Legacy ImageMagick Discussions Archive

Hi,

I want to create a mask image. I want to use an alpha channel as a mask but I don't know how to get an alpha channel from a png image in perl script. I am new in perl and ImageMagick, Can somebody help?

Just extract the alpha channel. look for separate in the perlmagick docs

Separate works, thanks, but I still have a problem when converting this mask to bmp,
I have a png image and I want to have a 8bit grayscale bmp mask and 24bit bmp image, I try this to create the mask
convert image.png -channel matte -negate -separate mask.bmp
output mask.bmp has 1-bit alpha channel, later when I build from this bmp symbian mbm file I get horrible effect. How to remove this 1-bit alpha channel from output bmp image??? I tried to add -type TrueColor
convert image.png -channel matte -negate -separate -type TrueColor mask.bmp
but it didn't change anything, can someone help, it is very important for me now

To remove the alpha from the image use Evaluate to set the alpha mask to opaque. or just turn off the 'matte' channel.

I added +matte option to remove alpha channel from output image:
convert image.png -channel matte -negate -separate +matte -depth 8 mask.bmp
I still get mask.bmp with 1bit alpha channel, its type is Gra yScaleMatte, why?
I also tried to add -type Grayscale to this command but I always get GrayScaleMatte with this 1bit alpha channel.
Can You write me how to remove this alpha channel with -evaluate option?

Sounds to me like the BMP code always adds it. have you tried one of the other BMP formats.
List all formats with In my list I see BMP2 and BMP3 as alturnatives.

This works! Hurra hurra! alpha channel has been removed from mask.bmp,
great great great thanks!