Mask with input image <256 colors/bug?

[davidfooks]

Hi,

I'm running

Code: Select all

convert input.png -mask mask.png -fill red -draw "rectangle 0,0,512,512" out.png

Which runs fine with input images >256 colors. However, if I try to run an image with <256 colors I always get a transparent background as the output.

All I want to be able to do is convert the source image so that this no longer happens. However, I've tried adding -type TrueColor and -colorspace RGB but neither fix this.

If I output debugging information the only different lines are:

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<<<<<<< Working >256 image
      Reading PNG bKGD chunk.
2013-01-04T16:02:12+00:00 0:00.010 0.000u 6.6.9 Coder convert[11703]: png.c/ReadOnePNGImage/2101/Coder
      raw ping_background=(255,255,255).
2013-01-04T16:02:12+00:00 0:00.010 0.000u 6.6.9 Coder convert[11703]: png.c/ReadOnePNGImage/2125/Coder
      bkgd_scale=257.
2013-01-04T16:02:12+00:00 0:00.010 0.000u 6.6.9 Coder convert[11703]: png.c/ReadOnePNGImage/2128/Coder
      ping_background=(65535,65535,65535).
2013-01-04T16:02:12+00:00 0:00.010 0.000u 6.6.9 Coder convert[11703]: png.c/ReadOnePNGImage/2145/Coder
      image->background_color=(65535,65535,65535).
2013-01-04T16:02:12+00:00 0:00.010 0.000u 6.6.9 Coder convert[11703]: png.c/ReadOnePNGImage/2383/Coder
===============
>>>>>>>>>>Broken <256 Image

...

<<<<<<< Working >256 image
No room in the colormap to add background color
===============
background_color index is 232
>>>>>>>>>>Broken <256 Image

...

<<<<<<< Working >256 image
number_opaque          > 256
===============
number_opaque          = 232
>>>>>>>>>>Broken <256 Image

Any ideas?

[fmw42]

Please post links to your input and mask files, so others can test.

You can try adding PNG8:output and see if that helps.

Or adding -colors 256 and/or -type palette.

Otherwise, the PNG developer will need to check and would need your images.

[davidfooks]

I've tried adding -colors and -type but with no change.

Ok, the command I'm running is:

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convert input1.png -mask mask.png -fill red -draw "rectangle 0,0,256,256" out1.png
convert input2.png -mask mask.png -fill red -draw "rectangle 0,0,256,256" out2.png

With the following files
input1:

input2:

mask:


And the output I get is
out1:

Which doesn't look right

out2:

That's how it should look.

If I add a second color to the input inside of the mask
input3:


and run:

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convert input3.png -mask mask.png -fill red -draw "rectangle 0,0,256,256" out3.png

I get this
out3:

So now its correct!

Note that if the color is outside of the mask then I still get out1.

[davidfooks]

Oh and I'm running Ubuntu 12 with ImageMagick 6.6.9-7 Q16

[snibgo]

I'm not familiar with this style of mask, but putting +mask before the output filename may give the results you want.

[fmw42]

On my IM 6.8.1.9 Q16 Mac OSX Snow Leopard, I get the following:

convert input1.png -mask mask.png -fill red -draw "rectangle 0,0,256,256" out1.png




or if I negate the mask

convert mask.png -negate mask2.png
convert input1.png -mask mask2.png -fill red -draw "rectangle 0,0,256,256" out1b.png




So I suspect it is your older version of IM that needs an upgrade.

[davidfooks]

Ok I'll try updating.

The images you show there are still incorrect. It should look like out2 or out3, a red circle around the original image.

[davidfooks]

Nope updating didn't help just get the same output running ImageMagick 6.8.1-9 2013-01-08 Q16

[snibgo]

Have you tried my "+mask" suggestion? I think it gives the result you want (in v6.7.9).

[fmw42]

Ok I'll try updating.

The images you show there are still incorrect. It should look like out2 or out3, a red circle around the original image.

I think your mask circle is larger than the circle in the images, so it will also keep some of the background white.

[davidfooks]

Ok I'll try updating.

The images you show there are still incorrect. It should look like out2 or out3, a red circle around the original image.

I think your mask circle is larger than the circle in the images, so it will also keep some of the background white.

Yup, its supposed to do that. out1 should look like out3 but without the blue circle.

Thanks snibgo. I needed to add +mask at the end. The docs for this are terrible. The correct operation is:

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convert input1.png -mask mask.png -fill red -draw "rectangle 0,0,256,256" +mask out1.png

Does anybody you know why I need to do this +mask? Or why convert doesn't force you to specify it by throwing a warning

[snibgo]

As I said, I'm not familiar with this method of masking, but it seems to me that "-mask" remains in effect until "+mask", and that the effect of "-mask" is more than just preventing updates to pixels.