Image shade changes while converting a tiff to jpg with RGB colorspace

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rajivrp
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Image shade changes while converting a tiff to jpg with RGB colorspace

Post by rajivrp » 2018-06-11T08:08:00-07:00

Hi,

When I convert attached tiff file to jpg mentioning color-space as RGB, its shade changes from brownish to greenish. It produces expected output when we don't pass color-space or keep it 'CMYK', source file is of CMYK type but I am looking for an RGB output.

Command :

convert.exe "Sample.tif" "Output_Default.jpg"
convert.exe "Sample.tif" -colorspace RGB "Output_RGB.jpg"
convert.exe "Sample.tif" -colorspace CMYK "Output_CMYK.jpg"

ImageMagick version: I am using 6.9.2.6 (but it's reproducible with latest version 6.9.9-50 as well)
Environment (Operating system, version and so on): Windows 7, Windows Server 2012

https://drive.google.com/open?id=1fpWkC ... YqAMCtZuLF

Thanks

snibgo
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Re: Image shade changes while converting a tiff to jpg with RGB colorspace

Post by snibgo » 2018-06-11T09:44:47-07:00

"RGB" means linear RGB. I guess you really want "sRGB" (which is non-linear).
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rajivrp
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Re: Image shade changes while converting a tiff to jpg with RGB colorspace

Post by rajivrp » 2018-06-11T11:09:27-07:00

Thanks @snibgo for reply ... but sRGB is producing same output as RGB for this file.

I understand RGB is linear but technically don't you think it's a bug ? Even though source file is CMYK isn't ImageMagick supposed to retain original colors while converting it to JPG with RGB colorspace ? I thought that was a valid expectation, and here there is a big difference in the shade, it's not even close.

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fmw42
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Re: Image shade changes while converting a tiff to jpg with RGB colorspace

Post by fmw42 » 2018-06-11T11:15:27-07:00

-colorspace sRGB works fine for me with your image on IM 6.9.9.50 Q16 Mac OSX. The result is quite different from -colorspace RGB.

Nevertheless, you would get better results converting using profiles.

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