Palette swap shader not working correctly

[snowystoat]

Godot Version

Godot 4.5

Question

I’m working on a retro-styled game where a lot of visual effects are done via palette swapping. Recently, I’ve finally decided to rework the shader so that it doesn’t have both the original colors array and the original colors image, as that has always seemed redundant to me. However, I can’t get the colors from the palette image to be read correctly.

Original palette:

Old shader, all colors replaced correctly:

New shader, half of the colors failed to replace:

void fragment() {
	vec4 palette[] = {color0, color1, color2, color3, color4, color5, color6, color7};

	int color_count = textureSize(original_palette, 0).x;

	for (int i = 0; i < min(color_count, 8); i++) {
		vec4 color_orig = texture(original_palette, vec2(float(i) / float(color_count - 1), 0));
		if (COLOR == color_orig) {
			COLOR = palette[i];
		}
	}

The only part I can think of that might have anything wrong is the texture division, as the rest seems to work fine. color0-7 are vec4’s, original_palette is a sampler2D.

[hyvernox]

float(i) / float(color_count - 1) results in the texel’s borders for the highest and lowest values, which is probably causing issues when retrieving their colors.
(float(i) + 0.5) / float(color_count) should give you the center of every texel.