bugfix [#22638] Alpha channel not saved when using texture paint

check for alpha channel while saving images that have been painted onto.
It would be nicer to do this while in paint mode except this isn't so simple with project paint using multiple images at once.

3 files changed, 31 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_image.h b/source/blender/blenkernel/BKE_image.h
index 7a801c0ef0a..46c7cd89ecf 100644
--- a/source/blender/blenkernel/BKE_image.h
+++ b/source/blender/blenkernel/BKE_image.h
@@ -46,6 +46,7 @@ void	free_image(struct Image *me);
 
 void	BKE_stamp_info(struct Scene *scene, struct ImBuf *ibuf);
 void	BKE_stamp_buf(struct Scene *scene, unsigned char *rect, float *rectf, int width, int height, int channels);
+int		BKE_alphatest_ibuf(struct ImBuf *ibuf);
 int		BKE_write_ibuf(struct Scene *scene, struct ImBuf *ibuf, const char *name, int imtype, int subimtype, int quality);
 void	BKE_makepicstring(char *string, const char *base, int frame, int imtype, const short use_ext, const short use_frames);
 int		BKE_add_image_extension(char *string, int imtype);
diff --git a/source/blender/blenkernel/intern/image.c b/source/blender/blenkernel/intern/image.c
index b624feeaf9d..31eae70f159 100644
--- a/source/blender/blenkernel/intern/image.c
+++ b/source/blender/blenkernel/intern/image.c
@@ -1188,6 +1188,29 @@ void BKE_stamp_info(Scene *scene, struct ImBuf *ibuf)
 	if (stamp_data.rendertime[0]) IMB_metadata_change_field (ibuf, "RenderTime", stamp_data.rendertime);
 }
 
+int BKE_alphatest_ibuf(ImBuf *ibuf)
+{
+	int tot;
+	if(ibuf->rect_float) {
+		float *buf= ibuf->rect_float;
+		for(tot= ibuf->x * ibuf->y; tot--; buf+=4) {
+			if(buf[3] < 1.0f) {
+				return TRUE;
+			}
+		}
+	}
+	else if (ibuf->rect) {
+		unsigned char *buf= (unsigned char *)ibuf->rect;
+		for(tot= ibuf->x * ibuf->y; tot--; buf+=4) {
+			if(buf[3] != 255) {
+				return TRUE;
+			}
+		}
+	}
+
+	return FALSE;
+}
+
 int BKE_write_ibuf(Scene *scene, ImBuf *ibuf, const char *name, int imtype, int subimtype, int quality)
 {
 	int ok;
diff --git a/source/blender/editors/space_image/image_ops.c b/source/blender/editors/space_image/image_ops.c
index d2cf3365423..be917f43735 100644
--- a/source/blender/editors/space_image/image_ops.c
+++ b/source/blender/editors/space_image/image_ops.c
@@ -888,6 +888,13 @@ static void save_image_doit(bContext *C, SpaceImage *sima, Scene *scene, wmOpera
 				ibuf->depth= 24;
 			}
 		}
+		else {
+			/* TODO, better solution, if a 24bit image is painted onto it may contain alpha */
+			if(ibuf->userflags & IB_BITMAPDIRTY) { /* it has been painted onto */
+				/* checks each pixel, not ideal */
+				ibuf->depth= BKE_alphatest_ibuf(ibuf) ? 32 : 24;
+			}
+		}
 
 		if(scene->r.scemode & R_EXTENSION)  {
 			BKE_add_image_extension(path, sima->imtypenr);