[Lazarus] PNG vs. JPG

[Pew (piffle.the.cat)]

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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