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Advice on oddly-coloured images

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Advice on oddly-coloured images Christopher Dawkins 29 May 08:40
  Advice on oddly-coloured images Ofnuts 29 May 09:58
   Advice on oddly-coloured images Christopher Dawkins 29 May 13:26
    Advice on oddly-coloured images Christopher Dawkins 30 May 08:02
Advice on oddly-coloured images Jernej Simončič 29 May 13:30
Christopher Dawkins
2011-05-29 08:40:14 UTC (over 13 years ago)

Advice on oddly-coloured images

Please excuse a non-GIMP query, but I have been a GIMP user (an inexpert one) since the last century and this is the only graphics-related list I am on.

My query is on http://archives.felsted.org/pdfprob/

The problem is that images obtained from a Quark pdf with pdf2html appear in silly (approximately negative) colours, and I need a scriptable method to restore them.

Ofnuts
2011-05-29 09:58:03 UTC (over 13 years ago)

Advice on oddly-coloured images

On 05/29/2011 10:40 AM, Christopher Dawkins wrote:

Please excuse a non-GIMP query, but I have been a GIMP user (an inexpert one) since the last century and this is the only graphics-related list I am on.

My query is on http://archives.felsted.org/pdfprob/

The problem is that images obtained from a Quark pdf with pdf2html appear in silly (approximately negative) colours, and I need a scriptable method to restore them.

Couldn't that be a problem of CYMKRGB mixup by pdf2html?

Or the images from pdf2html are actually JPEG in CYMK mode, and that mode is overlooked by the software you use to view the results, in which case you would just need a utility to convert CYMK JPEG to RGB (ImageMagick will likely do it).

Christopher Dawkins
2011-05-29 13:26:17 UTC (over 13 years ago)

Advice on oddly-coloured images

My query is on http://archives.felsted.org/pdfprob/

Couldn't that be a problem of CYMKRGB mixup by pdf2html?

Or the images from pdf2html are actually JPEG in CYMK mode, and that mode is overlooked by the software you use to view the results, in which case you would just need a utility to convert CYMK JPEG to RGB (ImageMagick will likely do it).

Bingo! Bang on the nail! Very many thanks for this diagnosis. Just found and tried the 'identify -v ' command and it reports 'Colorspace CMYK'.

More difficult, at the moment, is to convert it. All variations on -colorspace fail to have any effect (on IM 6.6.3-10), and -profile appears to be unrecognised. On GIMP there is a 'Rearrange colormap' but it's greyed out: presumably the jpg has no colormap.

I'll plough on through Google (I have only FreeBSD and Ubuntu machines).

Jernej Simončič
2011-05-29 13:30:36 UTC (over 13 years ago)

Advice on oddly-coloured images

On Sun, 29 May 2011 14:26:17 +0100 (BST), Christopher Dawkins wrote:

More difficult, at the moment, is to convert it. All variations on -colorspace fail to have any effect (on IM 6.6.3-10), and -profile appears to be unrecognised. On GIMP there is a 'Rearrange colormap' but it's greyed out: presumably the jpg has no colormap.

If you open and save with GIMP, it should be enough, since GIMP doesn't support CMYK.

Christopher Dawkins
2011-05-30 08:02:38 UTC (over 13 years ago)

Advice on oddly-coloured images

*** PROBLEM SOLVED in 24 hours:

The problem was that jpeg images generated from Quark by pdf2html were in silly colours.

My query is on http://archives.felsted.org/pdfprob/

Couldn't that be a problem of CYMKRGB mixup by pdf2html?

More difficult, at the moment, is to convert it. All variations on -colorspace fail to have any effect (on IM 6.6.3-10), and -profile appears to be unrecognised. On GIMP there is a 'Rearrange colormap' but it's greyed out: presumably the jpg has no colormap.

I posted this on an ImageMagick forum. The answer was that the images needed TWO transformations. They were (1) CMYK and (2) negatives. So the required command (two alternatives out of dozens of possibilities) was

convert -colorspace RGB -negate index-1_8.jpg RGB.jpg or
convert index-1_8.jpg -negate -profile USWebCoatedSWOP.icc \ -profile sRGBSpac.icm RGB2.jpg

I apologise for creating noise on this forum for a non-GIMP problem, but many thanks to Ofnuts for helping me on my way.