Fix #33747: do better backwards compatibility for image transparency changes.

The use alpha option moved from the texture datablock to the image, and now it
will duplicate the image datablock in case you have one texture using alpha and
the other not.

source/blender/blenkernel/BKE_image.h

@@ -205,7 +205,7 @@ void BKE_image_memorypack(struct Image *ima);
 void BKE_image_print_memlist(void);
 
 /* empty image block, of similar type and filename */
-struct Image *BKE_image_copy(struct Image *ima);
+struct Image *BKE_image_copy(struct Main *bmain, struct Image *ima);
 
 /* merge source into dest, and free source */
 void BKE_image_merge(struct Image *dest, struct Image *source);

source/blender/blenkernel/intern/image.c

@@ -323,9 +323,9 @@ static void image_assign_ibuf(Image *ima, ImBuf *ibuf, int index, int frame)
 }
 
 /* empty image block, of similar type and filename */
-Image *BKE_image_copy(Image *ima)
+Image *BKE_image_copy(Main *bmain, Image *ima)
 {
-	Image *nima = image_alloc(G.main, ima->id.name + 2, ima->source, ima->type);
+	Image *nima = image_alloc(bmain, ima->id.name + 2, ima->source, ima->type);
 
 	BLI_strncpy(nima->name, ima->name, sizeof(ima->name));
 
@@ -343,6 +343,9 @@ Image *BKE_image_copy(Image *ima)
 
 	BKE_color_managed_colorspace_settings_copy(&nima->colorspace_settings, &ima->colorspace_settings);
 
+	if (ima->packedfile)
+		nima->packedfile = dupPackedFile(ima->packedfile);
+
 	return nima;
 }
 
@@ -433,7 +436,7 @@ void BKE_image_make_local(struct Image *ima)
 		extern_local_image(ima);
 	}
 	else if (is_local && is_lib) {
-		Image *ima_new = BKE_image_copy(ima);
+		Image *ima_new = BKE_image_copy(bmain, ima);
 
 		ima_new->id.us = 0;
 

source/blender/blenkernel/intern/library.c

@@ -312,7 +312,7 @@ int id_copy(ID *id, ID **newid, int test)
 			if (!test) *newid = (ID *)BKE_texture_copy((Tex *)id);
 			return 1;
 		case ID_IM:
-			if (!test) *newid = (ID *)BKE_image_copy((Image *)id);
+			if (!test) *newid = (ID *)BKE_image_copy(G.main, (Image *)id);
 			return 1;
 		case ID_LT:
 			if (!test) *newid = (ID *)BKE_lattice_copy((Lattice *)id);

source/blender/blenloader/intern/readfile.c

@@ -8644,8 +8644,8 @@ static void do_versions(FileData *fd, Library *lib, Main *main)
 
 	if (main->versionfile < 265 || (main->versionfile == 265 && main->subversionfile < 5)) {
 		Scene *scene;
-		Image *image;
-		Tex *tex;
+		Image *image, *nimage;
+		Tex *tex, *otex;
 
 		for (scene = main->scene.first; scene; scene = scene->id.next) {
 			Sequence *seq;
@@ -8664,16 +8664,63 @@ static void do_versions(FileData *fd, Library *lib, Main *main)
 		for (image = main->image.first; image; image = image->id.next) {
 			if (image->flag & IMA_DO_PREMUL)
 				image->alpha_mode = IMA_ALPHA_STRAIGHT;
+
+			image->flag &= ~IMA_DONE_TAG;
 		}
 
+		/* use alpha flag moved from texture to image datablock */
 		for (tex = main->tex.first; tex; tex = tex->id.next) {
 			if (tex->type == TEX_IMAGE && (tex->imaflag & TEX_USEALPHA) == 0) {
 				image = blo_do_versions_newlibadr(fd, tex->id.lib, tex->ima);
 
-				if (image)
+				/* skip if no image or already tested */
+				if (!image || (image->flag & (IMA_DONE_TAG|IMA_IGNORE_ALPHA)))
+					continue;
+
+				image->flag |= IMA_DONE_TAG;
+
+				/* we might have some textures using alpha and others not, so we check if
+				 * they exist and duplicate the image datablock if necessary */
+				for (otex = main->tex.first; otex; otex = otex->id.next)
+					if (otex->type == TEX_IMAGE && (otex->imaflag & TEX_USEALPHA))
+						if (image == blo_do_versions_newlibadr(fd, otex->id.lib, otex->ima))
+							break;
+
+				if (otex) {
+					/* copy image datablock */
+					nimage = BKE_image_copy(main, image);
+					nimage->flag |= IMA_IGNORE_ALPHA|IMA_DONE_TAG;
+					nimage->id.us--;
+
+					/* we need to do some trickery to make file loading think
+					 * this new datablock is part of file we're loading */
+					blo_do_versions_oldnewmap_insert(fd->libmap, nimage, nimage, 0);
+					nimage->id.lib = image->id.lib;
+					nimage->id.flag |= (image->id.flag & LIB_NEED_LINK);
+
+					/* assign new image, and update the users counts accordingly */
+					for (otex = main->tex.first; otex; otex = otex->id.next) {
+						if (otex->type == TEX_IMAGE && (otex->imaflag & TEX_USEALPHA) == 0) {
+							if (image == blo_do_versions_newlibadr(fd, otex->id.lib, otex->ima)) {
+								if (!(otex->id.flag & LIB_NEED_LINK)) {
+									image->id.us--;
+									nimage->id.us++;
+								}
+								otex->ima = nimage;
+								break;
+							}
+						}
+					}
+				}
+				else {
+					/* no other textures using alpha, just set the flag */
 					image->flag |= IMA_IGNORE_ALPHA;
+				}
 			}
 		}
+
+		for (image = main->image.first; image; image = image->id.next)
+			image->flag &= ~IMA_DONE_TAG;
 	}
 
 	if (main->versionfile < 265 || (main->versionfile == 265 && main->subversionfile < 7)) {

source/blender/makesdna/DNA_image_types.h

@@ -125,7 +125,7 @@ typedef struct Image {
 #define IMA_DO_PREMUL		4    /* deprecated, should not be used */
 #define IMA_REFLECT			16
 #define IMA_NOCOLLECT   	32
-#define IMA_DEPRECATED		64
+#define IMA_DONE_TAG		64
 #define IMA_OLD_PREMUL		128
 /*#define IMA_CM_PREDIVIDE	256*/  /* deprecated, should not be used */
 #define IMA_USED_FOR_RENDER	512