Color degredation

Kaji01 · Post by **Kaji01** » Wed Nov 05, 2003 3:34 pm

Just a little something I've noticed when working with still images is that, for example, when I'm working with it in Paint and then save it and reopen it immediately the colors seem to shift and degrade, often creating seemingly random patches of similar but distinguishably different colors in the file that had just had solid colors not 5 seconds before. I've also seen this quite a bit in a number of videos I've downloaded (as well as those I've created), although in such cases the patches shift form from frame to frame, regardless of any actual motion. I was just wondering if there was any particular technical term for this and if people knew what the best methods are for preventing it in both still images and animated clips...

Anime2Envy · Post by **Anime2Envy** » Wed Nov 05, 2003 3:45 pm

Sounds like normal compression to me. When you compress say a picture to a jpeg information is always lost, but you get a smaller file size. The same holds true for converting a video to a non-lossless codec, such as divx. Use could use lossless formats such as .tiff for stills or HuffYUV for video, but the file sizes are MUCH larger.

godix · Post by **godix** » Wed Nov 05, 2003 4:01 pm

I'd say this was a compression artifact but AFAIK MS Paint can only do .bmp which is lossless. If it's not compression artifacts then the most next most likely answer is that you saved a picture in 256 colors while the original pic had more.

DJ_Izumi · Post by **DJ_Izumi** » Wed Nov 05, 2003 5:18 pm

MSPaint can save in various formats, including GIF, Jpeg (Speaking of lossy?), Tif and various levels of Bitmap.

He's either saving it to say, 8bit color, or Jpeg.

I've seen a few AMVs that are encoded at 8bit... For some reason. Yummy, Indeo, Microsoft Video 1 and Cenepak AMVs. :X

Kaji01 · Post by **Kaji01** » Wed Nov 05, 2003 8:02 pm

Ah, never realized JPEGs were so lossy...Still, I guess it would go to explain why I've always heard that JPEGs are better suited to detailed things such as photos and GIFs are better suited to drawings and such...

godix · Post by **godix** » Wed Nov 05, 2003 8:15 pm

Odd, my version of MSPaint can only do a few different levels of .bmp. Of course I'm only running 2K so they must have changed it for XP.

DJ_Izumi · Post by **DJ_Izumi** » Wed Nov 05, 2003 8:23 pm

Jpegs can be very lossy, or it can be very good (for image distribution only that is). Jpeg is SUPPOSED to have a slider for quality, however certian programs will not utalize this option and do only a medicore job at compression.

Anime2Envy · Post by **Anime2Envy** » Thu Nov 06, 2003 3:51 pm

Odd, my version of MSPaint can only do a few different levels of .bmp. Of course I'm only running 2K so they must have changed it for XP.

This is something that I have been trying to figure out for a long time. Ever since win95 I have been able to open jpegs with paint, but the ability to save them as jpegs varies by windows installation. I have used many machines running the same version of windows, some will let you save as jpegs, and some won’t. Must be a Microsoft thing.

danielwang · Post by **danielwang** » Fri Nov 07, 2003 12:39 am

Sounds normal.

Please remember that the JPEG features of Paint have been recently introduced, they wre not present on 95/98/ME, etc. Any version of Paint with XP should work.

Paint does not use an adjustable or dynamic compression quality, it is set at 35%. However, if you do not close the program, it keeps it in a lossless format until you save - therefore, the loss does not become apparent until you open it again.