From 17959746895a04bd20cc20cd8bdde91d71570b53 Mon Sep 17 00:00:00 2001 From: Carl Hetherington Date: Tue, 17 Nov 2020 00:00:50 +0100 Subject: [PATCH] Fix cropping of subsampled images. The calculations for how to crop subsampled components of YUV images were wrong, causing strange effects like misregistration of colour components in cropped images. Should fix #1872. --- src/lib/image.cc | 62 ++++++++++++++++++++++++++++++++-------------- test/data | 2 +- test/image_test.cc | 28 +++++++++++++++++++++ 3 files changed, 72 insertions(+), 20 deletions(-) diff --git a/src/lib/image.cc b/src/lib/image.cc index 9a9fb8c43..abbc6e71a 100644 --- a/src/lib/image.cc +++ b/src/lib/image.cc @@ -122,6 +122,23 @@ Image::planes () const return d->nb_components; } + +static +int +round_width_for_subsampling (int p, AVPixFmtDescriptor const * desc) +{ + return p & ~ ((1 << desc->log2_chroma_w) - 1); +} + + +static +int +round_height_for_subsampling (int p, AVPixFmtDescriptor const * desc) +{ + return p & ~ ((1 << desc->log2_chroma_h) - 1); +} + + /** Crop this image, scale it to `inter_size' and then place it in a black frame of `out_size'. * @param crop Amount to crop by. * @param inter_size Size to scale the cropped image to. @@ -158,8 +175,23 @@ Image::crop_scale_window ( shared_ptr out (new Image(out_format, out_size, out_aligned)); out->make_black (); + AVPixFmtDescriptor const * in_desc = av_pix_fmt_desc_get (_pixel_format); + if (!in_desc) { + throw PixelFormatError ("crop_scale_window()", _pixel_format); + } + + /* Round down so that we crop only the number of pixels that is straightforward + * considering any subsampling. + */ + Crop rounded_crop( + round_width_for_subsampling(crop.left, in_desc), + round_width_for_subsampling(crop.right, in_desc), + round_height_for_subsampling(crop.top, in_desc), + round_height_for_subsampling(crop.bottom, in_desc) + ); + /* Size of the image after any crop */ - dcp::Size const cropped_size = crop.apply (size ()); + dcp::Size const cropped_size = rounded_crop.apply (size()); /* Scale context for a scale from cropped_size to inter_size */ struct SwsContext* scale_context = sws_getContext ( @@ -196,35 +228,27 @@ Image::crop_scale_window ( 0, 1 << 16, 1 << 16 ); - AVPixFmtDescriptor const * in_desc = av_pix_fmt_desc_get (_pixel_format); - if (!in_desc) { - throw PixelFormatError ("crop_scale_window()", _pixel_format); - } - /* Prepare input data pointers with crop */ uint8_t* scale_in_data[planes()]; for (int c = 0; c < planes(); ++c) { - /* To work out the crop in bytes, start by multiplying - the crop by the (average) bytes per pixel. Then - round down so that we don't crop a subsampled pixel until - we've cropped all of its Y-channel pixels. - */ - int const x = lrintf (bytes_per_pixel(c) * crop.left) & ~ ((int) in_desc->log2_chroma_w); - scale_in_data[c] = data()[c] + x + stride()[c] * (crop.top / vertical_factor(c)); + int const x = lrintf(bytes_per_pixel(c) * rounded_crop.left); + scale_in_data[c] = data()[c] + x + stride()[c] * (rounded_crop.top / vertical_factor(c)); } - /* Corner of the image within out_size */ - Position const corner ((out_size.width - inter_size.width) / 2, (out_size.height - inter_size.height) / 2); - AVPixFmtDescriptor const * out_desc = av_pix_fmt_desc_get (out_format); if (!out_desc) { throw PixelFormatError ("crop_scale_window()", out_format); } + /* Corner of the image within out_size */ + Position const corner ( + round_width_for_subsampling((out_size.width - inter_size.width) / 2, out_desc), + round_height_for_subsampling((out_size.height - inter_size.height) / 2, out_desc) + ); + uint8_t* scale_out_data[out->planes()]; for (int c = 0; c < out->planes(); ++c) { - /* See the note in the crop loop above */ - int const x = lrintf (out->bytes_per_pixel(c) * corner.x) & ~ ((int) out_desc->log2_chroma_w); + int const x = lrintf(out->bytes_per_pixel(c) * corner.x); scale_out_data[c] = out->data()[c] + x + out->stride()[c] * (corner.y / out->vertical_factor(c)); } @@ -237,7 +261,7 @@ Image::crop_scale_window ( sws_freeContext (scale_context); - if (crop != Crop() && cropped_size == inter_size && _pixel_format == out_format) { + if (rounded_crop != Crop() && cropped_size == inter_size) { /* We are cropping without any scaling or pixel format conversion, so FFmpeg may have left some data behind in our image. Clear it out. It may get to the point where we should just stop trying to be clever with cropping. diff --git a/test/data b/test/data index afc239690..30022e624 160000 --- a/test/data +++ b/test/data @@ -1 +1 @@ -Subproject commit afc23969020af54cfb5e6e2f368ca7d395ae4282 +Subproject commit 30022e624852127f464933f5008f8ac6226d831c diff --git a/test/image_test.cc b/test/image_test.cc index 2f2c9a9b7..0aa450321 100644 --- a/test/image_test.cc +++ b/test/image_test.cc @@ -24,6 +24,7 @@ * @see test/make_black_test.cc, test/pixel_formats_test.cc */ +#include "lib/compose.hpp" #include "lib/image.h" #include "lib/ffmpeg_image_proxy.h" #include "test.h" @@ -325,6 +326,33 @@ BOOST_AUTO_TEST_CASE (crop_scale_window_test6) check_image("test/data/crop_scale_window_test6.png", "build/test/crop_scale_window_test6.png", 35000); } + +/** Test some small crops with an image that shows up errors in registration of the YUV planes (#1872) */ +BOOST_AUTO_TEST_CASE (crop_scale_window_test7) +{ + using namespace boost::filesystem; + for (int left_crop = 0; left_crop < 8; ++left_crop) { + shared_ptr proxy(new FFmpegImageProxy("test/data/rgb_grey_testcard.png", VIDEO_RANGE_FULL)); + shared_ptr yuv = proxy->image().image->convert_pixel_format(dcp::YUV_TO_RGB_REC709, AV_PIX_FMT_YUV420P, true, false); + int rounded = left_crop - (left_crop % 2); + shared_ptr cropped = yuv->crop_scale_window( + Crop(left_crop, 0, 0, 0), + dcp::Size(1998 - rounded, 1080), + dcp::Size(1998 - rounded, 1080), + dcp::YUV_TO_RGB_REC709, + VIDEO_RANGE_VIDEO, + AV_PIX_FMT_RGB24, + VIDEO_RANGE_VIDEO, + true, + false + ); + path file = String::compose("crop_scale_window_test7-%1.png", left_crop); + write_image(cropped, path("build") / "test" / file); + check_image(path("test") / "data" / file, path("build") / "test" / file, 10); + } +} + + BOOST_AUTO_TEST_CASE (as_png_test) { shared_ptr proxy(new FFmpegImageProxy("test/data/3d_test/000001.png", VIDEO_RANGE_FULL)); -- 2.30.2