1 files changed, 56 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/extras/hlg.cc b/third_party/jpeg-xl/lib/extras/hlg.cc
new file mode 100644
index 0000000000..e39a0807f5
--- /dev/null
+++ b/third_party/jpeg-xl/lib/extras/hlg.cc
@@ -0,0 +1,56 @@
+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "lib/extras/hlg.h"
+
+#include <cmath>
+
+#include "lib/jxl/enc_color_management.h"
+
+namespace jxl {
+
+float GetHlgGamma(const float peak_luminance, const float surround_luminance) {
+  return 1.2f * std::pow(1.111f, std::log2(peak_luminance / 1000.f)) *
+         std::pow(0.98f, std::log2(surround_luminance / 5.f));
+}
+
+Status HlgOOTF(ImageBundle* ib, const float gamma, ThreadPool* pool) {
+  ColorEncoding linear_rec2020;
+  linear_rec2020.SetColorSpace(ColorSpace::kRGB);
+  linear_rec2020.primaries = Primaries::k2100;
+  linear_rec2020.white_point = WhitePoint::kD65;
+  linear_rec2020.tf.SetTransferFunction(TransferFunction::kLinear);
+  JXL_RETURN_IF_ERROR(linear_rec2020.CreateICC());
+  JXL_RETURN_IF_ERROR(ib->TransformTo(linear_rec2020, GetJxlCms(), pool));
+
+  JXL_RETURN_IF_ERROR(RunOnPool(
+      pool, 0, ib->ysize(), ThreadPool::NoInit,
+      [&](const int y, const int thread) {
+        float* const JXL_RESTRICT rows[3] = {ib->color()->PlaneRow(0, y),
+                                             ib->color()->PlaneRow(1, y),
+                                             ib->color()->PlaneRow(2, y)};
+        for (size_t x = 0; x < ib->xsize(); ++x) {
+          float& red = rows[0][x];
+          float& green = rows[1][x];
+          float& blue = rows[2][x];
+          const float luminance =
+              0.2627f * red + 0.6780f * green + 0.0593f * blue;
+          const float ratio = std::pow(luminance, gamma - 1);
+          if (std::isfinite(ratio)) {
+            red *= ratio;
+            green *= ratio;
+            blue *= ratio;
+          }
+        }
+      },
+      "HlgOOTF"));
+  return true;
+}
+
+Status HlgInverseOOTF(ImageBundle* ib, const float gamma, ThreadPool* pool) {
+  return HlgOOTF(ib, 1.f / gamma, pool);
+}
+
+}  // namespace jxl