PDF Images: Add a flag for if we need to apply the decode array

This avoids us having to check the entire array each time, and
makes the next commit simpler.

3 files changed, 13 insertions, 8 deletions

diff --git a/include/mupdf/fitz/image.h b/include/mupdf/fitz/image.h
index cc521904..77f3488b 100644
--- a/include/mupdf/fitz/image.h
+++ b/include/mupdf/fitz/image.h
@@ -95,6 +95,7 @@ struct fz_image_s
 	unsigned int imagemask:1;
 	unsigned int interpolate:1;
 	unsigned int use_colorkey:1;
+	unsigned int use_decode:1;
 	unsigned int invert_cmyk_jpeg:1;
 	unsigned int decoded:1;
 	unsigned int scalable:1;
diff --git a/source/fitz/draw-unpack.c b/source/fitz/draw-unpack.c
index ba11cd3e..35ee9b41 100644
--- a/source/fitz/draw-unpack.c
+++ b/source/fitz/draw-unpack.c
@@ -231,23 +231,17 @@ fz_decode_tile(fz_context *ctx, fz_pixmap *pix, const float *decode)
 	int stride = pix->stride - pix->w * pix->n;
 	int len;
 	int n = fz_maxi(1, pix->n - pix->alpha);
-	int needed;
 	int k;
 	int h;
 
-	needed = 0;
 	for (k = 0; k < n; k++)
 	{
 		int min = decode[k * 2] * 255;
 		int max = decode[k * 2 + 1] * 255;
 		add[k] = min;
 		mul[k] = max - min;
-		needed |= min != 0 || max != 255;
 	}
 
-	if (!needed)
-		return;
-
 	h = pix->h;
 	while (h--)
 	{
diff --git a/source/fitz/image.c b/source/fitz/image.c
index 77344a16..3420067d 100644
--- a/source/fitz/image.c
+++ b/source/fitz/image.c
@@ -342,7 +342,7 @@ fz_decomp_image_from_stream(fz_context *ctx, fz_stream *stm, fz_compressed_image
 			fz_drop_pixmap(ctx, tile);
 			tile = conv;
 		}
-		else
+		else if (image->use_decode)
 		{
 			fz_decode_tile(ctx, tile, image->decode);
 		}
@@ -770,6 +770,7 @@ fz_new_image(fz_context *ctx, int w, int h, int bpc, fz_colorspace *colorspace,
 		fz_image_get_size_fn *get_size, fz_drop_image_fn *drop)
 {
 	fz_image *image;
+	int i;
 
 	assert(mask == NULL || mask->mask == NULL);
 	assert(size >= sizeof(fz_image));
@@ -792,18 +793,27 @@ fz_new_image(fz_context *ctx, int w, int h, int bpc, fz_colorspace *colorspace,
 	image->use_colorkey = (colorkey != NULL);
 	if (colorkey)
 		memcpy(image->colorkey, colorkey, sizeof(int)*image->n*2);
+	image->use_decode = 0;
 	if (decode)
+	{
 		memcpy(image->decode, decode, sizeof(float)*image->n*2);
+	}
 	else
 	{
 		float maxval = fz_colorspace_is_indexed(ctx, colorspace) ? (1 << bpc) - 1 : 1;
-		int i;
 		for (i = 0; i < image->n; i++)
 		{
 			image->decode[2*i] = 0;
 			image->decode[2*i+1] = maxval;
 		}
 	}
+	for (i = 0; i < image->n; i++)
+	{
+		if (image->decode[i * 2] * 255 != 0 || image->decode[i * 2 + 1] * 255 != 255)
+			break;
+	}
+	if (i != image->n)
+		image->use_decode = 1;
 	image->mask = mask;
 
 	return image;