Wednesday, December 8, 2010

Gif, Jpg and Png Information

GIF is great for computer generated images with limited palettes
JPG is far better for photographs. It gives better quality images for the same file size
The GIF file is 2.4 times bigger than the JPG, but is clearly of lower quality
Note the use of pixel dithering to try to match the color gradations in the shirt
the file size of the JPG on the left is 18 times smaller than that of the GIF on the right.
Use GIF when there are large areas of uniform color and the total number of colors is smaller than 256
The JPG image above is seriously degraded
As all recent browsers now support the PNG format, it is time to abandon GIF for most purposes.
PNG is not limited to 256 colors as is GIF. The only reason to use GIF is for images with transparency. PNG has superior transparency, but unfortunately Microsoft refuses to fix a bug in Internet Explorer's treatment of PNG transparency. So to reach the widest audience, use PNG only for images without transparency.
GIF does significantly better on images with only a few distinct colors, such as line drawings and simple cartoons.
JPEG has a hard time with very sharp edges: a row of pure-black pixels adjacent to a row of pure-white pixels, for example. Sharp edges tend to come out blurred unless you use a very high quality setting. Edges this sharp are rare in scanned photographs, but are fairly common in GIF files: borders, overlaid text, etc. The blurriness is particularly objectionable with text that's only a few pixels high. If you have a GIF with a lot of small-size overlaid text, don't JPEG it.

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