to be opened in the PixelPaint and PixelPaint Professional graphics applications.
You should only use this format for writing files for PixelPaint versions 1.0 and 2.0, as PixelPaint Professional no longer allows a document to be saved in this format.
This format allows you to specify the image size (canvas). It also enables you to decide whether you want the image to appear in the center or in the upper left corner of the canvas when the document is opened.

JPEG

(Joint Photographic Experts Group)

JPEG compression economizes on the way data is stored and also identifies and discards extra data, that is, information beyond what the human eye can see.
Because it discards data, the JPEG algorithm is referred to as "lossy". This means that once an image has been compressed and then decompressed, it will not be identical to the original image. In most cases, the difference between the original and compressed version of the image is indistinguishable.
In general, compressed JPEG images have compression ratios of between 5:1 and 15:1. A trade-off does exist between the image quality and the amount of compression. You do not need to decompress images saved in the JPEG format. They are automatically decompressed when they are opened.

JAS

The JAS format files were designed to create the smallest possible image files for 24 bits per pixel color images and 8 bits per pixel gray scaled images. JAS uses a discrete cosine transformation to alter the image data and then compress that data. This process results in a substantial reduction of the file size when the image is saved to the disk. This method is referred to as "lossy": saving and retrieving an image using the JAS file format will result in some loss of image data. The amount of loss is dependent on the compression level that you have selected in your application. By using the lowest possible value for the file compression you will have the least amount of loss.

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Whenever you save an image as a JAS file, you should immediately load the image that was just saved. Check to make sure the amount of data loss is acceptable before deleting your original image.

JAS (gray scale) format supports 8 bits per pixel.

TIFF

(Tagged-Image file Format)

EPS

(Encapsulated PostScript)

The Encapsulated PostScript file (EPS) format is supported by most illustration and page layout programs, and in most cases is the preferred format for these applications.
Note that this is also the only file format that supports transparent whites in Bitmap mode.

Raw

The Raw format is a flexible file format for transferring documents between different applications and computer platforms.
Raw format consists of a stream of bytes describing the color information in the file. Each pixel is described in binary format, where 0 equals black and 255 equals white.

Scitex CT

(Scitex Continuous Tone)

The Scitex CT format is available for CMYK color images and grayscale images.
Scitex computers are used for high-end image processing.

CUT

CUT file format is definitely the most awkward format.
CUT files do not "know" how many colors they have in them !
They rely on a second accompanying file, called a PAL file, to define their colors. Most applications will search for the PAL file in order to determine whether the CUT file has two or eight bits of color. If there is no PAL file with the same name as the CUT file, the CUT file is treated as 2 colors. Files saved to the CUT format from various applications will appear as two color files if they were recognized that way or as 256-color files if they had more than two colors initially. Note that a 256 color file, with a missing PAL file will eventually end up as a 2 color file !