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Discussion Board -> Desktop Wallpaper, Art, etc. -> On-site JPG compression of red

On-site JPG compression of red

kjh000
07/21/05 8:16 AM GMT
I was a bit surprised a while ago to see that images I made in certain hues of red looked terrible here on caedes while they looked good when I viewed my original files at my comp at home. I found out some new stuff about the on-site compression of files here and made the conclusion that I would be better off submitting uncompressed files instead of my usual attempts to not overload the server with files larger then 500k.

That failed too, only showing a small, barely noticeable improvement in how much details was left in the image but still looking like it's run through a heavy blurring filter... The argument offered in the discussion seemed to indicate that it's the jpg-compression itself that is the problem, having a particular problem with red and then in particular small one pixel-with details.

The only problem I have with this is that I compress my files to the approximate same size in my mac with none of that loss of details. Is this just another example of how great Macintosh computers and software are or is the on-site compression settings possibly not fine tuned? I've kept the files here on Caedes for future reference and they still look kind of nice but not at all like I feel they should look. Ok, I'm maybe a bit picky with these things but I feel it somewhat defies the purpose of submitting images here if they are not the same as the ones I produce... I find it hard to believe, even if I don't hole it to be impossible, that it's just because I have such a wonderful piece of hardware to work with. I doubt caedes.net is run on just any tincan and would like to see the same quality here as I can see on my own comp. I don't want people to think I've lost my sight the last couple of monts, submitting unintentionally blurry images...

I've uploaded 1600x1200 copies of three files to another server so you can see the difference for your self (the last one is perhaps not that bad perhaps (probably because of the different hue) but it still shows). (I hope the links work, give me a holler if it doesn't cut it.) So here they are:

Shadow Wars, Caedes version and my "original" version.

Under the Surface, Caedes version and my "original" version.

Crackled Lava Stream, Caedes version and my "original" version.

Ok, here ends of the rant of the day. ^_^

/Klas
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Blague
07/21/05 6:11 PM GMT
As I know nothing about Caedes compression,the only consolation I can give is that you're not going crazy,and it is noticible. Sorry for not being able to help more.
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::CaptainHero
07/21/05 6:18 PM GMT
As far as I understand it, you can't fine tune the site compression - it just runs through some algorithm like any other compression. It's done through ImageMagick and I wouldn't imagine you can calibrate it.

I think that whether you upload it compressed or uncompressed, it will still get subject to the compression process.
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"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell
*caedes
07/22/05 1:33 AM GMT
I thought that I had noticed a slight problem that JPG has with reds as well, and I do see a slight difference between the images that you've posted. I think that in order to get a valid comparison however, we would have to compare images which are the same file size. Obviously, if you compress one image to half the filesize of another the larger file will look better, that's just jpg doing what it is supposed to do. So I guess that the real issue is that you think we should be using less compression on the images here on the site, not that the compression has a defect.

I chose the current compression level because it gave good visual results for most images while keeps file sizes down to a reasonable level. If we decide that we need to use a less lossy compression level then that's fine, we just have to deal with the extra file storage and bandwidth requirements that come with it.
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-caedes
kjh000
07/22/05 7:29 AM GMT
I understand perfectly. I'll do a new comparison with more equal file sizes. I'll have to argue though that it's not compressed to half the size but only a couple of percent from the original file of about 5,5 MB (Shadow Wars only about 2)...

Perhaps this sharpens the argument of offering a special link to the original file. (That you no doubt keep on the server, right?) Especially for those of us that has gone through the trouble of not wanting to burden your server with files larger then 500 k...

I wonder, does it take more server space to keep our uncompressed files (of 5 MB per image) that I felt we were encouraged to submit in that earlier discussion, rather then the 500 k compressed ones I thought was best to submit (to save your bandwidth). Or making your compression a bit less harsh and leaving at least 500 k images (for 1600x1200 copies)
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+tbob
07/22/05 8:08 AM GMT
Does it help if you upload a image you compressed yourself ?Everthing I upload is smaller than 500k.
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kjh000
07/22/05 4:02 PM GMT
Definitely not. That was up for discussion some time ago. Lossy compressions in succession is not good in general and in this particular example is worse then it usually can be.

(I've tried both methods and up until that aforementioned discussion I always kept my images below 500 k or just a tiny bit above it. Now I'm not sure what to do but I didn't see any big difference on the end result here between the on-site compressions of my 500k file and the exact same image in a 5,5MB uncompressed PSD-file...)
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kjh000
07/26/05 5:57 PM GMT
Ok I had some time yesterday to make new files. I did a new compression of the images to a file-size equal or rather, a bit smaller then the ones you can find here on caedes.net (comparing the 1600x1200 size of the image).

Shadow Wars, Caedes version and my new smaller file-size "original" version.

Under the Surface, Caedes version and my new smaller file-size "original" version.

Crackled Lava Stream, Caedes version and my new smaller file-size "original" version.

In all cases except for the last image (that has not got that particular hue of red either) the difference is still quite noticeable. So, what's up with the on-site compression? Or... Is it just because I run superior Macintosh hard- and software? ^_^

Or in other, perhaps less offending words (for the everyday windows user ;P) how can this be? (Not that I intend to be offensive, I'm just too tired atm try and moderate my poor taste of humour. Or what's it called... :D)

This is all a mystery to me. Particularly since I recently saw a recommendation of making submissions smaller then 800k when I in my other discussion considering on-site compression gathered as much that you are not supposed to submit compressed images if you want the quality of your images to be the best possible.
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*caedes
07/26/05 6:35 PM GMT
Yes, I can still see differences. One issue is that the JPG compression algorythm has some parameters that change how the compression is done. I think that you will usually be able to hand-tune those parameters to get better quality for a given file size than you would be able to with an automated system. It appears that the tradeoff that the current software makes is that it blurs out low-contrast images.

I also have an idea of some changes that can be made to the site software that should limit the effects of recompression. Thanks for bringing this up.
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-caedes
kjh000
07/26/05 8:24 PM GMT
Thanks for answering back. :) I appreciate that. I think it's an important (but perhaps not that urgent) issue since I care about the quality of the art we share here on caedes.net. I can't really say I hand-tune my compression. I'm no computer wizard that can tweak odd settings that no one heard of. ^_^ I just run the default settings in GraphicConverter (I checked now and it's set to non-progressive JPEG 6.0 library with no subsampling).

I'm looking forward to seeing what nifty solutions you can come up with in the future.

For the record I'm not thinking this is the most important thing on earth though. ^_^ I just noted it since I've never had any noticeable problems earlier with my submissions. Up until this issue came up I consequently uploaded images that was compressed to a file-size of just about 500k.
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