G’MIC offers a couple of color mixers in different color spaces. Special about them is that you have the choice of mixing colors only in the shadows, in the mid-tones or in the highlights – or all the three of them. Sometimes you can create amazing effects, on the condition that you work with an appropriate photo.
For this example I use a photo of a nice girl wearing big dark sunglasses. In GIMP, open the G’MIC menu under Filters, navigate to the Colors tab on the left and choose Mixer [YCbCr]. That stands for Luminance (Y), chroma-blue (Cb) and chroma-red (Cr) and is (roughly) another color space, like RGB or CMYK. The following window appears.
On the right side, for Tones range, I choose Shadows, because I want to play with the colors of her sunglasses. I start with only two sliders: blue chroma brightness and red chroma brightness. Below some results with the following values: red-chroma +255, red-chroma -255, blue-chroma +255 and blue-chroma -255.
By using different combinations of slider values, we can produce the following colors.
With the bottom slider called Tones smoothness, you can fine-tune the transition between – in this case – the shadows and the mid-tones. More to the right adds some flare to the shadows, while pushing the slider to the left makes the transition less smooth (usually not very attractive).
We can do the same trick using G’MICs other color mixers – RGB, Lab, HSV and CMYK. Below I show just three variants per color space, but you can produce many, many more.
Of course a photo that is treated this way can be fed again to one of the mixers. If we choose this time to work on the highlights, we get for example the following.
We can make things even more cool by using first another G’MIC filter called Decompose channels. This one is also to be found in the Colors section of G’MIC.
Mind the Color basis here, as that has a big influence on the result. Default is Lab.
Following the result with the default Lab color basis, with the option Include opacity layer checked. That produces the empty white space on the right.
Now we apply our YCbCr mixer and that gives something like this.
Another Decomposition to CMYK, followed by the YCbCr mixer working on the mid-tones.
Print, frame and you have 100% real art on your wall!