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Full Version: PNG transparency - How can I determine if it's set?
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Al Savage
I have a collection of PNG files. Some were apparently saved with the "Write Transparency Chunk" turned on. Example:


The greenish background bleeds through, which in the case of this particular image, is undesireable.

Is there a method, using PMV, to determine which of several hundred PNGs are in this condition, and if so, is there a batch method to turn transparency off for these images (ie re-save them with that option disabled)?

Al S.
Since PNG is lossless, you can safely do a batch conversion to a different directory for all those files.

Yes, that is a solution to this particular situation (batch converting a few thousand files in order to turn off transparency, and in the process losing the valuable-to-me timestamp for each file), but you haven't answered my question.

How do I use PMV to determine the current state of the transparency?

Al S.
You can't use PMView to determine the current state of the transparency; currently it does not show the flags.

You need a developer's PNG utility that will show you the option flags. (Hint: look for "dumppng" or "pngdump").


Edited By Peter on 1102905885
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