Color X-ray

Ωmega Labs

Coloring X-ray (or any 2 colored) pictures:

X-ray pictures can be done with 2 different methods, mostly with an intensifying screen. We can make a photo simple by using a digital camera with long exposure, or by making a cassette with an X-ray (or photographic) film. Both methods producing a 2 colored pictures, but we want 3 colored RGB pictures, right? : )
First, we need some good photo editor, I’ll use Photoshop to show, how it’s done. Actually my PS is hungarian, and I can’t modify the language, so it will be a little tricky, but there will be pictures to show the steps. But first, if you need the picture for some special measurement or anything, be very careful, as you can modify the information of the picture (of course not only the color, but the contrast, and ratio between colors, so the illuminated materials thicknesses will affect on the picture). I found a pretty easy way to color an image.
Ok, so the first step, open your picture, make a layer from background. It’s likely to open good, sharp, detailed pictures, not every picture will look good after the coloring (if your goal is only to give it a nice look).
Then go to picture->mode->grayscale (to remove all the color information). A question will appear, yes you want to remove the color information.


	Then go again to picture->mode->RGB color. Now we have a grayscale image in RGB mode. It’s easier to do the modification in this way. After this go to picture->corrections->curves.

The curves are the main stuff we need to modify. If you have enough experience, you can color your old black and white photographs, or any other with this. As you see here, there is 4 channels. Now all channels have exactly the same histogram, as we removed the color information, but the picture is now in RGB mode, so the grayscale is built up from RGB colors with additive color mixing. Now comes the real thing, we want to add colors to the picture. But first, we need to think what color will represent which thickness (or material). I’m using now this coloring method: red-green-blue , as thicker-thick-thinner.


	I modified the red channel like this. The first third of the histogram is for the red, but if we want transparency to the other channels (to have yellow, cyan, and magenta), we need to make the curve to reach the other thirds of the histogram, with less intensity.


	The green channel. Note that every picture may need different curves. At this point we’ve lost picture information, as the curves are different.


	Blue channel.


	RGB channel. Yes, sometimes we need to modify it,


	And we’re done. Actually there is several other options to reduce noise, make smoother transparancy between colors


	2 other versions, with selective color change, and another curve modification: