convert/apple image colormap using GIMP gradient (ggr)?

[teridon]

I'd like to apply a GIMP gradient color map (contained in a .ggr file) to an image, but can't figure out how to do it. I couldn't find this on the forum or via Google but maybe because I don't have the right jargon.

I tried using

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convert file.jpg -clut foo.ggr out.jpg

but it appears imagemagick doesn't understand the ggr format. ("no decode delegate for this image format `GGR'")

Do I need to create an actual image from the GGR so that "convert" understands it? I found many programs that convert an image to a ggr but not the other way around.

Example ggr file: https://github.com/Helioviewer-Project/ ... AIA304.ggr

Example source image (grayscale): http://i.imgur.com/tvOJKAj.jpg
Example desired result: http://i.imgur.com/JWcQmdm.jpg

If it matters, I'm using ImageMagick 6.9.0-6 Q16 x64 2015-02-07 on Windows 7 x64.

[fmw42]

IM knows nothing about GIMP ggr files.

See Hald Clut at http://www.imagemagick.org/Usage/color_mods/#hald-clut

1. Create the base hald image in Imagemagick (use at least HALD:8)
2. Take it to GIMP and apply your colortable to the Hald image and save as 24-bit PNG (not JPG or any compressed format)
3. Bring the modified hald image back to IM and apply it using

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convert yourimage modifiedhaldimage.png -hald-clut resultimage

[teridon]

Thanks.

I created a base hald image via:

Code: Select all

convert hald:8 hald.png

Then I attempted to apply the color gradient. I opened it in GIMP, and used the "blend" tool to apply the desired gradient. (mode: normal, shape: linear). Then I exported it as PNG. This is the gradient map: http://i.imgur.com/YlGlqb5.jpg It doesn't really look like a clut any more so I imagine I did something wrong.

In any case, then I converted it using -hald-clut. The result is not at all what I expected. http://i.imgur.com/hluZ9vx.jpg

I also tried other blend modes (darken, additive, multiply, etc.). Some of these looked more like the hald color map, but still after using them with -hald-clut, none of them gave me the result I want -- and they all had the blocky appearance of the one above.

I suppose this is more a GIMP question than IM, so I can take this over to the GIMP forums... I'll report back if someone there tells me what I'm doing wrong.

[teridon]

I figured out what I was doing wrong in GIMP. Here are the complete steps in GIMP (assuming the ggr file is installed in your "gradients" folder)

1. Open hald.png
2. Select All
3. In the Layers Dialog, select the Gradient Tool, then select the desired gradient
4. Apply the gradient by selecting Colors -> Map -> Gradient Map
5. Export the file by selecting File -> Export As ...

Then use -hald-clut as above.

[fmw42]

Do NOT save the modified hald image as JPG or any compressed format or your result will be distorted due to the compression

[teridon]

Thanks for your help!

[fmw42]

You are welcome