Legacy ImageMagick Discussions Archive

Thanks for the info. Looks like it'll be easier to write a standalone tool for this!

I want to take an RGBA png input, extract the G & B channels, and pack them into a single 8-bit grayscale image. In other words the final 8-bit grayscale PNG output has the source Green channel packed into the lower 4 bits, the Blue channel packed into the upper 4 bits. I can see how to extract the ...

YES! That's nailed it.

Thanks very much!

First we handle the multiply, then we use Copy_Opacity to add the alpha channel back in. Copy_Opacity copies the alpha channel if there is one, but otherwise it uses the image itself, grayscaled, as the alpha channel. Instead of copying the alpha back into the original image, we could copy the ...

Sorry to resurrect this but if I run the command on an image without an alpha channel it gets screwed up (if it's 24 bit it seems to get alpha'd by maybe 50%, if it's 8-bit paletised it went super bright and also very alpha'd). Is it possible to change the command line to handle this case and not do ...

Fantastic! The last command line lets me chain additional options and works great.

Your help is much appreciated!

Thanks both of you - I appreciate avoiding the -size option! If I wanted to do some other operation, and as a final step do this, how would I set that up. For instance (note resize is not always happening so I may not know the size up front): convert in.png -resize 128x128! -blur 1 [now apply the ...

I've been struggling trying to figure out a command line which will let me to create premultiplied alpha images out of my PNGs, can someone help me out please? The process I'm after is: Take input image (PNG) Multiply each pixel color value by the pixel alpha value Output PNG with the modified ...