From 27c0e43d75218b926068fff3d6d1364b476e56ff 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 | 26 +++++++++++++++++++ 3 files changed, 70 insertions(+), 20 deletions(-) diff --git a/src/lib/image.cc b/src/lib/image.cc index 6becdea42..1a5b11ecb 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. @@ -148,8 +165,23 @@ 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 ( @@ -187,35 +219,27 @@ 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)); } @@ -228,7 +252,7 @@ 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 054ce8c17..3b2a8c56d 160000 --- a/test/data +++ b/test/data @@ -1 +1 @@ -Subproject commit 054ce8c174147046d343cf1972e4e1405745ad8f +Subproject commit 3b2a8c56dff15050a9eca576214399ef4a5abc0f diff --git a/test/image_test.cc b/test/image_test.cc index 3c89d5da7..9fe793d70 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" @@ -307,6 +308,31 @@ BOOST_AUTO_TEST_CASE (crop_scale_window_test6) write_image(cropped, "build/test/crop_scale_window_test6.png", "RGB", MagickCore::ShortPixel); } + +/** 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")); + shared_ptr yuv = proxy->image().first->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, + AV_PIX_FMT_RGB24, + true, + false + ); + path file = String::compose("crop_scale_window_test7-%1.png", left_crop); + write_image(cropped, path("build") / "test" / file, "RGB"); + 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")); -- 2.30.2