color banding effect

attribution.txt

@@ -1,2 +1,5 @@
 https://godotshaders.com/shader/color-reduction-and-dither/
 https://godotshaders.com/shader/retro-dither/
+https://godotshaders.com/shader/hsv-adjustment/
+
+https://gist.github.com/msbarry/cd98f928542f5152111a

godot/.mono/metadata/ide_messaging_meta.txt

@@ -0,0 +1,2 @@
+36673
+/home/squirrel/.local/bin/godot_mono

godot/assets/effects/dithering/CanvasLayer.tscn

@@ -4,16 +4,12 @@
 
 [sub_resource type="ShaderMaterial" id=1]
 shader = ExtResource( 1 )
+shader_param/param = 12.0
+shader_param/anim_period = 1.0
 
 [node name="CanvasLayer" type="CanvasLayer"]
 
-[node name="TextureRect" type="TextureRect" parent="."]
+[node name="ColorRect" type="ColorRect" parent="."]
 material = SubResource( 1 )
-anchor_left = 0.5
+anchor_right = 1.0
-anchor_top = 0.5
+anchor_bottom = 1.0
-anchor_right = 0.5
-anchor_bottom = 0.5
-margin_left = -512.0
-margin_top = -300.0
-margin_right = 512.0
-margin_bottom = 300.0

godot/assets/effects/dithering/screen_space_shader.tres

@@ -1,3 +1,127 @@
 [gd_resource type="Shader" format=2]
 
 [resource]
+code = "shader_type canvas_item;
+
+// Color space code from
+// HSV: https://godotshaders.com/shader/hsv-adjustment/
+// LAB/XYZ: https://gist.github.com/msbarry/cd98f928542f5152111a
+// Note: don't use the XYZ space, but sources use it to convert to LAB
+
+
+uniform float param : hint_range(0.0, 255.0, 1.0);
+
+vec3 rgb2hsv(vec3 c) {
+    vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
+    vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));
+    vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));
+
+    float d = q.x - min(q.w, q.y);
+    float e = 1.0e-10;
+    return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
+}
+
+vec3 hsv2rgb(vec3 c) {
+    vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
+    vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
+    return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
+}
+
+vec3 rgb2xyz(vec3 c) {
+  float R = ((c.r > 0.04045) ? pow((( c.r + 0.055 ) / 1.055), 2.4) : (c.r / 12.92)) * 100.0;
+  float G = ((c.g > 0.04045) ? pow((( c.g + 0.055 ) / 1.055), 2.4) : (c.g / 12.92)) * 100.0;
+  float B = ((c.b > 0.04045) ? pow((( c.b + 0.055 ) / 1.055), 2.4) : (c.b / 12.92)) * 100.0;
+
+  float X = R * 0.4124 + G * 0.3576 + B * 0.1805;
+  float Y = R * 0.2126 + G * 0.7152 + B * 0.0722;
+  float Z = R * 0.0193 + G * 0.1192 + B * 0.9505;
+
+  return vec3(X, Y, Z);
+}
+
+vec3 xyz2rgb(vec3 c) {
+  float X = c.x / 100.0;
+  float Y = c.y / 100.0;
+  float Z = c.z / 100.0;
+
+  float R = X *  3.2406 + Y * -1.5372 + Z * -0.4986;
+  float G = X * -0.9689 + Y *  1.8758 + Z *  0.0415;
+  float B = X *  0.0557 + Y * -0.2040 + Z *  1.0570;
+
+  R = ((R > 0.0031308) ? (1.055 * ( pow( R, 1./2.4 ) ) - 0.055) : (12.92 * R)); 
+  G = ((G > 0.0031308) ? (1.055 * ( pow( G, 1./2.4 ) ) - 0.055) : (12.92 * G)); 
+  B = ((B > 0.0031308) ? (1.055 * ( pow( B, 1./2.4 ) ) - 0.055) : (12.92 * B)); 
+
+  return vec3(R, G, B);
+}
+
+vec3 xyz2lab(vec3 c) {
+  float X = c.x / 95.047;
+  float Y = c.y / 100.0;
+  float Z = c.z / 108.883;
+
+  X = ((X > 0.008856) ? (pow( X, 1./3.)) : (( 7.787 * X ) + ( 16./116.)));
+  Y = ((Y > 0.008856) ? (pow( Y, 1./3.)) : (( 7.787 * Y ) + ( 16./116.)));
+  Z = ((Z > 0.008856) ? (pow( Z, 1./3.)) : (( 7.787 * Z ) + ( 16./116.)));
+
+  float L = ( 116. * Y ) - 16.;
+  float a = 500. * ( X - Y );
+  float b = 200. * ( Y - Z );
+
+  return vec3(L, a, b);
+}
+
+vec3 lab2xyz(vec3 c) {
+  float L = c.x;
+  float a = c.y;
+  float b = c.z;
+
+  float Y = ( L + 16. ) / 116.;
+  float X = a / 500. + Y;
+  float Z = Y - b / 200.;
+
+  Y = ((pow(Y,3.) > 0.008856) ? (pow(Y,3.)) : ((Y - 16. / 116.) / 7.787));
+  X = ((pow(X,3.) > 0.008856) ? (pow(X,3.)) : ((X - 16. / 116.) / 7.787));
+  Z = ((pow(Z,3.) > 0.008856) ? (pow(Z,3.)) : ((Z - 16. / 116.) / 7.787));
+
+  float ref_X = 95.047;
+  float ref_Y = 100.0;
+  float ref_Z = 108.883;
+
+  return vec3(ref_X * X, ref_Y * Y, ref_Z * Z);
+}
+
+
+vec3 band_colors(vec3 rgb)
+{	
+	return round(rgb * param) / param;
+}
+
+vec3 band_colors_preserve_hue_lum(vec3 rgb)
+{
+	vec3 hsv = rgb2hsv(rgb);
+	hsv.r = round(hsv.r * param) / param;
+	vec3 lab = xyz2lab(rgb2xyz(rgb));
+	lab.r = round(lab.r * (param / 100.0)) / (param / 100.0);
+	
+	// Into HSV
+	vec2 sv = rgb2hsv(xyz2rgb(lab2xyz(lab))).gb;
+	hsv.gb = sv;
+	return hsv2rgb(hsv);
+}
+
+uniform float anim_period : hint_range(0.1, 5, 0.01);
+
+void fragment()
+{
+	vec3 rgb = textureLod(SCREEN_TEXTURE, SCREEN_UV, 0.0).rgb;
+	vec3 banded_preserved = band_colors_preserve_hue_lum(rgb);
+	vec3 banded_nostalgia = band_colors(rgb);
+	float weight = mod(TIME, anim_period) / anim_period;
+	float double_weight = mod(TIME, anim_period*2.0) / (anim_period*2.0);
+	weight = double_weight > 0.5 ? (1.-weight) : weight;
+	vec3 mixed = mix(banded_nostalgia, banded_preserved, weight);
+	COLOR.rgb = mixed;
+}
+
+"

godot/tests/dither.tscn

@@ -8,6 +8,7 @@
 [node name="Spatial" type="Spatial"]
 
 [node name="CanvasLayer" parent="." instance=ExtResource( 1 )]
+layer = 99
 
 [node name="environment" parent="." instance=ExtResource( 2 )]
 
@@ -22,5 +23,5 @@ environment = SubResource( 1 )
 transform = Transform( 1, 0, 0, 0, 1, 0, 0, 0, 1, -0.00275469, 5.3306, -0.00586939 )
 light_energy = 16.0
 light_indirect_energy = 1.306
-omni_range = 5.778
+omni_range = 8.917
 omni_attenuation = 2.73208