Legacy ImageMagick Discussions Archive

The color space of a picture is Grayscale, the file name is gray.jpg
Use convert.exe-type truecolor to convert RGB color space from Grayscale.
convert gray.jpg -type truecolor gray-rgb.jpg

However, I now need to use the ImageMagick API to complete the conversion:

Code: Select all

MagickWand * mw = NewMagickWand ();                
MagickReadImage (mw, "gray.jpg");
                
MagickSetImageType (mw, TrueColorType);
MagickSetImageColorspace (mw, sRGBColorspace);

MagickSetImageFormat(mw, "JPEG");
MagickWriteImage (mw, "gray-rgb.jpg")

The color space of the newly generated gray-rgb.jpg remains the same, still Grayscale.

google the relevant information, find the same problem, but did not find the answer:
https://www.imagemagick.org/discourse-s ... php?t=6888

Which ImageMagick API to use to force Grayscale to convert RGB?

Thank you

In command line:

-define colorspace:auto-grayscale=on|off

prevent automatic conversion to grayscale inside coders that support grayscale. This should be accompanied by -type truecolor. PNG and TIF do not need this define. With PNG, just use PNG24:image. With TIF, just use -type truecolor. JPG and PSD will need this define.

Sorry I do not know the API equivalent. You must also have 6.9.2-0 or higher for that define.

I use im6.8.9

If it is png format pictures:
MagickSetOption(mw, "png:color-type", "6"); //ok to RGB

but, jpg format pictures:
MagickSetOption(mw, "colorspace:auto-grayscale", "off"); //No effect

Code: Select all

MagickSetImageProperty (magick_wand, "colorspace:auto-grayscale", "off");

Thank you very much for yours reply

MagickSetOption(mw, "colorspace:auto-grayscale", "off"); //No effect
MagickSetImageProperty (magick_wand, "colorspace:auto-grayscale", "off"); //No effect

Is my im version too low?

After upgrading to the new version, I found a lot of code needs to be modified, so 6.8.9 has been used.

I'm using 6.9.3-7. That define was introduced for exactly the problem you have, that some software needs grayscale image files to have three channels.

viewtopic.php?t=28453

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According to the changelog

2015-07-25 6.9.2-0 Dirk Lemstra <dirk@lem.....org>
Added "-set colorspace:auto-grayscale=false" that will prevent automatic conversion to grayscale inside coders that support grayscale.
-----------------------------------------------------------

Seen from here, im6.8.9 is not supported.

Thank you again.

Legacy ImageMagick Discussions Archive

Which API to use to force Grayscale to convert RGB?

Which API to use to force Grayscale to convert RGB?

Re: Which API to use to force Grayscale to convert RGB?

Re: Which API to use to force Grayscale to convert RGB?

Re: Which API to use to force Grayscale to convert RGB?

Re: Which API to use to force Grayscale to convert RGB?

Re: Which API to use to force Grayscale to convert RGB?

Re: Which API to use to force Grayscale to convert RGB?