Is there a way to change image filter?

Shirted-Vanes

I have colored textures in my game and I want to switch all of them to black-white. The easiest way is to create two versions of texture files: with color and without it. And then in dependence of mode this textures switch. But can I change like... color filter of viewport? Like it does Photoshop, for example.

TwistedTwigleg

Maybe the CanvasModulate (documentation) node? I have not used it with a Viewport myself, but it seems like it would be the ideal node for the job.

SIsilicon28

You can add a custom shader to a ColorRect node for a postprocessing effect. In the case of black n' white, the shader code would look like this.

shader_type canvas_item;
render_mode unshaded;

void fragment() {
    COLOR = texture(SCREEN_TEXTURE, SCREEN_UV);

    float luminance = dot(COLOR.rgb, vec3(0.3, 0.59, 0.11));

    COLOR.rgb = vec3(luminance);
}

To vary the strength of the effect, just change the alpha of the ColorRect's colour. :)