change of colors while convert

[ebel]

Hi all,
I have a color problem while adding a frame left and right to a picture. How can I avoid that the color changes?

Here is what I have done:
I try to add a 39 pixel frame left and right of my image with ...

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convert 00001.tif -bordercolor Black -frame 39x0 00001_changed.tif

but it changes the colors with a green tint.
I checked the properties of my images with ...

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identify -verbose 00001.tif > 00001.info;identify -verbose 00001_changed.tif > 00001_changed.info; 

I compared the differences with ...

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diff 00001.info 00001_changed.info

and thing the problem is here

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< tiff:photometric: YCBCR
< tiff:rows-per-strip: 2
---
> tiff:photometric: RGB
> tiff:rows-per-strip: 1

Here the complete output of diff

1c1
< Image: 00001.tif
---
> Image: 00001_changed.tif
4c4
< Geometry: 1920x1080+0+0
---
> Geometry: 1998x1080+0+0
6c6
< Print size: 26.6667x15
---
> Print size: 27.75x15
21,24c21,24
< mean: 85.1507 (0.333924)
< standard deviation: 56.0816 (0.219928)
< kurtosis: -1.42352
< skewness: 0.088851
---
> mean: 89.2049 (0.349823)
> standard deviation: 58.5402 (0.229569)
> kurtosis: -1.38967
> skewness: 0.0849196
28,31c28,31
< mean: 79.9954 (0.313707)
< standard deviation: 56.0601 (0.219843)
< kurtosis: -1.36442
< skewness: 0.222793
---
> mean: 84.2508 (0.330395)
> standard deviation: 58.871 (0.230867)
> kurtosis: -1.34246
> skewness: 0.215455
35,38c35,38
< mean: 78.7228 (0.308717)
< standard deviation: 56.224 (0.220486)
< kurtosis: -1.36715
< skewness: 0.251497
---
> mean: 83.0279 (0.3256)
> standard deviation: 59.1097 (0.231803)
> kurtosis: -1.34518
> skewness: 0.2426
43,46c43,46
< mean: 81.2896 (0.318783)
< standard deviation: 56.122 (0.220086)
< kurtosis: -1.38436
< skewness: 0.187721
---
> mean: 85.4945 (0.335273)
> standard deviation: 58.8408 (0.230748)
> kurtosis: -1.35917
> skewness: 0.180792
54c54
< Page geometry: 1920x1080+0+0
---
> Page geometry: 1998x1080+0+0
60,62c60,63
< date:create: 2013-03-16T10:39:44+01:00
< date:modify: 2013-03-15T20:25:39+01:00
< signature: b15ed54e476cc5cc820a70f8adfa9059740bfa44b6a12e83617472442cd08fe8
---
> date:create: 2013-03-16T11:47:48+01:00
> date:modify: 2013-03-16T11:47:48+01:00
> signature: a903bcd357b34c1c8f36b62f803eee18901873318eff0580609cf9c373d66dfb
> tiff:document: 00001_changed.tif
64,65c65,66
< tiff:photometric: YCBCR
< tiff:rows-per-strip: 2
---
> tiff:photometric: RGB
> tiff:rows-per-strip: 1
70,74c71,75
< Filesize: 2.916MBB
< Number pixels: 2.074MB
< Pixels per second: 51.84MB
< User time: 0.030u
< Elapsed time: 0:01.039
---
> Filesize: 5.845MBB
> Number pixels: 2.158MB
> Pixels per second: 215.8MB
> User time: 0.010u
> Elapsed time: 0:01.009

[snibgo]

As you've noticed, the input image is in YCC colorspace, which is quite unusual. Perhaps IM isn't converting it properly, and needs to be told how to do it. Try:

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convert 00001.tif -set colorspace YCC -colorspace sRGB 00001_srgb.tif

"-set colorspace YCC" tells IM the image is in YCC colorspace.
"-colorspace sRGB" converts it to sRGB.
If this doesn't work, can you put 00001.tif somewhere, and post the URL here?

However, my experiments with colorspaces suggest that YCC has a problem; it isn't reversible. Given an image in.png, in sRGB space, the command ...

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convert in.png -colorspace YCC -colorspace sRGB out.png

... should make no change, but it does. out.png is darker than in.png. I don't know if this is an IM bug, or a "feature" of YCC.

[fmw42]

However, my experiments with colorspaces suggest that YCC has a problem; it isn't reversible. Given an image in.png, in sRGB space, the command ...
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convert in.png -colorspace YCC -colorspace sRGB out.png

... should make no change, but it does. out.png is darker than in.png. I don't know if this is an IM bug, or a "feature" of YCC.

Closest I can come is

convert logo: -set colorspace RGB -colorspace YCC -colorspace RGB -colorspace sRGB show:

But the white background is gray. Perhaps this should be reported as a potential bug or a request for clarification on the correct way to do the round trip.

Oddly, I get the same result doing it this way:

convert logo: -set colorspace RGB -colorspace YCC -separate +channel -set colorspace YCC -combine -colorspace sRGB show: