lau wrote:
0_equals_true wrote:
It is called dithering. Gif doesn't have a good compression algorithm, so uses a limited color index as an alternative. If it doesn't have the have the right colour or tone it can use the nearest equivalent or to dither (which is a pointillism). If you turn off dither it will look even worse for that number of colours.
In short don't use gif to save high quality photos.
I don't believe
dither has much to do with it either. GIFs don't generally use that. In fact, it tends to result in pretty gruesome effects, overall, on an image - especially when the pseudo-random algorithm has too long (surprisingly) a period. It can tend to "fudge" the non-dithered artefacts, but does so by blurring the overall image, and also can introduce its own set of artefacts.
The GIF compression is fairly good - when applied to the sort of image it is intended for, which is NOT photographic ones.
Yes, Dithering is what causes the specs in the gif photo, I just think your looking at the term the wrong way, I can give a hundred links if need be
Pretty much where all saying the same thing but not using the wright terms for it. I think every one would agree that the gif drops colors, because of the limited amount of colors it has avaliable, doesnt nessesarly have to be 256, just that amount or under. It filles in the empty pixels by trying to match to the closest color to the adjasent pixel, unfortnantly it doesnt work to well, hence the colors that dont match. There is no blurring of the image, just the aperance of that, because of the droped pixels. Also the reason I said about color profile, (has nothing to do with the specs in the pic) was because the gif uses differnt colors then a jpg (even if close they are still differnt), so you are never going to get a acurite image, you should try to use the same color profile and file format across the whole process of taking the picture, editing it, ect. This could result in droped pixels in the original image we are comparing it to (if a correct profile wasnt followed), and lead to the gif looking even worse, because more colors where changed.
Just because I dont try to sound like a genius by using the scientific for EVERYTHING, doesnt mean I am wrong. I could just care less what algorithm it uses.
Anyway, here are some links about dithering related to gif (not in general term like wiki.)
http://webstyleguide.com/graphics/dither.html
http://www.siriusweb.com/tutorials/gifvsjpg/
http://www.vimas.com/ve_gif.htm