Attempting to render a JPEG with xres and yres set to 1 fails.

We end up trying to scale the JPEG up 72 times and fail a malloc.

A better plan is to make the image handler disbelieve any xres or
yres values less than 72dpi. We take care to still preserve aspect
ratios etc.

1 files changed, 42 insertions, 0 deletions

diff --git a/source/fitz/image.c b/source/fitz/image.c
index 556e841b..09d39043 100644
--- a/source/fitz/image.c
+++ b/source/fitz/image.c
@@ -1,5 +1,7 @@
 #include "mupdf/fitz.h"
 
+#define SANE_DPI 72.0f
+
 fz_pixmap *
 fz_new_pixmap_from_image(fz_context *ctx, fz_image *image, int w, int h)
 {
@@ -542,3 +544,43 @@ fz_new_image_from_buffer(fz_context *ctx, fz_buffer *buffer)
 
 	return fz_new_image(ctx, w, h, 8, cspace, xres, yres, 0, 0, NULL, NULL, bc, NULL);
 }
+
+void
+fz_image_get_sanitised_res(fz_image *image, int *xres, int *yres)
+{
+	*xres = image->xres;
+	*yres = image->yres;
+	if (*xres < 0 || *yres < 0 || (*xres == 0 && *yres == 0))
+	{
+		/* If neither xres or yres is sane, pick a sane value */
+		*xres = SANE_DPI; *yres = SANE_DPI;
+	}
+	else if (*xres == 0)
+	{
+		*xres = *yres;
+	}
+	else if (*yres == 0)
+	{
+		*yres = *xres;
+	}
+
+	/* Scale xres and yres up until we get beleivable values */
+	if (*xres < SANE_DPI || *yres < SANE_DPI)
+	{
+		if (*xres == *yres)
+		{
+			*xres = SANE_DPI;
+			*yres = SANE_DPI;
+		}
+		else if (*xres < *yres)
+		{
+			*yres = *yres * SANE_DPI / *xres;
+			*xres = SANE_DPI;
+		}
+		else
+		{
+			*xres = *xres * SANE_DPI / *yres;
+			*yres = SANE_DPI;
+		}
+	}
+}