RGB 8bits and Alpha 1bits

Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
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glennrp
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Post by glennrp » 2006-04-01T08:19:37-07:00

May I have a copy of your source image? There is no such thing as a 1-bit alpha PNG unless you mean a PNG where the transparency is carried in the tRNS chunk.

Glenn

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glennrp
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Post by glennrp » 2006-04-01T08:21:05-07:00

P.S. you could try -sample instead of -resize.

Glenn

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Post by glennrp » 2006-04-03T07:43:12-07:00

Identify says the alpha is 1-bit even though it's really 8-bit, when the only values are 0 and 255.

The "resize" operation creates other values due to interpolation of alphas.

To get back to the 0/255 condition, use -ordered-dither command (look it up to get the exact syntax; it's something like
"-ordered-dither 2x2 opacity" but I don't remember exactly).

Glenn

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