Add ColorCorrection to orx-fx

orx-fx/src/main/kotlin/color/ColorCorrection.kt

@@ -0,0 +1,28 @@
+package org.openrndr.extra.fx.color
+
+import org.openrndr.draw.*
+import org.openrndr.extra.fx.filterFragmentCode
+import org.openrndr.extra.parameters.Description
+import org.openrndr.extra.parameters.DoubleParameter
+
+@Description("Color correction")
+class ColorCorrection : Filter(Shader.createFromCode(filterVertexCode, filterFragmentCode("color/color-correction.frag"))) {
+    @DoubleParameter("brightness", -1.0, 1.0, order = 0)
+    var brightness: Double by parameters
+
+    @DoubleParameter("contrast", -1.0, 1.0, order = 1)
+    var contrast: Double by parameters
+
+    @DoubleParameter("saturation", -1.0, 1.0, order = 2)
+    var saturation: Double by parameters
+
+    @DoubleParameter("hue shift", -180.0, 180.0, order = 3)
+    var hueShift: Double by parameters
+
+    init {
+        contrast = 0.0
+        brightness = 0.0
+        saturation = 0.0
+        hueShift = 0.0
+    }
+}

orx-fx/src/main/resources/org/openrndr/extra/fx/gl3/color/color-correction.frag

@@ -0,0 +1,62 @@
+/* based on "Brightness, contrast, saturation" by WojtaZam: https://www.shadertoy.com/view/XdcXzn */
+
+#version 330 core
+
+uniform float brightness;
+uniform float saturation;
+uniform float contrast;
+uniform float hueShift;
+
+uniform sampler2D tex0;
+in vec2 v_texCoord0;
+out vec4 o_color;
+
+mat4 brightnessMatrix(float brightness) {
+    return mat4(1, 0, 0, 0,
+    0, 1, 0, 0,
+    0, 0, 1, 0,
+    brightness, brightness, brightness, 1);
+}
+
+mat4 contrastMatrix(float contrast) {
+    float t = (1.0 - contrast) / 2.0;
+    return mat4(contrast, 0, 0, 0,
+    0, contrast, 0, 0,
+    0, 0, contrast, 0,
+    t, t, t, 1 );
+}
+
+mat4 saturationMatrix(float saturation) {
+    vec3 luminance = vec3(0.3086, 0.6094, 0.0820);
+    float oneMinusSat = 1.0 - saturation;
+    vec3 red = vec3(luminance.x * oneMinusSat);
+    red += vec3(saturation, 0, 0);
+
+    vec3 green = vec3(luminance.y * oneMinusSat);
+    green += vec3(0, saturation, 0);
+
+    vec3 blue = vec3(luminance.z * oneMinusSat);
+    blue += vec3(0, 0, saturation);
+
+    return mat4(red, 0,
+        green, 0,
+        blue, 0,
+        0, 0, 0, 1 );
+}
+
+// from starea's https://www.shadertoy.com/view/MdjBRy, which in turn remixed it from mAlk's https://www.shadertoy.com/view/MsjXRt
+vec3 shiftHue(in vec3 col, in float Shift) {
+    vec3 P = vec3(0.55735) * dot(vec3(0.55735), col);
+    vec3 U = col - P;
+    vec3 V = cross(vec3(0.55735), U);
+    col = U * cos(Shift * 6.2832) + V * sin(Shift * 6.2832) + P;
+    return col;
+}
+
+void main() {
+    vec4 color = texture(tex0, v_texCoord0);
+    vec4 nc = (color.a == 0.0) ? vec4(0.0) : vec4(color.rgb / color.a, color.a);
+    nc.rgb = shiftHue(nc.rgb, (hueShift/360.0));
+    vec4 cc = brightnessMatrix(brightness) * contrastMatrix((contrast + 1)) * saturationMatrix(saturation + 1) * nc;
+    o_color = vec4(cc.rgb, 1.0) * color.a;
+}