Notes on Chapters 16-18 of Niederst
Portable Network Format (PNG)
Not a JPEG substitute since PNG's lossless compression will nearly always result in larger files than JPEG's lossy compression scheme. A good GIF substitute because PNG's better compression will result in smaller files and a more sophisticated interlacing technique and thus starts displaying the image in 1/8th the time. PNG may be advantageous in certain contexts due to its advanced features such as variable transparency levels and automatic image correction, including gamma and color balance correction.
Designing Graphics with the Web Palette
There are 3 systems for defining RGB values -- decimal, hexadecimal, and percentage. The 6x6x6 color cube values are 0, 20%, 40%, 60%, 80%, and 100%, or 00, 33, 66, 99, CC, and FF.
"The only advantage to converting photographic material to the Web Palette is that you can see exactly how the image will appear on 8 bit displays and you will know that the image looks exactly the same for all users. Saving it as a JPEG will generally result in a smaller file size and will allow any user with a 24-bit display to see it in its original color.
Browsers that do not support GIF animation will display a static image -- the problem is that some browsers display the first frame and some the last frame. Therefore, if possible, make both meaningful.
Can set frame delay, transparency, and disposal methods (upspecified -- complete replacement, do not dispose - pixels not replaced by next frame continue to display, restore to background, restore to previous).
Multiple palettes dramatically increase file size so try to use a global one for the whole animation