Got some basic palette swapping to work. What you’re seeing here is not an image swap, I’m actually using a fragment shader to swap the default green to either blue or red.
Credits to https://github.com/thomasgoldstein/zabuyaki for this shader.
// just an example value for colorCount
const int colorCount = 3;
uniform vec4 originalColors[colorCount];
uniform vec4 alternateColors[colorCount];
vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords) {
// This is the current pixel color
vec4 pixel = Texel(texture, texture_coords);
for (int i = 0; i < colorCount; ++i){
if (pixel == originalColors[i]) {
return alternateColors[i] * color;
}
}
return pixel * color;
}Here is how I generate palette swap shaders given two color tables.
local lume = require 'lume'
local function makePaletteShader(originalColors, alternateColors)
assert(lume.count(originalColors) == lume.count(alternateColors), 'OriginalColors and AlternateColors array length need to match for palette shader')
if #originalColors == 0 then return nil end
local count = #originalColors
local shaderCode = 'const int colorCount = ' .. tostring(count) .. ';'
shaderCode = shaderCode .. [[
uniform vec4 originalColors[colorCount];
uniform vec4 alternateColors[colorCount];
vec4 effect(vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords) {
// This is the current pixel color
vec4 pixel = Texel(texture, texture_coords);
for (int i = 0; i < colorCount; ++i) {
if (pixel == originalColors[i]) {
// return alternate color if it matches an specified original color
return alternateColors[i] * color;
}
}
// return default color if it does not match any of the designated original colors
return pixel * color;
}
]]
local shader = love.graphics.newShader(shaderCode)
if #self.originalColors == 1 then
self.shader:sendColor('originalColors', self.originalColors[1])
self.shader:sendColor('alternateColors', self.alternateColors[1])
else
local otherOrignalColors = lume.slice(self.originalColors, 1)
local otherAlternateColors = lume.slice(self.alternateColors, 1)
self.shader:sendColor('originalColors', self.originalColors[1], otherOrignalColors)
self.shader:sendColor('alternateColors', self.alternateColors[1], otherAlternateColors)
end
end