Subject:
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Re: Hangin' around
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Newsgroups:
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lugnet.cad
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Date:
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Tue, 15 Aug 2006 19:06:22 GMT
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Viewed:
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1745 times
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In lugnet.cad, Timothy Gould wrote:
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On the topic of jpegs, if you convert them at high enough quality (I use
-quality 90% setting from IM convert) I think they can actually look better
than lossless images because the compression rounds off some of the harsher
lines in the renders. I switched to using jpegs for all my wallpapers quite a
while ago and keep the png format for any further manipulation.
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In my experience JPEG versions of computer-generated pictures only really look
good when you turn off color sub-sampling during the JPEG compression. Many
(most?) programs that allow you to create JPEG images don’t support this option.
It also doesn’t seem to have a consistent terminology. In Irfanview, check the
“Disable color subsampling” option in the JPEG save options box. In ACDSee, I
think it’s something like 1x1 sampling vs 2x2 sampling.
One of the below images used color subsampling. The other didn’t. Can you tell
which is which? (Note that I created PNG crops of the original JPEG images.)
Notice in particular the red edge lines, and how much more crisp they are in one
of the images. Note that both images were saved with quality set to 90%. The
subsampled original image was 45KB. The other was 57KB. The original PNG was
50KB, but the full original had a lot of white background, and PNG does a much
better job on this than JPEG.
One thing to note is that even though many programs don’t support generating
JPEG files like this, all JPEG viewers should support displaying them.
--Travis
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Message has 2 Replies:
 | | Re: Hangin' around
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| (...) which IMO are so detrimental for all pictures containing high frequencies (=sharp edges). PNG is lossless, and doesn't generate anything like that. I know what I would use... JPEG is (maybe?) good for continous color changes, ie photos. (18 years ago, 15-Aug-06, to lugnet.cad)
| | | Re: Hangin' around
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| (...) Hi Travis, I didn't realise that you could switch off parts of jpeg compression. Very handy to know. I didn't quite spell it out in my previous post but I actually meant for raytraced images rather than general renders. For edge-lined renders (...) (18 years ago, 16-Aug-06, to lugnet.cad, FTX)
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Message is in Reply To:
| | Re: Hangin' around
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| (...) Hi Willy, I didn't realise you were using BMP format. If you don't already have a copy of (URL) ImageMagick convert> I can't recommend getting it enough. It is the most convenient conversion software ever if you use the command line and if (...) (18 years ago, 15-Aug-06, to lugnet.cad, FTX)
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