Color management: add "Color Unpremultiply" option for images and render settings.

For premultiplied alpha images, this makes any color space conversion for the image
or render output work on color without alpha multiplied in.

This is typically useful to avoid fringing when the image was or will be composited
over a light background. If the image will be composited over a black background on
the other hand, leaving this option off will give correct results.

In an ideal world, there should never be any color space conversion on images with
alpha, since it's undefined what to do then, but in practice it's useful to have
this option.

Patch by Troy Sobotka, with changes by me.

6 files changed, 34 insertions, 39 deletions

diff --git a/source/blender/editors/include/BIF_glutil.h b/source/blender/editors/include/BIF_glutil.h
index cd3d87a8979..33e9192a23e 100644
--- a/source/blender/editors/include/BIF_glutil.h
+++ b/source/blender/editors/include/BIF_glutil.h
@@ -136,13 +136,8 @@ void glaDrawPixelsSafe		(float x, float y, int img_w, int img_h, int row_w, int
 	 * is expected to be in RGBA byte or float format, and the 
 	 * modelview and projection matrices are assumed to define a 
 	 * 1-to-1 mapping to screen space.
-	 * @param gamma_correct Optionally gamma correct float sources to sRGB for display
 	 */
 
-	/* only for float rects, converts to 32 bits and draws */
-void glaDrawPixelsSafe_to32(float fx, float fy, int img_w, int img_h, int row_w, float *rectf, int gamma_correct);
-
-
 void glaDrawPixelsTex		(float x, float y, int img_w, int img_h, int format, void *rect);
 
 void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format, void *rect, float scaleX, float scaleY);
diff --git a/source/blender/editors/render/render_internal.c b/source/blender/editors/render/render_internal.c
index bff93fea067..e4597d6afc3 100644
--- a/source/blender/editors/render/render_internal.c
+++ b/source/blender/editors/render/render_internal.c
@@ -138,11 +138,14 @@ void image_buffer_rect_update(Scene *scene, RenderResult *rr, ImBuf *ibuf, volat
 	rectf+= 4*(rr->rectx*ymin + xmin);
 	rectc= (unsigned char*)(ibuf->rect + ibuf->x*rymin + rxmin);
 
-	if(scene && (scene->r.color_mgt_flag & R_COLOR_MANAGEMENT))
+	if(scene && (scene->r.color_mgt_flag & R_COLOR_MANAGEMENT)) {
 		profile_from= IB_PROFILE_LINEAR_RGB;
-	else
+		predivide= (scene->r.color_mgt_flag & R_COLOR_MANAGEMENT_PREDIVIDE);
+	}
+	else {
 		profile_from= IB_PROFILE_SRGB;
-	predivide= 0;
+		predivide= 0;
+	}
 
 	IMB_buffer_byte_from_float(rectc, rectf,
 		4, ibuf->dither, IB_PROFILE_SRGB, profile_from, predivide,
diff --git a/source/blender/editors/render/render_preview.c b/source/blender/editors/render/render_preview.c
index feff1e05d60..86328ca2a64 100644
--- a/source/blender/editors/render/render_preview.c
+++ b/source/blender/editors/render/render_preview.c
@@ -460,12 +460,15 @@ static int ed_preview_draw_rect(ScrArea *sa, Scene *sce, ID *id, int split, int
 	Render *re;
 	RenderResult rres;
 	char name[32];
-	int do_gamma_correct=0;
+	int do_gamma_correct=0, do_predivide=0;
 	int offx=0, newx= rect->xmax-rect->xmin, newy= rect->ymax-rect->ymin;
 
 	if (id && GS(id->name) != ID_TE) {
 		/* exception: don't color manage texture previews - show the raw values */
-		if (sce) do_gamma_correct = sce->r.color_mgt_flag & R_COLOR_MANAGEMENT;
+		if (sce) {
+			do_gamma_correct = sce->r.color_mgt_flag & R_COLOR_MANAGEMENT;
+			do_predivide = sce->r.color_mgt_flag & R_COLOR_MANAGEMENT_PREDIVIDE;
+		}
 	}
 
 	if(!split || first) sprintf(name, "Preview %p", (void *)sa);
@@ -488,10 +491,28 @@ static int ed_preview_draw_rect(ScrArea *sa, Scene *sce, ID *id, int split, int
 	if(rres.rectf) {
 		
 		if(ABS(rres.rectx-newx)<2 && ABS(rres.recty-newy)<2) {
+
 			newrect->xmax= MAX2(newrect->xmax, rect->xmin + rres.rectx + offx);
 			newrect->ymax= MAX2(newrect->ymax, rect->ymin + rres.recty);
 
