Implement oklab, oklch color space conversion functions, add example, restructure comments in the shaderlib, implements #37

examples/oklab.gdshader

@@ -0,0 +1,12 @@
+shader_type canvas_item;
+
+#include "res://shaderlib/colorspaces.gdshaderinc"
+
+//!load ./images/swamp.jpg
+
+void fragment() {
+	vec4 oklab = rgb2oklab(COLOR);
+	vec4 oklch = oklab2oklch(oklab);
+	oklch.z -= 2.0;
+	COLOR = oklab2rgb(oklch2oklab(oklch));
+}

shaderlib/blur.gdshaderinc

@@ -1,7 +1,9 @@
 
-// gaussian_blur adapted from https://godotshaders.com/shader/customizable-gausian-blur/
+/*
-// original code by https://godotshaders.com/author/djbob-gaming-yt/
+	gaussian_blur adapted from https://godotshaders.com/shader/customizable-gausian-blur/
-// maximum radius is 64
+	original code by https://godotshaders.com/author/djbob-gaming-yt/
+	maximum radius is 64
+*/
 vec4 gaussian_blur(sampler2D texture, vec2 uv, int radius, float sigma) {
 	vec2 resolution = 1.0 / vec2(textureSize(texture, 0));
 	// calculate kernel

shaderlib/colorspaces.gdshaderinc

@@ -1,7 +1,16 @@
 
-// rgb2hsv and hsv2rgb functions adapted
+/*
-// from https://godotshaders.com/shader/hsv-adjustment/
+	Color space conversion functions always work with vec4.
-// original code by https://godotshaders.com/author/al1-ce/
+	The fourth value is always alpha.
+*/
+
+#include "res://shaderlib/common.gdshaderinc"
+
+/*
+	rgb2hsv and hsv2rgb functions adapted
+	from https://godotshaders.com/shader/hsv-adjustment/
+	original code by https://godotshaders.com/author/al1-ce/
+*/
 
 // Convert RGB to HSV (hue, saturation, brightness)
 vec4 rgb2hsv(vec4 c) {
@@ -20,3 +29,62 @@ vec4 hsv2rgb(vec4 c) {
 	vec3 rgb =  c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
 	return vec4(rgb.r, rgb.g, rgb.b, c.a);
 }
+
+/*
+	OkLab and OkLCh
+	For more details on oklab, see
+		- https://bottosson.github.io/posts/oklab/
+		- https://en.wikipedia.org/wiki/Oklab_color_space
+*/
+
+vec4 rgb2oklab(vec4 c) {
+	float l = 0.4122214708f * c.r + 0.5363325363f * c.g + 0.0514459929f * c.b;
+	float m = 0.2119034982f * c.r + 0.6806995451f * c.g + 0.1073969566f * c.b;
+	float s = 0.0883024619f * c.r + 0.2817188376f * c.g + 0.6299787005f * c.b;
+
+	float l_ = cbrt(l);
+	float m_ = cbrt(m);
+	float s_ = cbrt(s);
+
+	return vec4(
+		0.2104542553f*l_ + 0.7936177850f*m_ - 0.0040720468f*s_,
+		1.9779984951f*l_ - 2.4285922050f*m_ + 0.4505937099f*s_,
+		0.0259040371f*l_ + 0.7827717662f*m_ - 0.8086757660f*s_,
+		c.a
+	);
+}
+
+vec4 oklab2rgb(vec4 c) {
+	float l_ = c.x + 0.3963377774f * c.y + 0.2158037573f * c.z;
+	float m_ = c.x - 0.1055613458f * c.y - 0.0638541728f * c.z;
+	float s_ = c.x - 0.0894841775f * c.y - 1.2914855480f * c.z;
+
+	float l = l_*l_*l_;
+	float m = m_*m_*m_;
+	float s = s_*s_*s_;
+
+	return vec4(
+		+4.0767416621f * l - 3.3077115913f * m + 0.2309699292f * s,
+		-1.2684380046f * l + 2.6097574011f * m - 0.3413193965f * s,
+		-0.0041960863f * l - 0.7034186147f * m + 1.7076147010f * s,
+		c.a
+	);
+}
+
+vec4 oklab2oklch(vec4 c) {
+	return vec4(
+		c.x,
+		sqrt((c.y * c.y) + (c.z * c.z)),
+		atan(c.z, c.y),
+		c.a
+	);
+}
+
+vec4 oklch2oklab(vec4 c) {
+	return vec4(
+		c.x,
+		c.y * cos(c.z),
+		c.y * sin(c.z),
+		c.a
+	);
+}

shaderlib/common.gdshaderinc

@@ -0,0 +1,5 @@
+
+// inefficient cuberoot function
+float cbrt(float x) {
+	return pow(x, 1.0/3.0);
+}

shaderlib/denoise.gdshaderinc

@@ -1,7 +1,9 @@
 
-/* glslSmartDenoise by Michele Morrone, adapted
+/*
+	glslSmartDenoise by Michele Morrone, adapted
 	original code: https://github.com/BrutPitt/glslSmartDeNoise
 	license of the original code:
+
 	BSD 2-Clause License
 
 	Copyright (c) 2019-2020 Michele Morrone

shaderlib/transform.gdshaderinc

@@ -1,6 +1,8 @@
 
-// Load in a texture from a sampler2D with an offset and scale
+/*
-// See examples/place_texture.gdshader
+	Load in a texture from a sampler2D with an offset and scale
+	See examples/place_texture.gdshader
+*/
 vec4 place_texture(sampler2D sampler, vec2 uv, vec2 texture_pixel_size, vec2 offset, vec2 scale) {
 	vec2 texture_size = vec2(textureSize(sampler, 0));
 	// position of current pixel; sample color c

shaderlib/transparency.gdshaderinc

@@ -1,6 +1,8 @@
 
-// Alpha Blending a over b after Bruce A. Wallace
+/*
-// source: https://en.wikipedia.org/wiki/Alpha_compositing
+	Alpha Blending a over b after Bruce A. Wallace
+	source: https://en.wikipedia.org/wiki/Alpha_compositing
+*/
 vec4 alpha_blend(vec4 b, vec4 a) {
 	float alpha = a.a + (b.a * (1.0 - a.a));
 	vec3 col = ((a.rgb*a.a) + ((b.rgb*b.a) * (1.0 - a.a)) / alpha);

src/Editor.gd

@@ -137,7 +137,7 @@ var shaderlib_regex = {
 	"blur": RegEx.create_from_string(r'\s*\#include\s+\"res\:\/\/shaderlib\/blur\.gdshaderinc\"'),
 }
 const shaderlib_functions = {
-	"colorspaces": ["rgb2hsv", "hsv2rgb"],
+	"colorspaces": ["rgb2hsv", "hsv2rgb", "oklab2rgb", "rgb2oklab", "oklab2oklch", "oklch2oklab"],
 	"transform": ["place_texture"],
 	"transparency": ["alpha_blend"],
 	"effects": ["pixelate"],