Legacy ImageMagick Discussions Archive

I wondered if there was come format specification that I needed (e.g. PNG32). RGB_IMAGE.png is 24-bit color, no alpha GRAY_MASK.png is 8-bit grayscle, no alpha RESULT.png should be 24-bit color, 8-bit alpha (32-bit) IM v6.6.3 gives the correct result with both command lines you listed. with v6.8.1-9 ...

The current version ImageMagick-6.8.1-9-Q16-x86-dll.exe also does it incorrectly: 8-bit color + 1 bit alpha. ImageMagick-6.6.3-1-Q16-windows-dll.exe does what it is supposed to do: 24-bit color + 8 bit alpha. The command line is: convert rgb_image.png -alpha set gray_mask.png -alpha off -compose ...

I'm using v6.8.0-5 on Win XP SP3. I'll try updating IM, but it's fairly current.

That still gives me an 8-bit image with 1-bit alpha:



You have to zoom in to the edge of the circle, but both RESULT.png and desired_result.png have 8-bit transparency.

Thanks for your reply I think -alpha copy is extracting the alpha from GRAY_MASK.png? When I used -alpha extract I got 1-bit alpha. This started from a command string that I found in another forum. As I say, my understanding is rather murky. A simple example of the files is: convert RGB_IMAGE.png ...

Hello, I use ImageMagick a fair bit, but usually I have to stumble around until I happen to find something that works. I am trying to use 8-bit grayscale images to apply an 8-bit alpha mask to 24-bit RGB images. After a lot of searching, the best I've managed is: convert RGB_IMAGE.png -alpha copy ...