On 01/04/2011 12:46 AM, Jürgen Hestermann wrote:
Bo Berglund schrieb:
PNG is non-loss and also compresses the data much better (for a typical
screenshot) so the resulting file is smaller too...
Why should a loss-less compression compress better than a a lossy
compression?
In general this is not true, just the opposite. But you are right that
for screenshots
PNG is much better because it was optimized for computer generated
pictures
(like screenshots). JPG was made for photos and reduces their size
dramatically
because it takes into account human picture recognition. If you have
photos (made by
a camera) you will always get the best results with JPG.
The problem with jpg is when people start to edit then re-save them.
Have a look on google images for joke images where someone has added a
border and some text to the image. Often times you'll see an bit of
fussy-error area at some point. This is the lossy-ness being introduced
by opening then re-saving, opening the new image and re-saving again 2-3
times or more.
I am not sure whether browsers like Firefox also have lossy-ness when
you find an image and right-click then do a save image as... I think so,
but maybe not, as it probably really only copies the image from the
browser's cache to the new location, hence not really saving but
actually copying.
I always prefer to use png image as masters for editing then output
final image as jpg or png. As this is a duplication problem and also for
the re-saving errors, I tend to only keep png's.
pew
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