I saved a color cartoon I edited in *.gif and *.bmp and they both viewed much better when I saved it that format versus a jpeg file.
I know that *.jpegs work great for photos but I wonder why they don't work so great for cartoons, color graphics, and similar. Given that jpegs are a lossly format, there must be something about a color cartoon for example that doesn't work very well with jpeg.
Can anyone enlighten me on the 'Why and Hows' of this? TIA.
#1. "RE: Image formats" In response to _Chewy_ (Reply # 0) Fri Jul-30-04 09:08 PM by emes
One thing to consider is the degree of compression (quality) chosen when using jpg. As I understand it the gif format = 'blocks' of color (no shading possible) and very little data information present, whereas bitmap, tiff and jpg etc will give 'shades'. Bitmap and tiff contain much more information than jpg, which even at 'full' quality contains only about half the information of a tiff or 'bitmap'. With jpg it is always a matter of how much degradation of image quality you can accept.
I am interested in the result of saving a gif as a jpg, because I would assume 'graphically' the gif is not further compressible, so what exactly is a jpg doing to it that is causing degradation?
#2. "RE: Image formats" In response to emes (Reply # 1) Fri Jul-30-04 09:15 PM by _Chewy_
> so what exactly is a jpg doing to it that is >causing degradation?
When i saved the cartoon as a jpeg, there were noticeable blotchy areas throughout the drawing. when I saved it as a *.gif or *.bmp, it was hardly noticeable - barely existent.
That was going to be my next question. When saving (or re-saving) in IrfanView or Paint Shop Pro, I make certain that I enable 100% image quality - or zero compression - so theoretically that means no loss. Your symptoms suggest pretty severe compression.
PC specs viewable here... Folding@Home with Team PleasureDome!
#5. "RE: Image formats" In response to Mojo2000 (Reply # 4) Sat Jul-31-04 01:23 AM by emes
Mojo2ooo
While on the topic of jpg compression, what do you know about jpg compression 'increasing' with every 'save'? So that after a few saves, the image is considerably degraded! irrespective of 'high quality' (zero compression) saves. Is there a workaround.
"100% image quality - or zero compression - so theoretically that means no loss"
I don't know that those terms are going to be synonymous.
If you are using a lossy file format, no matter what quality level you set it for, your saved image will be different from the original. That's the nature of the beast.
#7. "RE: Image formats" In response to therube (Reply # 6) Sat Jul-31-04 07:38 AM by emes
So the only way out is to minimize the jpg saves.
For what I am doing (360 degree scrollable images for web), I have been shooting in jpg = strike 1. (I now see that the highest quality available of jpg 'which I have been using' on my camera is only 1/4 tiff. whereas I had thought it was shooting at 1/2 tiff !) I then do the stitching / save = strike 2, then edit in PS and save for web = strike 3. Which explains why I'm having such a problem with final image quality! I should mention that these jpg 1 & 2 'saves' are at zero compression, with the last one for web compressed to the display file size criteria.
I still don't understand why multiple saves in jpg @ zero compression should equate to cumulative degradation? *If anyone can explain this to me, I will be most interested.
The finished work does have to be jpg and not more than 100 kb max, which of course gives me considerable restraints. I have just checked - my stitching software will operate and save in tiff. So I can shoot, stitch and edit in tiff and only step down once for the final publish to web ex PS. The additional photo shoot image load time wont matter as they are all tripod mounted shots, although I will be changing flash cards 4 times more frequently. I will give it a go on my next shoot, expecting to end up with the sort of quality that Iv been trying to get for a long time.
#11. "RE: Image formats" In response to _Chewy_ (Reply # 9) Sat Jul-31-04 08:15 PM by emes
Chewy
The link material in #8 under JPG gives a lot of reasons why you are seeing such degradation.
It would be interesting for you to test the same master by saving as a high Quality jpg, using 'other or various software' to perform the compression. According to the link, you will see variations in quality.
My own question has been answered in as much as a jpg is continuously 'lossy' and 'subject to further degradation each time it is saved', because you are necessarily performing further compression each time you 'save as jpg' whether you want to or not! and regardless of 'full quality', and that is some thing I have failed to allow for.
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