xps: Convert CMYK with alpha to RGB early to avoid premul alpha headaches.

2 files changed, 18 insertions, 23 deletions

diff --git a/fitz/res_pixmap.c b/fitz/res_pixmap.c
index 9f336ab1..85138be1 100644
--- a/fitz/res_pixmap.c
+++ b/fitz/res_pixmap.c
@@ -106,31 +106,14 @@ fz_premultiplypixmap(fz_pixmap *pix)
 	unsigned char a;
 	int k, x, y;
 
-	/* special case for CMYK (subtractive colors) */
-	if (pix->n == 5)
+	for (y = 0; y < pix->h; y++)
 	{
-		for (y = 0; y < pix->h; y++)
+		for (x = 0; x < pix->w; x++)
 		{
-			for (x = 0; x < pix->w; x++)
-			{
-				a = s[pix->n - 1];
-				for (k = 0; k < pix->n - 1; k++)
-					s[k] = 255 - fz_mul255(255 - s[k], a);
-				s += pix->n;
-			}
-		}
-	}
-	else
-	{
-		for (y = 0; y < pix->h; y++)
-		{
-			for (x = 0; x < pix->w; x++)
-			{
-				a = s[pix->n - 1];
-				for (k = 0; k < pix->n - 1; k++)
-					s[k] = fz_mul255(s[k], a);
-				s += pix->n;
-			}
+			a = s[pix->n - 1];
+			for (k = 0; k < pix->n - 1; k++)
+				s[k] = fz_mul255(s[k], a);
+			s += pix->n;
 		}
 	}
 }
diff --git a/xps/xps_tiff.c b/xps/xps_tiff.c
index c4fdbfcd..384c4338 100644
--- a/xps/xps_tiff.c
+++ b/xps/xps_tiff.c
@@ -832,7 +832,19 @@ xps_decode_tiff(fz_pixmap **imagep, byte *buf, int len)
 
 	/* We should only do this on non-pre-multiplied images, but files in the wild are bad */
 	if (tiff.extrasamples /* == 2 */)
+	{
+		/* CMYK is a subtractive colorspace, we want additive for premul alpha */
+		if (image->n == 5)
+		{
+			fz_pixmap *rgb = fz_newpixmap(fz_devicergb, 0, 0, image->w, image->h);
+			fz_convertpixmap(image, rgb);
+			rgb->xres = image->xres;
+			rgb->yres = image->yres;
+			fz_droppixmap(image);
+			image = rgb;
+		}
 		fz_premultiplypixmap(image);
+	}
 
 	/* Clean up scratch memory */