-			glaDrawPixelsSafe_to32(rect->xmin+offx, rect->ymin, rres.rectx, rres.recty, rres.rectx, rres.rectf, do_gamma_correct);
+			if(rres.rectx && rres.recty) {
+				/* temporary conversion to byte for drawing */
+				float fx= rect->xmin + offx;
+				float fy= rect->ymin;
+				int profile_from= (do_gamma_correct)? IB_PROFILE_LINEAR_RGB: IB_PROFILE_SRGB;
+				int dither= 0;
+				unsigned char *rect_byte;
+
+				rect_byte= MEM_mallocN(rres.rectx*rres.recty*sizeof(int), "ed_preview_draw_rect");
+
+				IMB_buffer_byte_from_float(rect_byte, rres.rectf,
+					4, dither, IB_PROFILE_SRGB, profile_from, do_predivide, 
+					rres.rectx, rres.recty, rres.rectx, rres.rectx);
+
+				glaDrawPixelsSafe(fx, fy, rres.rectx, rres.recty, rres.rectx, GL_RGBA, GL_UNSIGNED_BYTE, rect_byte);
+
+				MEM_freeN(rect_byte);
+			}
 
 			RE_ReleaseResultImage(re);
 			return 1;
diff --git a/source/blender/editors/screen/glutil.c b/source/blender/editors/screen/glutil.c
index 8f04940efd6..0b231ee7b96 100644
--- a/source/blender/editors/screen/glutil.c
+++ b/source/blender/editors/screen/glutil.c
@@ -45,9 +45,6 @@
 #include "BIF_gl.h"
 #include "BIF_glutil.h"
 
-#include "IMB_imbuf.h"
-#include "IMB_imbuf_types.h"
-
 #ifndef GL_CLAMP_TO_EDGE
 #define GL_CLAMP_TO_EDGE                        0x812F
 #endif
@@ -562,27 +559,6 @@ void glaDrawPixelsTex(float x, float y, int img_w, int img_h, int format, void *
 	glaDrawPixelsTexScaled(x, y, img_w, img_h, format, rect, 1.0f, 1.0f);
 }
 
-/* row_w is unused but kept for completeness */
-void glaDrawPixelsSafe_to32(float fx, float fy, int img_w, int img_h, int UNUSED(row_w), float *rectf, int do_gamma_correct)
-{
-	unsigned char *rect32;
-	int profile_from= (do_gamma_correct)? IB_PROFILE_LINEAR_RGB: IB_PROFILE_SRGB;
-	int predivide= 0;
-	
-	/* copy imgw-imgh to a temporal 32 bits rect */
-	if(img_w<1 || img_h<1) return;
-	
-	rect32= MEM_mallocN(img_w*img_h*sizeof(int), "temp 32 bits");
-	
-	IMB_buffer_byte_from_float(rect32, rectf,
-		4, 0, IB_PROFILE_SRGB, profile_from, predivide, 
-		img_w, img_h, img_w, img_w);
-	
-	glaDrawPixelsSafe(fx, fy, img_w, img_h, img_w, GL_RGBA, GL_UNSIGNED_BYTE, rect32);
-
-	MEM_freeN(rect32);
-}
-
 void glaDrawPixelsSafe(float x, float y, int img_w, int img_h, int row_w, int format, int type, void *rect)
 {
 	float xzoom= glaGetOneFloat(GL_ZOOM_X);
diff --git a/source/blender/editors/space_image/image_buttons.c b/source/blender/editors/space_image/image_buttons.c
index c647ff3df53..8d8c79386c5 100644
--- a/source/blender/editors/space_image/image_buttons.c
+++ b/source/blender/editors/space_image/image_buttons.c
@@ -750,7 +750,9 @@ void uiTemplateImage(uiLayout *layout, bContext *C, PointerRNA *ptr, const char
 					uiLayoutSetActive(row, RNA_boolean_get(&imaptr, "use_fields"));
 					uiItemR(row, &imaptr, "field_order", UI_ITEM_R_EXPAND, NULL, ICON_NONE);
 					
-					uiItemR(split, &imaptr, "use_premultiply", 0, NULL, ICON_NONE);
+					row= uiLayoutRow(layout, 0);
+					uiItemR(row, &imaptr, "use_premultiply", 0, NULL, ICON_NONE);
+					uiItemR(row, &imaptr, "use_color_unpremultiply", 0, NULL, ICON_NONE);
 				}
 			}
 
diff --git a/source/blender/editors/space_node/space_node.c b/source/blender/editors/space_node/space_node.c
index 1a808e8ee5f..9d4c5705bd1 100644
--- a/source/blender/editors/space_node/space_node.c
+++ b/source/blender/editors/space_node/space_node.c
@@ -248,12 +248,10 @@ static void node_area_listener(ScrArea *sa, wmNotifier *wmn)
 		case NC_IMAGE:
 			if (wmn->action == NA_EDITED) {
 				if(type==NTREE_COMPOSIT) {
-					Scene *scene= wmn->window->screen->scene;
-					
 					/* note that nodeUpdateID is already called by BKE_image_signal() on all
 					 * scenes so really this is just to know if the images is used in the compo else
 					 * painting on images could become very slow when the compositor is open. */
-					if(nodeUpdateID(scene->nodetree, wmn->reference))
+					if(nodeUpdateID(snode->nodetree, wmn->reference))
 						ED_area_tag_refresh(sa);
 				}
 			}