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Graphics: changing a color - Input Junkie
September 25th, 2010
09:38 am


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Graphics: changing a color
I've got a button master which is in black and white and needs to be in navy blue and white.

Poking around GIMP turns up colorify (which puts a colored filter over an image) and colorize (which seems to do the same thing). Color-selecting for black produces an amazing crawling stripey pattern that doesn't settle into anything useful.

Any recommendations?

I remember seeing a couple or three web-based graphics programs, but I haven't been able to track them down.

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(6 comments | Leave a comment)

[User Picture]
Date:September 25th, 2010 02:11 pm (UTC)
Does GIMP offer color replacement or duotoning? I can think of a few ways to change the color from B&W to something else for Photoshop, but I don't really know GIMP.
[User Picture]
Date:September 25th, 2010 02:39 pm (UTC)
It sounds as if the following will work in GIMP:

Select Tools / Color Tools / Levels. This will bring up a dialog.

Select the "Blue" channel. Raise the black output level (drag the triangle at the left end) to the desired shade of blue. If you want a less pure blue, select the "Red" and "Green" channels and raise the black output levels slightly till you get the color you like. If "Preview" is checked, you'll see the changes in the image as you adjust the settings. Click "OK" when you're satisfied.
[User Picture]
Date:September 25th, 2010 03:30 pm (UTC)
Sounds like the "black" isn't an even shade, which makes colour selecting very difficult.

I don't know GIMP's toolset, but in Paint Shop Pro I'd reduce the colour depth of the original to 1-bit to even out the black, then raise it again to 4-bit or higher. Then I'd do a colour-select for the black and swap with the desired shade of blue.

-- Steve hopes that'll convert over well to GIMP's controls.
[User Picture]
Date:September 25th, 2010 07:28 pm (UTC)
Since the current image is black and white, I'd invert it (making it white letters on a black background), and then turn it into a Layer Mask, applied to a solid-color layer of the shade of blue I wanted. I know how to do this easily in Photoshop, but I don't have GIMP installed.

A Layer Mask is a transparency filter applied to a layer, that makes parts of the layer transparent in proportion to how dark the corresponding part of the mask image is. What I've described above should give you solid-colored letters on a transparent background. Slap a solid white layer underneath, and you're done.
[User Picture]
Date:September 25th, 2010 09:52 pm (UTC)

Magic Wand - fill

In photoshop, one way you could do it: (1) making sure the image was RGB Color, not Grays. (2) using the Magic Wand tool to select all the black pixels (with the correct amount of slop and antialiasing on the selection. Experiment. Then (3) Fill the selection with the foreground color, which you'd set to the blue you want.
[User Picture]
Date:September 26th, 2010 02:37 pm (UTC)
My first thought is that if you want to colorize to change the black in a b&w image, you need to lighten/increase the brightness of the entire image. Increasing the brightness won't do a thing to change pure white, but will turn the black into a grey, which you should then be able to colorize. At least that's the way I'd do it in my 11-year-old version of Paint Shop Pro.
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