pnm: Premultiply alpha for use in pixmap.

1 files changed, 25 insertions, 0 deletions

diff --git a/source/fitz/load-pnm.c b/source/fitz/load-pnm.c
index f585cd8a..7c31c4df 100644
--- a/source/fitz/load-pnm.c
+++ b/source/fitz/load-pnm.c
@@ -531,6 +531,31 @@ pam_binary_read_image(fz_context *ctx, struct info *pnm, unsigned char *p, unsig
 						p += 2;
 					}
 		}
+
+		if (pnm->alpha)
+		{
+			/* CMYK is a subtractive colorspace, we want additive for premul alpha */
+			if (img->n > 4)
+			{
+				fz_pixmap *rgb = fz_new_pixmap(ctx, fz_device_rgb(ctx), img->w, img->h, 1);
+				rgb->xres = img->xres;
+				rgb->yres = img->yres;
+
+				fz_try(ctx)
+				{
+					fz_convert_pixmap(ctx, rgb, img);
+					fz_drop_pixmap(ctx, img);
+					img = rgb;
+					rgb = NULL;
+				}
+				fz_always(ctx)
+					fz_drop_pixmap(ctx, rgb);
+				fz_catch(ctx)
+					fz_rethrow(ctx);
+			}
+
+			fz_premultiply_pixmap(ctx, img);
+		}
 	}
 
 	return img;