Legacy ImageMagick Discussions Archive

Using 6.8.6.10 and 6.8.7.0 the following combine command is displaying a grayscale image with JPG. It works fine under 6.8.6.9 or with PNG. Mac OSX Snow Leopard

convert rose: -separate rose_%d.jpg

# this fails
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine show:
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine 1tmp1.jpg
convert 1tmp1.jpg show:

# this fails
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine show:
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine 1tmp1.png
convert 1tmp1.png show:


convert rose: -separate rose_%d.png

# this works
convert rose_0.png rose_1.png rose_2.png -combine show:
convert rose_0.png rose_1.png rose_2.png -combine 1tmp1.png
convert 1tmp1.png show:

Adding -colorspace sRGB after the -combine, does not help Tested again with IM 6.8.7.0

These still fails:
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine -colorspace sRGB show:
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine -set colorspace sRGB show:


However, these works:
convert rose_0.jpg rose_1.jpg rose_2.jpg -set colorspace sRGB -combine show:
convert rose_0.jpg rose_1.jpg rose_2.jpg -colorspace sRGB -combine show:


Magick: Is this a bug or a new requirement/feature?

This is a bug and will be fixed in 6.8.7.1

dlemstra wrote:This is a bug and will be fixed in 6.8.7.1

Thanks for the reply Dirk.

Do you know if this is related to my other bug report with -separate at viewtopic.php?f=3&t=24188

Fred

It doesn't look like this is related, I will look into the other bug to see what is happening there.

Here are some examples that seem to show that it might be format related. PNG works, but miff and jpg do not.



This seems to work fine:
convert rose: -separate rose_%d.png
convert rose_0.png rose_1.png rose_2.png -combine newrose.png
display newrose.png

But this comes out grayscale in jpg format:
convert rose: -separate rose_%d.jpg
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine newrose.jpg
display newrose.jpg

But this comes out grayscale in miff format:
convert rose: -separate rose_%d.miff
convert rose_0.miff rose_1.miff rose_2.miff -combine newrose.miff
display newrose.miff

Further problems with -combine


Create test sRGB black image and convert to CMYK to see if that works and what the values are in CMYK

convert xc:black xc:black xc:black -combine -colorspace CMYK txt:
# ImageMagick pixel enumeration: 1,1,65535,cmyk
0,0: (0%,0%,0%,100%) #000000000000FFFF cmyk(0,0,0,255)

So the above is fine.


So take the cmyk values and create the reverse

convert xc:black xc:black xc:black xc:white -set colorspace CMYK -combine -colorspace sRGB txt:
Abort trap



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: (99.990844586861982179%,99.990844586861982179%,99.990844586861982179%) #FFF9FFF9FFF9 srgb(99.990844586861982179%,99.990844586861982179%,99.990844586861982179%)

which comes out as nearly white.

We can reproduce the problem you posted and have a patch in ImageMagick 6.8.7-1 Beta available by sometime tomorrow. You'll also need this command:

magick wrote:We can reproduce the problem you posted and have a patch in ImageMagick 6.8.7-1 Beta available by sometime tomorrow. You'll also need this command:

Code: Select all

convert xc:black -colorspace CMYK \
  xc:white -set colorspace CMYK -compose CopyCyan -composite \
  xc:white -set colorspace CMYK -compose CopyMagenta -composite \
  xc:white -set colorspace CMYK -compose CopyYellow -composite \
  xc:black -set colorspace CMYK -compose CopyBlack -composite \
  -colorspace sRGB txt:

Why is -set colorspace needed? Is should not be needed since the first line sets the colorspace to CMYK. This is per Anthony's examples at http://www.imagemagick.org/Usage/color_ ... bine_other

And what about the more current approach that aborts


convert xc:black xc:black xc:black xc:white -set colorspace CMYK -combine -colorspace sRGB txt:
Abort trap

Does it abort with the latest ImageMagick 6.8.7-1 Beta?

magick wrote:Does it abort with the latest ImageMagick 6.8.7-1 Beta?

No, that is fine. Thanks.

imbh convert xc:black xc:black xc:black xc:white -set colorspace CMYK -combine -colorspace sRGB txt:
# ImageMagick pixel enumeration: 1,1,65535,srgb
0,0: (0%,0%,0%) #000000000000 black


But this still does not work without -set colorspace CMYK before each -channel (which does work) and I do not understand why that is needed now, when it was not before as per http://www.imagemagick.org/Usage/color_ ... bine_other


imbh 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

As for fmw42, on Windows 7, the command ... ... crashed under v6.8.7-0 but succeeds under 6.8.7-1beta, returning the expected result "0,0: (0%,0%,0%) #000000000000 black". Thanks.

snibgo wrote:As for fmw42, on Windows 7, the command ...

Code: Select all

convert xc:black xc:black xc:black xc:white -set colorspace CMYK -combine -colorspace sRGB txt:

... crashed under v6.8.7-0 but succeeds under 6.8.7-1beta, returning the expected result "0,0: (0%,0%,0%) #000000000000 black". Thanks.

Yes, it does the same for me on my Mac (unix)

fmw42 wrote:Here are some examples that seem to show that it might be format related. PNG works, but miff and jpg do not.



This seems to work fine:
convert rose: -separate rose_%d.png
convert rose_0.png rose_1.png rose_2.png -combine newrose.png
display newrose.png

But this comes out grayscale in jpg format:
convert rose: -separate rose_%d.jpg
convert rose_0.jpg rose_1.jpg rose_2.jpg -combine newrose.jpg
display newrose.jpg

But this comes out grayscale in miff format:
convert rose: -separate rose_%d.miff
convert rose_0.miff rose_1.miff rose_2.miff -combine newrose.miff
display newrose.miff

The above issues all seem to work correctly now in IM 6.8.7.1 beta

The only remaining issue here is why -set colorspace needs to be added to each line of

imbh 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:

This was not needed before as per http://www.imagemagick.org/Usage/color_ ... bine_other

Why is this now needed?

As it currently stands sometimes -combine needs -set colorspace before. sometimes it needs -set colorspace afterwards. The before case is especially important for the black channel of CMYK, as most colorspaces do not have the 4th channel for -combine to copy the black values into.

But it does NEED a colorspace setting at some point, as it is MISSING information, especially if input images are single channel 'greyscale' images (which is what they should be).

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 -separate and -combine should only copy values as they are it should not modify the values, only separate and merge the color channels.