Images are stored in a variety of file formats. Many different image file formats have been developed over the years for specific applications and hardware. Most applications support a large number of commonly used file formats.

WHAT TO USE

MOST POPULAR FORMATS

BMP - Windows Bitmap

The Windows Bitmap file format is the standard file format used by Microsoft Windows. Bitmap files can contain either 2 (black and white), 16, 256 or 16.7 million colors. Most Windows Bitmap files are not compressed. It is possible to save 16 and 256 color images in a compressed format (See Run-Length Encoded below) but some applications are not able to read the compressed files. The default file extension for Windows Bitmap files is “.BMP”. Occasionally you may see bitmap files with the extension “.DIB”.

RLE - Windows Run-Length Encoded

The RLE format is a variation of the Windows BMP format that offers a modest degree of image compression. It has two primary uses under Windows. It can be used to create compressed wallpaper files and it can be used to replace the opening Windows logo screen with a file of your own choosing. RLE files are always either 16 or 256 color image files.

GIF - CompuServe Graphics Interchange Format - Indexed color 1 to 8 bits

The GIF file format was developed by CompuServe Inc. for use on their online service and became the number one choice for Web pages until royalty claims were introduced. GIF files are color-mapped files that can have anywhere from 2 to 256 colors. Most applications support both the 87a and 89a versions of the GIF standard. GIF files are always compressed and offer an efficient way to store large images.

JPG - Joint Photographic Experts Group - RGB 24, grayscale 8 bits

The JPEG format uses a method of compression that reduces image file size by selectively reducing the amount of detail contained in the image and by transforming the image data into a format that is better suited for compression. Images with fewer details compress extremely well, while pictures with a high degree of random detail do not compress as well, or suffer some degree of image degradation. The relative amount of detail removed can be specified in most applications. At the default value of 75, relatively little picture degradation will take place, but a significant amount of compression will be obtained. At lower values you will experience still better compression, but with a marked loss of image quality. JPEG images are either true color or grayscale (256 shades of gray).

PCD - Kodak Photo CD

The Photo CD format is a proprietary format developed by Eastman Kodak to store digitized photographic images on CD-ROM disks. These images are always converted to true color (24-bit) images when loaded into MGI PhotoSuite. Photo CD CD-ROM disks produced according to Kodak specifications include one or more Photo CD images as well as an overview file containing small “thumbnail” versions of each image on the disk. The Photo CD image files always reside in a directory named d:\PHOTO_CD\IMAGES on a Photo CD disk. However, you may also encounter Photo CD image files on networks, bulletin boards and other types of CD-ROM disks which lack the overview file.

Each Photo CD file contains a number of scans of the same image at a number of different resolutions. Many applications support the following Photo CD resolutions: 192x128 pixels, 384x256 pixels, 768x512 pixels, 1536x1024 pixels and 3072x2048 pixels. If you only have four megabytes of memory installed in your computer, you may not have sufficient free memory to edit the 1536x1024 or 3072x2048 pixel Photo CD formats.

TGA - Truevision Targa

The Truevision Targa format was originally developed by Truevision Inc. for use with their line of graphic display cards. The Targa format is used by several high-end paint and CAD programs. Color resolutions range from 256 color, 32768 (16-bit) color, 24-bit true color and 32-bit true color formats. The 32-bit Targa format contains 24 bits of color data as well as 8 bits of transparency (overlay) data. Targa images exist in both compressed and uncompressed formats.

PCX - PC Paintbrush

PCX files were originally developed for Z-Soft’s PC Paintbrush package. These files come in monochrome, 16 color, 256 color and true color (24-bit) varieties. PCX files are compressed using a method that offers a modest degree of compression compared to other compression formats.

TIF - Tagged Image File Format - RGB 24 or 48 bits, grayscale 8 or 16 bits, indexed color 1 to 8 bits, line art (bilevel) 1 bit

The TIFF format was developed by Microsoft and Aldus Corporations as a portable method of storing bitmap images. TIFF files come in monochrome, 16-color, 256-color, 16-color grayscale, 256-color grayscale and true color (24-bit) varieties. TIFF files exist in both compressed and uncompressed formats. The compression format offers a high degree of compression. TIFF image files use LZW lossless compression which means there is no quality loss due to compression. However, certain older paint programs that use an early version of the TIFF format may have difficulty reading compressed TIFF files. If you find that a program will not read the compressed files, try saving the file in the uncompressed format. The default file extension for TIFF files is “.TIF”.

CTF - MGI Catalog File

The CTF format was developed by MGI as a means to store thumbnails for cataloging images and multimedia files. Thumbnails of images can be either 256- or 16-million colors and one of any nine sizes, allowing great flexibility in size vs. quality vs. performance.

PNG - Portable Network Graphics - RGB 24 or 48 bits, grayscale 8 or 16 bits, indexed color 1 to 8 bits, line art (bilevel) 1 bit

The original purpose of PNG was to be a royalty-free GIF and LZW replacement. PNG supports a large set of technical features, including superior lossless compression from LZ77. Compression in PNG is called the ZIP method, and is like the 'deflate" method in PKZIP (royalty free). PNG incorporates special pre-processing filters that greatly improve the lossless compression efficiency, especially for gradient data found in 24-bit photos. PNG has additional unique features, f.e. an Alpha channel for a variable transparency mask (partial transparency can be used for many things such as fades and anti-aliasing of text), and an embedded Gamma value so image brightness can be viewed properly on Windows and Mac screens. PNG has a much smaller file size than TIF LZW. PNG is an excellent replacement for GIF and 24-bit TIFF LZW files. PNG is superior to GIF. It produces smaller files and allows more colors.