Hey Bob:
I finally finished some chores and have compared the files I processed, so I can give you a definitive answer on what went on. We'll use the second picture down from where I started as the example.
I started out with a 2,299 KB file and shrunk it down to 40% of its size. Color count before shrinkage was 339,919 colors. The finished file was 144 KB and only had 137,106 in it, as probably 70% to 80% of its pixels were eliminated. therefore, it will naturally have fewer distinct colors in it. Jpegs depend heavily on color indexing for size of the file, and not just its dimensions. As the number of colors increase, so does the color indexing and size of the file, in what seems an exponetial increase (Don't forget that z^(x/y) is still exponential), verses linear. Although the first picture and second picture are the same file size, 144KB, the second is larger, and has less color mapping, number of colors in it.
This site states its limit at 150KB for uploads. However, this is false. It is actually 150,000 bytes. 150KB = 150*1024 bytes, which = 153,600 bytes. This is why I never go over 145KB to post on here, as when I try to get closer to 150KB, it starts failing to upload. Max size is actually 146.48 Kb.
When I 'shrink these pictures, I use an old program called Irfanview. I use the old version, which is much less complicated and gives quick results. I open the original in it, click on View, select Resize/Resample and then Keep Aspect Ratio, and set the new size to 40% to start off with. This way the program reinterpolates the pixels from a fresh loading -> less distortion creeps in. Then tweak the percentage until you get between 144 KB and 146 KB. Easy, quick, and the results are excellent. You can do the same thing in any graphics processor, and get as complicated as you want, messing with size and 'quality (this is usually color depth in most programs)' as you go. I just don't bother.
(Message edited by poor_nigel on April 28, 2005)
