intern/opencolorio/gpu_shader_display_transform_frag.glsl

@@ -169,9 +169,16 @@ vec4 OCIO_ProcessColor(vec4 col, vec4 col_overlay)
    * merge UI using alpha blending in the correct color space. */
   if (parameters.use_overlay) {
     col.rgb = pow(col.rgb, vec3(parameters.exponent * 2.2));
+    vec4 clamped_col = clamp(col, 0.0, 1.0);
+
     if (!parameters.use_extended) {
       /* if we're not using an extended colour space, clamp the color 0..1 */
-      col = clamp(col, 0.0, 1.0);
+      col = clamped_col;
+    }
+    else {
+      /* When using extended colorspace, interpolate towards clamped color to improve display of
+       * alpha-blended overlays. */
+      col = mix(col, clamped_col, col_overlay.a);
     }
     col *= 1.0 - col_overlay.a;
     col += col_overlay; /* Assumed unassociated alpha. */

source/blender/gpu/intern/gpu_viewport.c

@@ -451,9 +451,11 @@ static void gpu_viewport_draw_colormanaged(GPUViewport *viewport,
     GPU_batch_program_set_imm_shader(batch);
   }
   else {
+
     GPU_batch_program_set_builtin(batch, GPU_SHADER_2D_IMAGE_OVERLAYS_MERGE);
     GPU_batch_uniform_1i(batch, "overlay", do_overlay_merge);
     GPU_batch_uniform_1i(batch, "display_transform", display_colorspace);
+    GPU_batch_uniform_1i(batch, "use_extended", U.gpu_flag & USER_GPU_FLAG_HDR_ENABLED);
   }
 
   GPU_texture_bind(color, 0);

source/blender/gpu/shaders/gpu_shader_image_overlays_merge_frag.glsl

@@ -36,7 +36,16 @@ void main()
   vec4 overlay_col = texture(overlays_texture, texCoord_interp.xy);
 
   if (overlay) {
-    fragColor = clamp(fragColor, 0.0, 1.0);
+    vec4 clamped_col = clamp(fragColor, 0.0, 1.0);
+    if (!use_extended) {
+      /* Only clamp color if we are not using an extended display colorspace. */
+      fragColor = clamped_col;
+    }
+    else {
+      /* When using extended colorspace, interpolate towards clamped color to avoid over-brightened
+       * overlays. */
+      fragColor = mix(fragColor, clamped_col, overlay_col.a);
+    }
     fragColor *= 1.0 - overlay_col.a;
     fragColor += overlay_col;
   }

source/blender/gpu/shaders/infos/gpu_shader_2D_image_overlays_merge_info.hh

@@ -17,6 +17,7 @@ GPU_SHADER_CREATE_INFO(gpu_shader_2D_image_overlays_merge)
     .push_constant(Type::MAT4, "ModelViewProjectionMatrix")
     .push_constant(Type::BOOL, "display_transform")
     .push_constant(Type::BOOL, "overlay")
+    .push_constant(Type::BOOL, "use_extended")
     /* Sampler slots should match OCIO's. */
     .sampler(0, ImageType::FLOAT_2D, "image_texture")
     .sampler(1, ImageType::FLOAT_2D, "overlays_texture")