IntraNet, 1/26/98

Use these format snapshots for determining which best suits your image.

GIF:

• Lossless for images with 256 colors or less.
• Works best for art with flat colors and sharp edges.
• Remove vertical banding in an image, since horizontally oriented bands of color compress better than their vertical counterparts.
• Don’t introduce visual noise – i.e., random pixels that break up blocks of solid color.
• Avoid the dithering technique of using a group of different colored pixels to simulate a color. It breaks up rows of color that can be minimized.

• Little or no loss in image quality for continuous tone at low compression ratios and fair for flat color, sharp-edged art and black-and-white images.
• Medium compression ratios are most suitable for continuous tone images on the Web.
• High compression ratios give poor quality. They are only suitable for thumbnails and previews.
• Avoid using for images with blocks of a single color.

• Images are 10% to 30% smaller than GIF images.
• Supports gray scale up to 16 bits per pixel and true color up to 48 bits per pixel, with up to 32 bits color with 16 bits of alpha data. This allows for up to 64,000 levels of transparency.
• Avoid introducing vertical detail or visual noise.
• Avoid dithering.

Image format	GIF	PNG	JPEG
Minimum compression	4:1	5:1	10:1, 30:1, 60:1
Maximum compression	10:1	15:1	20:1, 50:1, 100:1
Lossless	Yes*	Yes	No for all three
Maximum palette	8 bit	48 bit	24 bit
Use for line art	Good	Good	OK, good, very good
Use for continuous tone	Poor	Poor	Very good, good, fair
Supports an alpha channel **	Yes**	Yes	No
Support for multiple channels	Yes	No	No
Use for animation	Yes	No	No
Provides error correction	Yes	No	No

* For images with palettes of 256 or fewer colors.
** Transparency.
*** Implemented as a simple binary transparency (fully opaque or fully transparent) for a single palette entry.