Legacy ImageMagick Discussions Archive

anthony wrote:I have said many times. -combine really needs a 'colorspace' argument. The only solution I can see for backward compatibility is to have a new option that does the same job but takes a colorspace argument.

Remember -seperate and -combine should only copy values as they are it should not modify the values.

The issue is not -colorspace before -combine, but why the need for -set colorspace before -combine when doing it the old way. I was under the impression that the first line

convert xc:black -colorspace CMYK

told IM that the colorspace is CMYK. So why do we need to put -set colorspace before each -copy. It should already know to treat them as CMYK from the first line.

That is true.

In the newly release 6.8.7.1, neither of these reproduce the original black pixel value.



imh convert xc:black -colorspace CMYK \
xc:black -compose CopyCyan -composite \
xc:black -compose CopyMagenta -composite \
xc:black -compose CopyYellow -composite \
xc:white -compose CopyBlack -composite \
-colorspace sRGB txt:
# ImageMagick pixel enumeration: 1,1,65535,srgb
0,0: (100%,100%,100%) #FFFFFFFFFFFF white


imh convert xc:black -colorspace CMYK \
xc:black -set colorspace CMYK -compose CopyCyan -composite \
xc:black -set colorspace CMYK -compose CopyMagenta -composite \
xc:black -set colorspace CMYK -compose CopyYellow -composite \
xc:white -set colorspace CMYK -compose CopyBlack -composite \
-colorspace sRGB txt:
# ImageMagick pixel enumeration: 1,1,65535,srgb
0,0: (100%,100%,100%) #FFFFFFFFFFFF white


The result should be black in either case.

One of the real problems is the CopyBlack does not copy from a grayscale image when no black channel exists!

That is it does not behave as CopyOpacity does, and use grayscale (or the intensity setting from non-greyscale) when the channel being copied does not actually exist.

It is a request I have made quite a few times.

IM 6.8.7-1 Q16 doesn't work very well for me. I get almost white:

• # ImageMagick pixel enumeration: 1,1,65535,srgb
  0,0: (99.925230792706187799%,99.925230792706187799%,99.925230792706187799%) #FFCEFFCEFFCE srgb(99.925230792706187799%,99.925230792706187799%,99.925230792706187799%)

If I add -size 1x1 at the beginning of the commandline I get precisely white:

• # ImageMagick pixel enumeration: 1,1,65535,srgb
  0,0: (100%,100%,100%) #FFFFFFFFFFFF white

If it is supposed to be black as Fred says, that's one bug.
The dependence on -size 1x1 seems to be a second bug.