Fix corrupted image when over-cropping black filler frames.v2.14.45

FFmpegDecoder can emit small black frames (128x128 pixels) when it
wants to fill in a gap.  Image::crop_scale_window would do the wrong
thing if we then applied a crop of greater than 128 in either direction;
though cropped_size is correctly clamped, the crop value itself was
not and is used to calculate the input data pointers.

This would result in random frames, usually at the end of DCPs,
often made up of blurry colour washes.

1 files changed, 14 insertions, 0 deletions

diff --git a/test/image_test.cc b/test/image_test.cc
index 9fe793d70..2f66cf41d 100644
--- a/test/image_test.cc
+++ b/test/image_test.cc
@@ -393,3 +393,17 @@ BOOST_AUTO_TEST_CASE (fade_test)
 	fade_test_format_red   (AV_PIX_FMT_RGB48LE,   0.5, "rgb48le_50");
 	fade_test_format_red   (AV_PIX_FMT_RGB48LE,   1,   "rgb48le_100");
 }
+
+/** Make sure the image isn't corrupted if it is cropped too much.  This can happen when a
+ *  filler 128x128 black frame is emitted from the FFmpegDecoder and the overall crop in either direction
+ *  is greater than 128 pixels.
+ */
+BOOST_AUTO_TEST_CASE (over_crop_test)
+{
+	shared_ptr<Image> image (new Image (AV_PIX_FMT_RGB24, dcp::Size(128, 128), true));
+	image->make_black ();
+	shared_ptr<Image> scaled = image->crop_scale_window (Crop(0, 0, 128, 128), dcp::Size(1323, 565), dcp::Size(1349, 565), dcp::YUV_TO_RGB_REC709, AV_PIX_FMT_RGB24, true, true);
+	string const filename = "over_crop_test.png";
+	write_image (scaled, "build/test/" + filename, "RGB");
+	check_image ("test/data/" + filename, "build/test/" + filename);
+}