Modulate only certain pixels of sprite

[zstupan]

Godot Version

v4.2.2.stable.official

Question

I have a white / grayscale sprite that I’d like to change the color of. I do want to keep the colors of the eyes of the character and some highlighting unchanged though.

My initial idea was to create a binary mask image where the pixels that I don’t want modulated are set to black, and the rest to white. I then pass the mask image to a fragment shader as a uniform, as well as the color to modulate with.
Here’s my shader code:

shader_type canvas_item;

uniform sampler2D mask;
uniform vec4 modulate: source_color;

void fragment() {
    vec4 color = texture(TEXTURE,UV);
    vec4 color_mask = texture(mask, UV);
    if (color_mask == vec4(1.)) {
        color *= modulate;
    }
    COLOR = color;
}

This kind of works, but it leaves these pixels around the eyes and the highlight unmodulated for some reason:

How do I fix this? Is this even the right approach for this problem?

[athousandships]

I’d suggest using a special colour for the eyes though and converting that, that way it’ll stick out, or use a soft mask instead of a binary one, so use a texture with white where you want to blend

[zstupan]

I’m not sure I understand, could you elaborate further please?

[athousandships]

Instead of using a bitmap for the area to colour use a texture with soft edges and use it to change the colour by multiplication

[zstupan]

How do I do that?

[athousandships]

I’d say just color *= color_mask but I haven’t tried, you’d need to create the mask though, using perhaps some soft edge tool in an image editor

[athousandships]

You might also need to change the filter for the mask texture, using uniform sampler2D mask: filter_nearest, try that first perhaps, it might cause blurring if filtered

[zstupan]

That was it, thanks!