Fix incorrect burnt-in subtitle colours when burning into a DCP source (#2261).

dcp::combined_rgb_to_xyz was changed in libdcp (the values are no longer scaled
by 65535) but DoM wasn't changed, and there was no test to catch it.

diff --git a/src/lib/image.cc b/src/lib/image.cc
index 7b95e67669ae8ca73ba46bab0aaf8bd7a55a1525..f86c105d4f8aa2d2ab76ce465fd8820d44bfa9bd 100644 (file)
--- a/src/lib/image.cc
+++ b/src/lib/image.cc
@@ -730,14 +730,14 @@ Image::alpha_blend (shared_ptr<const Image> other, Position<int> position)
                                double const b = lut_in[op[blue]];
 
                                /* RGB to XYZ, including Bradford transform and DCI companding */
-                               double const x = max (0.0, min (65535.0, r * fast_matrix[0] + g * fast_matrix[1] + b * fast_matrix[2]));
-                               double const y = max (0.0, min (65535.0, r * fast_matrix[3] + g * fast_matrix[4] + b * fast_matrix[5]));
-                               double const z = max (0.0, min (65535.0, r * fast_matrix[6] + g * fast_matrix[7] + b * fast_matrix[8]));
+                               double const x = max(0.0, min(1.0, r * fast_matrix[0] + g * fast_matrix[1] + b * fast_matrix[2]));
+                               double const y = max(0.0, min(1.0, r * fast_matrix[3] + g * fast_matrix[4] + b * fast_matrix[5]));
+                               double const z = max(0.0, min(1.0, r * fast_matrix[6] + g * fast_matrix[7] + b * fast_matrix[8]));
 
                                /* Out gamma LUT and blend */
-                               tp[0] = lrint(lut_out[lrint(x)] * 65535) * alpha + tp[0] * (1 - alpha);
-                               tp[1] = lrint(lut_out[lrint(y)] * 65535) * alpha + tp[1] * (1 - alpha);
-                               tp[2] = lrint(lut_out[lrint(z)] * 65535) * alpha + tp[2] * (1 - alpha);
+                               tp[0] = lrint(lut_out[lrint(x * 65535)] * 65535) * alpha + tp[0] * (1 - alpha);
+                               tp[1] = lrint(lut_out[lrint(y * 65535)] * 65535) * alpha + tp[1] * (1 - alpha);
+                               tp[2] = lrint(lut_out[lrint(z * 65535)] * 65535) * alpha + tp[2] * (1 - alpha);
 
                                tp += this_bpp / 2;
                                op += other_bpp;

diff --git a/test/image_test.cc b/test/image_test.cc
index 8d934bdd62fd429b77e454daf4fcc7917b7e1676..a529a39355f49a643e8fe38af3abaa1b23d5f20c 100644 (file)
--- a/test/image_test.cc
+++ b/test/image_test.cc
@@ -201,6 +201,44 @@ BOOST_AUTO_TEST_CASE (alpha_blend_test)
 }
 
 
+/** Test Image::alpha_blend when the "base" image is XYZ12LE */
+BOOST_AUTO_TEST_CASE (alpha_blend_test_onto_xyz)
+{
+       Image xyz(AV_PIX_FMT_XYZ12LE, dcp::Size(50, 50), Image::Alignment::PADDED);
+       xyz.make_black();
+
+       auto overlay = make_shared<Image>(AV_PIX_FMT_RGBA, dcp::Size(8, 8), Image::Alignment::PADDED);
+       for (int y = 0; y < 8; ++y) {
+               uint8_t* p = overlay->data()[0] + (y * overlay->stride()[0]);
+               for (int x = 0; x < 8; ++x) {
+                       *p++ = 255;
+                       *p++ = 0;
+                       *p++ = 0;
+                       *p++ = 255;
+               }
+       }
+
+       xyz.alpha_blend(overlay, Position<int>(4, 4));
+
+       for (int y = 0; y < 50; ++y) {
+               uint16_t* p = reinterpret_cast<uint16_t*>(xyz.data()[0]) + (y * xyz.stride()[0] / 2);
+               for (int x = 0; x < 50; ++x) {
+                       std::cout << "x=" << x << ", y=" << y << "\n";
+                       if (4 <= x && x < 12 && 4 <= y && y < 12) {
+                               BOOST_REQUIRE_EQUAL(p[0], 45078U);
+                               BOOST_REQUIRE_EQUAL(p[1], 34939U);
+                               BOOST_REQUIRE_EQUAL(p[2], 13892U);
+                       } else {
+                               BOOST_REQUIRE_EQUAL(p[0], 0U);
+                               BOOST_REQUIRE_EQUAL(p[1], 0U);
+                               BOOST_REQUIRE_EQUAL(p[2], 0U);
+                       }
+                       p += 3;
+               }
+       }
+}
+
+
 /** Test merge (list<PositionImage>) with a single image */
 BOOST_AUTO_TEST_CASE (merge_test1)
 {