1 files changed, 32 insertions, 0 deletions
diff --git a/source/blender/compositor/realtime_compositor/shaders/library/gpu_shader_compositor_blur_common.glsl b/source/blender/compositor/realtime_compositor/shaders/library/gpu_shader_compositor_blur_common.glsl
new file mode 100644
index 00000000000..e404c03bbb0
--- /dev/null
+++ b/source/blender/compositor/realtime_compositor/shaders/library/gpu_shader_compositor_blur_common.glsl
@@ -0,0 +1,32 @@
+/* Preprocess the input of the blur filter by squaring it in its alpha straight form, assuming the
+ * given color is alpha premultiplied. */
+vec4 gamma_correct_blur_input(vec4 color)
+{
+  /* Unpremultiply alpha. */
+  color.rgb /= color.a > 0.0 ? color.a : 1.0;
+
+  /* Square color channel if it is positive, otherwise zero it. */
+  color.rgb *= mix(color.rgb, vec3(0.0), lessThan(color.rgb, vec3(0.0)));
+
+  /* Premultiply alpha to undo previous alpha unpremultiplication. */
+  color.rgb *= color.a > 0.0 ? color.a : 1.0;
+
+  return color;
+}
+
+/* Postprocess the output of the blur filter by taking its square root it in its alpha straight
+ * form, assuming the given color is alpha premultiplied. This essential undoes the processing done
+ * by the gamma_correct_blur_input function. */
+vec4 gamma_uncorrect_blur_output(vec4 color)
+{
+  /* Unpremultiply alpha. */
+  color.rgb /= color.a > 0.0 ? color.a : 1.0;
+
+  /* Take the square root of the color channel if it is positive, otherwise zero it. */
+  color.rgb = mix(sqrt(color.rgb), vec3(0.0), lessThan(color.rgb, vec3(0.0)));
+
+  /* Premultiply alpha to undo previous alpha unpremultiplication. */
+  color.rgb *= color.a > 0.0 ? color.a : 1.0;
+
+  return color;
+}