1 files changed, 115 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/alpha.cc b/third_party/jpeg-xl/lib/jxl/alpha.cc
new file mode 100644
index 0000000000..48d7e7ee92
--- /dev/null
+++ b/third_party/jpeg-xl/lib/jxl/alpha.cc
@@ -0,0 +1,115 @@
+// 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/jxl/alpha.h"
+
+#include <string.h>
+
+#include <algorithm>
+
+namespace jxl {
+
+static float Clamp(float x) { return std::max(std::min(1.0f, x), 0.0f); }
+
+void PerformAlphaBlending(const AlphaBlendingInputLayer& bg,
+                          const AlphaBlendingInputLayer& fg,
+                          const AlphaBlendingOutput& out, size_t num_pixels,
+                          bool alpha_is_premultiplied, bool clamp) {
+  if (alpha_is_premultiplied) {
+    for (size_t x = 0; x < num_pixels; ++x) {
+      float fga = clamp ? Clamp(fg.a[x]) : fg.a[x];
+      out.r[x] = (fg.r[x] + bg.r[x] * (1.f - fga));
+      out.g[x] = (fg.g[x] + bg.g[x] * (1.f - fga));
+      out.b[x] = (fg.b[x] + bg.b[x] * (1.f - fga));
+      out.a[x] = (1.f - (1.f - fga) * (1.f - bg.a[x]));
+    }
+  } else {
+    for (size_t x = 0; x < num_pixels; ++x) {
+      float fga = clamp ? Clamp(fg.a[x]) : fg.a[x];
+      const float new_a = 1.f - (1.f - fga) * (1.f - bg.a[x]);
+      const float rnew_a = (new_a > 0 ? 1.f / new_a : 0.f);
+      out.r[x] = (fg.r[x] * fga + bg.r[x] * bg.a[x] * (1.f - fga)) * rnew_a;
+      out.g[x] = (fg.g[x] * fga + bg.g[x] * bg.a[x] * (1.f - fga)) * rnew_a;
+      out.b[x] = (fg.b[x] * fga + bg.b[x] * bg.a[x] * (1.f - fga)) * rnew_a;
+      out.a[x] = new_a;
+    }
+  }
+}
+void PerformAlphaBlending(const float* bg, const float* bga, const float* fg,
+                          const float* fga, float* out, size_t num_pixels,
+                          bool alpha_is_premultiplied, bool clamp) {
+  if (bg == bga && fg == fga) {
+    for (size_t x = 0; x < num_pixels; ++x) {
+      float fa = clamp ? fga[x] : Clamp(fga[x]);
+      out[x] = (1.f - (1.f - fa) * (1.f - bga[x]));
+    }
+  } else {
+    if (alpha_is_premultiplied) {
+      for (size_t x = 0; x < num_pixels; ++x) {
+        float fa = clamp ? fga[x] : Clamp(fga[x]);
+        out[x] = (fg[x] + bg[x] * (1.f - fa));
+      }
+    } else {
+      for (size_t x = 0; x < num_pixels; ++x) {
+        float fa = clamp ? fga[x] : Clamp(fga[x]);
+        const float new_a = 1.f - (1.f - fa) * (1.f - bga[x]);
+        const float rnew_a = (new_a > 0 ? 1.f / new_a : 0.f);
+        out[x] = (fg[x] * fa + bg[x] * bga[x] * (1.f - fa)) * rnew_a;
+      }
+    }
+  }
+}
+
+void PerformAlphaWeightedAdd(const float* bg, const float* fg, const float* fga,
+                             float* out, size_t num_pixels, bool clamp) {
+  if (fg == fga) {
+    memcpy(out, bg, num_pixels * sizeof(*out));
+  } else if (clamp) {
+    for (size_t x = 0; x < num_pixels; ++x) {
+      out[x] = bg[x] + fg[x] * Clamp(fga[x]);
+    }
+  } else {
+    for (size_t x = 0; x < num_pixels; ++x) {
+      out[x] = bg[x] + fg[x] * fga[x];
+    }
+  }
+}
+
+void PerformMulBlending(const float* bg, const float* fg, float* out,
+                        size_t num_pixels, bool clamp) {
+  if (clamp) {
+    for (size_t x = 0; x < num_pixels; ++x) {
+      out[x] = bg[x] * Clamp(fg[x]);
+    }
+  } else {
+    for (size_t x = 0; x < num_pixels; ++x) {
+      out[x] = bg[x] * fg[x];
+    }
+  }
+}
+
+void PremultiplyAlpha(float* JXL_RESTRICT r, float* JXL_RESTRICT g,
+                      float* JXL_RESTRICT b, const float* JXL_RESTRICT a,
+                      size_t num_pixels) {
+  for (size_t x = 0; x < num_pixels; ++x) {
+    const float multiplier = std::max(kSmallAlpha, a[x]);
+    r[x] *= multiplier;
+    g[x] *= multiplier;
+    b[x] *= multiplier;
+  }
+}
+
+void UnpremultiplyAlpha(float* JXL_RESTRICT r, float* JXL_RESTRICT g,
+                        float* JXL_RESTRICT b, const float* JXL_RESTRICT a,
+                        size_t num_pixels) {
+  for (size_t x = 0; x < num_pixels; ++x) {
+    const float multiplier = 1.f / std::max(kSmallAlpha, a[x]);
+    r[x] *= multiplier;
+    g[x] *= multiplier;
+    b[x] *= multiplier;
+  }
+}
+
+}  // namespace jxl