Avoid unnecessary alphas when decompressing images from streams.

4 files changed, 17 insertions, 11 deletions

diff --git a/include/mupdf/fitz/image.h b/include/mupdf/fitz/image.h
index 255337ee..9a8d5309 100644
--- a/include/mupdf/fitz/image.h
+++ b/include/mupdf/fitz/image.h
@@ -72,7 +72,7 @@ fz_image *fz_new_image_from_buffer(fz_context *ctx, fz_buffer *buffer);
 fz_image *fz_new_image_from_file(fz_context *ctx, const char *path);
 void fz_drop_image_imp(fz_context *ctx, fz_storable *image);
 fz_pixmap *fz_decomp_image_from_stream(fz_context *ctx, fz_stream *stm, fz_compressed_image *image, fz_irect *subarea, int indexed, int l2factor);
-fz_pixmap *fz_expand_indexed_pixmap(fz_context *ctx, fz_pixmap *src);
+fz_pixmap *fz_expand_indexed_pixmap(fz_context *ctx, const fz_pixmap *src, int alpha);
 size_t fz_image_size(fz_context *ctx, fz_image *im);
 
 struct fz_image_s
diff --git a/source/fitz/colorspace.c b/source/fitz/colorspace.c
index b4d511e8..7923446a 100644
--- a/source/fitz/colorspace.c
+++ b/source/fitz/colorspace.c
@@ -1930,31 +1930,32 @@ fz_new_indexed_colorspace(fz_context *ctx, fz_colorspace *base, int high, unsign
 }
 
 fz_pixmap *
-fz_expand_indexed_pixmap(fz_context *ctx, fz_pixmap *src)
+fz_expand_indexed_pixmap(fz_context *ctx, const fz_pixmap *src, int alpha)
 {
 	struct indexed *idx;
 	fz_pixmap *dst;
-	unsigned char *s, *d;
+	const unsigned char *s;
+	unsigned char *d;
 	int y, x, k, n, high;
 	unsigned char *lookup;
 	fz_irect bbox;
 	int s_line_inc, d_line_inc;
 
 	assert(src->colorspace->to_rgb == indexed_to_rgb);
-	assert(src->n == 2);
+	assert(src->n == 1 + alpha);
 
 	idx = src->colorspace->data;
 	high = idx->high;
 	lookup = idx->lookup;
 	n = idx->base->n;
 
-	dst = fz_new_pixmap_with_bbox(ctx, idx->base, fz_pixmap_bbox(ctx, src, &bbox), src->alpha);
+	dst = fz_new_pixmap_with_bbox(ctx, idx->base, fz_pixmap_bbox(ctx, src, &bbox), alpha);
 	s = src->samples;
 	d = dst->samples;
 	s_line_inc = src->stride - src->w * src->n;
 	d_line_inc = dst->stride - dst->w * dst->n;
 
-	if (src->alpha)
+	if (alpha)
 	{
 		for (y = 0; y < src->h; y++)
 		{
@@ -1962,9 +1963,10 @@ fz_expand_indexed_pixmap(fz_context *ctx, fz_pixmap *src)
 			{
 				int v = *s++;
 				int a = *s++;
+				int aa = a + (a>>7);
 				v = fz_mini(v, high);
 				for (k = 0; k < n; k++)
-					*d++ = fz_mul255(lookup[v * n + k], a);
+					*d++ = (aa * lookup[v * n + k] + 128)>>8;
 				*d++ = a;
 			}
 			s += s_line_inc;
diff --git a/source/fitz/draw-unpack.c b/source/fitz/draw-unpack.c
index ccb3c62f..0211b7e4 100644
--- a/source/fitz/draw-unpack.c
+++ b/source/fitz/draw-unpack.c
@@ -179,7 +179,8 @@ fz_decode_indexed_tile(fz_context *ctx, fz_pixmap *pix, const float *decode, int
 	unsigned char *p = pix->samples;
 	int stride = pix->stride - pix->w * pix->n;
 	int len;
-	int n = pix->n - 1;
+	int pn = pix->n;
+	int n = pn - pix->alpha;
 	int needed;
 	int k;
 	int h;
@@ -208,7 +209,7 @@ fz_decode_indexed_tile(fz_context *ctx, fz_pixmap *pix, const float *decode, int
 				int value = (add[k] + (((p[k] << 8) * mul[k]) >> 8)) >> 8;
 				p[k] = fz_clampi(value, 0, 255);
 			}
-			p += n + 1;
+			p += pn;
 		}
 		p += stride;
 	}
diff --git a/source/fitz/image.c b/source/fitz/image.c
index bd6e0b62..c49580bf 100644
--- a/source/fitz/image.c
+++ b/source/fitz/image.c
@@ -198,7 +198,10 @@ fz_decomp_image_from_stream(fz_context *ctx, fz_stream *stm, fz_compressed_image
 
 	fz_try(ctx)
 	{
-		tile = fz_new_pixmap(ctx, image->colorspace, w, h, 1);
+		int alpha = (image->colorspace == NULL);
+		if (image->use_colorkey)
+			alpha = 1;
+		tile = fz_new_pixmap(ctx, image->colorspace, w, h, alpha);
 		tile->interpolate = image->interpolate;
 
 		stride = (w * image->n * image->bpc + 7) / 8;
@@ -276,7 +279,7 @@ fz_decomp_image_from_stream(fz_context *ctx, fz_stream *stm, fz_compressed_image
 		{
 			fz_pixmap *conv;
 			fz_decode_indexed_tile(ctx, tile, image->decode, (1 << image->bpc) - 1);
-			conv = fz_expand_indexed_pixmap(ctx, tile);
+			conv = fz_expand_indexed_pixmap(ctx, tile, alpha);
 			fz_drop_pixmap(ctx, tile);
 			tile = conv;
 		}