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We are converting group 4 TIFF images to PNG; this may deteriorate the quality.

Is there any way to automate image quality verification using ImageMagick?

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What do you mean by "validation of image quality check"? Verifying if a image is 'of good quality' (for a specific purpose) or not can be a very complex image processing problem. – Renan Apr 4 '12 at 16:11
Isn't PNG supposed to be lossless? So, other than the image size, the quality should not go worse? For JPG, see How to find the JPG quality? Maybe it can do the same for PNG. – Arjan Apr 4 '12 at 16:47
@Arjan being that PNG files are lossless, the idea of 'quality' doesn't exist. – Renan Apr 4 '12 at 17:12
I think so too, @Renan, but just to be sure: I was referring to image dimensions (number of pixels) when referring to "size". (But I admit I was not very clear in that respect.) – Arjan Apr 4 '12 at 17:28
@Arjan I get your point. – Renan Apr 4 '12 at 17:29

As said in a comment, PNG files are lossless, so you can't talk about a "loss of quality".

The closest that PNG has to a "quality" is the compression level, which relates only to file size (a trade-off between file size and time needed to decode the image), not to image quality.

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PNG does support 8 bit in which case one would have dithering or color approximation, banding etc. So long as the OP chooses PNG-24, this isn't an issue. (or rather, so long as the color pallette is not altered) – horatio Apr 4 '12 at 17:59

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