WEB MEDIA SCHOOL session 52 - JPEG vs GIF
I crunched my JPEG and it got larger. How come? 1. Your image was already saved at a low quality level using a poor JPEG compressor. 2. Your image was already optimized. 3. You are trying to optimize the image at too high a quality level. 4. Your image is very noisy - lots of little dots and snow obscure the image. In some cases you will need to start over with a clean source image .
I saved my JPEG as a GIF and it got smaller. Should I always use GIF? - GIF might be a good choice if: - small in dimensions (under 250 x 250) - mostly flat areas of color - logos, icons, etc - not a lot of different colors (less than 32) - parts of the image need to be transparent - no gradients (gradually shaded color transitions) - lots of text, particularly small text - fine detail that must be preserved at all costs - or it needs to be animated
JPEG might be a good choice if: - natural image or photo - no transparency - no animation - rich color content - or fine detail and textual content are less important.
If you are converting from one format to another, it's almost always best to convert directly from a source image that hasn't already been compressed. JPEG artifacts can make it hard to compress properly as a GIF, and saving a GIF as a JPEG may not provide the best quality because colors have been removed.
Other Tips: When shrinking images, resize first and reduce color depth second, for the best anti-aliasing results. Reduce color depth in steps - 256 to 128 to 64 to 32 to 16 - as this will often produce better weighted colors than a jump from 256 to 16. Whichever format you use, be sure to save images at a resolution of 72 dpi, as anything higher is a waste when images are displayed on screen. Only use graphics where you need them. A good designer can produce a clean, attractive and easy-to-navigate site with just a few well-placed image files. Web surfers have a very short attention span, so a fast site is a popular site.
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