im.MatrixColor Questions

[Milkymalk]

1. While trying different im.MatrixColor effects I found im.matrix.identity(), which returns a matrix filled with 1s, doing nothing to an image it is applied to. Can you give me an example what I would use this for?

2. How would I use matrix effects for setting the hue of an image, leaving the brightness and saturation alone? im.matrix.hue rotates the hue, so it's not what I am after. In short, if I set the hue to, say, red, then white should stay white, black should stay black, and all shades of color should be set to the red hue. im.matrix.tint doesn't help as it affects saturation, and if I need a matrix for the MatrixColor, I can't figure out the numbers.
2b. Apparently, what I want is akin to the "soft light" layer mode found in graphics software. Is that possible? I have doubts, because all formulas I could find are more complicated than a*b, which is all MatrixColor can do.

[qirien]

1) I'm not sure when you would need it.

2) I am not sure exactly what you are trying to do, but here is some code that turns a sprite orange:

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image him orange = im.MatrixColor("him happy.png",  im.matrix.tint(0.9, 0.7, 0.3))

...and some that turns a sprite green, but it desaturates it first:

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renpy.image("sprite green", im.MatrixColor("sprite.png", im.matrix.desaturate() * im.matrix.tint(0.7, 1.0, 0.7)))

Is one of these kind of what you want?

[Milkymalk]

Unfortunately not, because im.matrix.tint turns white into the tint color. What I want is to preserve brightness and saturation ("strength" of color), only changing the hue (which color it is).
I know there is im.matrix.hue(), but that rotates the hue a certain degree instead of setting it fix to a value.

[qirien]

Do you have some way to store what color you're currently on, and then you could calculate what to pass to im.matrix.hue() based on that? Can you give a few more details -- maybe there's another way to go about it?

[Milkymalk]

Unfortunately not, I would have to analyze every single image that I want to use with this.

I did some research and found several formulas for the "soft light" layer effect. As it seems, it's necessary to reference the color values in order to apply this effect, and there's no way to do that in RenPy. Maybe it could be done by packing the whole formula into the matrix, but the result would be a monstrosity unlike any we have seen in RenPy so far.
I think I will tackle this detail in my game differently.