Fix #32603: Multi-Layer EXR files can't be color managed

Issue was caused by completely different way how multi-layer EXRs are loading,
they're bypassing general image buffer loading functions.

Solved by running color space transformation on render result construction
from multi-layer EXR image.

Also fixed issue with wrong display buffer computing for buffers with less
than 4 channels. Issues were:

- Display buffer is always expected to be RGBA
- OpenColorIO can not apply color space transformations on non-{RGB, RGBA}
  pixels.

4 files changed, 12 insertions, 6 deletions

diff --git a/source/blender/render/extern/include/RE_pipeline.h b/source/blender/render/extern/include/RE_pipeline.h
index b43824d6d5e..c7a8bfeec1d 100644
--- a/source/blender/render/extern/include/RE_pipeline.h
+++ b/source/blender/render/extern/include/RE_pipeline.h
@@ -225,7 +225,7 @@ void RE_PreviewRender(struct Render *re, struct Main *bmain, struct Scene *scene
 
 int RE_ReadRenderResult(struct Scene *scene, struct Scene *scenode);
 int RE_WriteRenderResult(struct ReportList *reports, RenderResult *rr, const char *filename, int compress);
-struct RenderResult *RE_MultilayerConvert(void *exrhandle, int rectx, int recty);
+struct RenderResult *RE_MultilayerConvert(void *exrhandle, const char *colorspace, int predivide, int rectx, int recty);
 
 extern const float default_envmap_layout[];
 int RE_WriteEnvmapResult(struct ReportList *reports, struct Scene *scene, struct EnvMap *env, const char *relpath, const char imtype, float layout[12]);
diff --git a/source/blender/render/intern/include/render_result.h b/source/blender/render/intern/include/render_result.h
index 999fb24ba32..5d61417cbaf 100644
--- a/source/blender/render/intern/include/render_result.h
+++ b/source/blender/render/intern/include/render_result.h
@@ -57,7 +57,7 @@ struct RenderResult *render_result_new(struct Render *re,
 struct RenderResult *render_result_new_full_sample(struct Render *re,
 	struct ListBase *lb, struct rcti *partrct, int crop, int savebuffers);
 
-struct RenderResult *render_result_new_from_exr(void *exrhandle, int rectx, int recty);
+struct RenderResult *render_result_new_from_exr(void *exrhandle, const char *colorspace, int predivide, int rectx, int recty);
 
 /* Merge */
 
diff --git a/source/blender/render/intern/source/pipeline.c b/source/blender/render/intern/source/pipeline.c
index 4a1674b8bca..d22e8f95e01 100644
--- a/source/blender/render/intern/source/pipeline.c
+++ b/source/blender/render/intern/source/pipeline.c
@@ -203,9 +203,9 @@ RenderLayer *RE_GetRenderLayer(RenderResult *rr, const char *name)
 	}
 }
 
-RenderResult *RE_MultilayerConvert(void *exrhandle, int rectx, int recty)
+RenderResult *RE_MultilayerConvert(void *exrhandle, const char *colorspace, int predivide, int rectx, int recty)
 {
-	return render_result_new_from_exr(exrhandle, rectx, recty);
+	return render_result_new_from_exr(exrhandle, colorspace, predivide, rectx, recty);
 }
 
 RenderLayer *render_get_active_layer(Render *re, RenderResult *rr)
diff --git a/source/blender/render/intern/source/render_result.c b/source/blender/render/intern/source/render_result.c
index 2d680bf2e81..0bac26e7e3c 100644
--- a/source/blender/render/intern/source/render_result.c
+++ b/source/blender/render/intern/source/render_result.c
@@ -627,12 +627,13 @@ static void ml_addpass_cb(void *UNUSED(base), void *lay, const char *str, float
 }
 
 /* from imbuf, if a handle was returned we convert this to render result */
-RenderResult *render_result_new_from_exr(void *exrhandle, int rectx, int recty)
+RenderResult *render_result_new_from_exr(void *exrhandle, const char *colorspace, int predivide, int rectx, int recty)
 {
 	RenderResult *rr = MEM_callocN(sizeof(RenderResult), __func__);
 	RenderLayer *rl;
 	RenderPass *rpass;
-	
+	const char *to_colorspace = IMB_colormanagement_role_colorspace_name_get(COLOR_ROLE_SCENE_LINEAR);
+
 	rr->rectx = rectx;
 	rr->recty = recty;
 	
@@ -645,6 +646,11 @@ RenderResult *render_result_new_from_exr(void *exrhandle, int rectx, int recty)
 		for (rpass = rl->passes.first; rpass; rpass = rpass->next) {
 			rpass->rectx = rectx;
 			rpass->recty = recty;
+
+			if (rpass->channels >= 3) {
+				IMB_colormanagement_transform(rpass->rect, rpass->rectx, rpass->recty, rpass->channels,
+				                              colorspace, to_colorspace, predivide);
+			}
 		}
 	}