 sporkmedrop the crantini and move it, sisterPremium,MVM
join:2000-07-01
Morristown, NJ | reply to MxxCon
Re: Our way or the highway said by MxxCon:The problem with such rule is there is no standard measurable unit of image "quality". There certainly good be though. Take the original, zoom in to some number of pixels. Do the same on the compressed version. Count how many pixels are different.
You can do this experiment at home. Take a high quality jpg. Save it with really crappy compression settings. Open up both. Zoom in to a complex area of the image. Count the pixels that are different. |
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EPS
join:2008-02-13
Hingham, MA | But what is "different"? If a shade of red is slightly changed, is that equal to the shade of red getting blurred into gray? |
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 MxxCon
join:1999-11-19
Brooklyn, NY | reply to sporkme
said by sporkme:Take the original, zoom in to some number of pixels. Do the same on the compressed version. Count how many pixels are different. You can do this experiment at home. Take a high quality jpg. Save it with really crappy compression settings. Open up both. Zoom in to a complex area of the image. Count the pixels that are different. that kind of testing goes exactly against the way lossy video and audio compression works.
you try to throw away as much data as possible while trying to keep it perceptually identical TO HUMANS.
so at which point will you consider 2 pixels different? how would you know if some different pixels are important in an image or not?
would you want to waste video bandwidth trying to preserve details of a perfectly black sky with a few pixels being one shade brighter? or would you rather use it somewhere more obvious? |
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 DogfatherPremium
join:2007-12-26
Laguna Hills, CA | That is part of what a standard would determine...at what point are they considered different. |
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