File Formats

If a color modes is a way of describing a digital image, a file format is a way of storing that information on a disk. There are a mid-numbing variety of file formats. The table below addresses a few of the most important for the aspiring Web author.

See also: GIF vs. JPEG

Format Web ready? Bit-depth Color modes Compression Transparency Typical uses
GIF Yes Up to 8-bit indexed, grayscale Lossless Simple Cartoons, logos
JPEG Yes Up to 24-bit1 RGB, grayscale, CMYK1 Lossy None Photo- realistic images
PNG Yes, but... Up to 32-bit (24-bit plus alpha channel) bitmap, grayscale, RGB Lossless Complex ???
Native varies
TIFF No Up to 32-bit (24-bit plus multiple masking channels) bitmap, grayscale, indexed, RGB, CMYK, LAB Optional, lossless None Inter- application exchange, archiving
PICT No Up to 32-bit (24-bit plus masking channel) bitmap, grayscale, indexed, RGB Optional, lossy None Macintosh exchange
BMP No up to 24-bit bitmap, grayscale, indexed, RGB Optional, lossless None PC exchange


1 Caution: Some versions of the JPEG format can handle 32-bit, 4-channel (CMYK) color, but this is not compatible with the Web's RGB environment.

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