1 files changed, 39 insertions, 0 deletions
diff --git a/source/blender/compositor/realtime_compositor/shaders/library/gpu_shader_compositor_hue_correct.glsl b/source/blender/compositor/realtime_compositor/shaders/library/gpu_shader_compositor_hue_correct.glsl
new file mode 100644
index 00000000000..99eb125cdf2
--- /dev/null
+++ b/source/blender/compositor/realtime_compositor/shaders/library/gpu_shader_compositor_hue_correct.glsl
@@ -0,0 +1,39 @@
+#pragma BLENDER_REQUIRE(gpu_shader_common_color_utils.glsl)
+
+/* Curve maps are stored in sampler objects that are evaluated in the [0, 1] range, so normalize
+ * parameters accordingly. */
+#define NORMALIZE_PARAMETER(parameter, minimum, range) ((parameter - minimum) * range)
+
+void node_composite_hue_correct(float factor,
+                                vec4 color,
+                                sampler1DArray curve_map,
+                                const float layer,
+                                vec3 minimums,
+                                vec3 range_dividers,
+                                out vec4 result)
+{
+  vec4 hsv;
+  rgb_to_hsv(color, hsv);
+
+  /* First, adjust the hue channel on its own, since corrections in the saturation and value
+   * channels depends on the new value of the hue, not its original value. A curve map value of 0.5
+   * means no change in hue, so adjust the value to get an identity at 0.5. Since the identity of
+   * addition is 0, we subtract 0.5 (0.5 - 0.5 = 0). */
+  const float hue_parameter = NORMALIZE_PARAMETER(hsv.x, minimums.x, range_dividers.x);
+  hsv.x += texture(curve_map, vec2(hue_parameter, layer)).x - 0.5;
+
+  /* Second, adjust the saturation and value based on the new value of the hue. A curve map value
+   * of 0.5 means no change in hue, so adjust the value to get an identity at 0.5. Since the
+   * identity of duplication is 1, we multiply by 2 (0.5 * 2 = 1). */
+  vec2 parameters = NORMALIZE_PARAMETER(hsv.x, minimums.yz, range_dividers.yz);
+  hsv.y *= texture(curve_map, vec2(parameters.x, layer)).y * 2.0;
+  hsv.z *= texture(curve_map, vec2(parameters.y, layer)).z * 2.0;
+
+  /* Sanitize the new hue and saturation values. */
+  hsv.x = fract(hsv.x);
+  hsv.y = clamp(hsv.y, 0.0, 1.0);
+
+  hsv_to_rgb(hsv, result);
+
+  result = mix(color, result, factor);
+}