1 files changed, 152 insertions, 0 deletions
diff --git a/media/libjxl/src/lib/jxl/blending.cc b/media/libjxl/src/lib/jxl/blending.cc
new file mode 100644
index 0000000000..ab37fdabb5
--- /dev/null
+++ b/media/libjxl/src/lib/jxl/blending.cc
@@ -0,0 +1,152 @@
+// 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/blending.h"
+
+#include "lib/jxl/alpha.h"
+#include "lib/jxl/image_ops.h"
+
+namespace jxl {
+
+bool NeedsBlending(PassesDecoderState* dec_state) {
+  const PassesSharedState& state = *dec_state->shared;
+  if (!(state.frame_header.frame_type == FrameType::kRegularFrame ||
+        state.frame_header.frame_type == FrameType::kSkipProgressive)) {
+    return false;
+  }
+  const auto& info = state.frame_header.blending_info;
+  bool replace_all = (info.mode == BlendMode::kReplace);
+  for (const auto& ec_i : state.frame_header.extra_channel_blending_info) {
+    if (ec_i.mode != BlendMode::kReplace) {
+      replace_all = false;
+    }
+  }
+  // Replace the full frame: nothing to do.
+  if (!state.frame_header.custom_size_or_origin && replace_all) {
+    return false;
+  }
+  return true;
+}
+
+void PerformBlending(const float* const* bg, const float* const* fg,
+                     float* const* out, size_t x0, size_t xsize,
+                     const PatchBlending& color_blending,
+                     const PatchBlending* ec_blending,
+                     const std::vector<ExtraChannelInfo>& extra_channel_info) {
+  bool has_alpha = false;
+  size_t num_ec = extra_channel_info.size();
+  for (size_t i = 0; i < num_ec; i++) {
+    if (extra_channel_info[i].type == jxl::ExtraChannel::kAlpha) {
+      has_alpha = true;
+      break;
+    }
+  }
+  ImageF tmp(xsize, 3 + num_ec);
+  // Blend extra channels first so that we use the pre-blending alpha.
+  for (size_t i = 0; i < num_ec; i++) {
+    if (ec_blending[i].mode == PatchBlendMode::kAdd) {
+      for (size_t x = 0; x < xsize; x++) {
+        tmp.Row(3 + i)[x] = bg[3 + i][x + x0] + fg[3 + i][x + x0];
+      }
+    } else if (ec_blending[i].mode == PatchBlendMode::kBlendAbove) {
+      size_t alpha = ec_blending[i].alpha_channel;
+      bool is_premultiplied = extra_channel_info[alpha].alpha_associated;
+      PerformAlphaBlending(bg[3 + i] + x0, bg[3 + alpha] + x0, fg[3 + i] + x0,
+                           fg[3 + alpha] + x0, tmp.Row(3 + i), xsize,
+                           is_premultiplied, ec_blending[i].clamp);
+    } else if (ec_blending[i].mode == PatchBlendMode::kBlendBelow) {
+      size_t alpha = ec_blending[i].alpha_channel;
+      bool is_premultiplied = extra_channel_info[alpha].alpha_associated;
+      PerformAlphaBlending(fg[3 + i] + x0, fg[3 + alpha] + x0, bg[3 + i] + x0,
+                           bg[3 + alpha] + x0, tmp.Row(3 + i), xsize,
+                           is_premultiplied, ec_blending[i].clamp);
+    } else if (ec_blending[i].mode == PatchBlendMode::kAlphaWeightedAddAbove) {
+      size_t alpha = ec_blending[i].alpha_channel;
+      PerformAlphaWeightedAdd(bg[3 + i] + x0, fg[3 + i] + x0,
+                              fg[3 + alpha] + x0, tmp.Row(3 + i), xsize,
+                              ec_blending[i].clamp);
+    } else if (ec_blending[i].mode == PatchBlendMode::kAlphaWeightedAddBelow) {
+      size_t alpha = ec_blending[i].alpha_channel;
+      PerformAlphaWeightedAdd(fg[3 + i] + x0, bg[3 + i] + x0,
+                              bg[3 + alpha] + x0, tmp.Row(3 + i), xsize,
+                              ec_blending[i].clamp);
+    } else if (ec_blending[i].mode == PatchBlendMode::kMul) {
+      PerformMulBlending(bg[3 + i] + x0, fg[3 + i] + x0, tmp.Row(3 + i), xsize,
+                         ec_blending[i].clamp);
+    } else if (ec_blending[i].mode == PatchBlendMode::kReplace) {
+      memcpy(tmp.Row(3 + i), fg[3 + i] + x0, xsize * sizeof(**fg));
+    } else if (ec_blending[i].mode == PatchBlendMode::kNone) {
+      if (xsize) memcpy(tmp.Row(3 + i), bg[3 + i] + x0, xsize * sizeof(**fg));
+    } else {
+      JXL_ABORT("Unreachable");
+    }
+  }
+  size_t alpha = color_blending.alpha_channel;
+
+  if (color_blending.mode == PatchBlendMode::kAdd ||
+      (color_blending.mode == PatchBlendMode::kAlphaWeightedAddAbove &&
+       !has_alpha) ||
+      (color_blending.mode == PatchBlendMode::kAlphaWeightedAddBelow &&
+       !has_alpha)) {
+    for (int p = 0; p < 3; p++) {
+      float* out = tmp.Row(p);
+      for (size_t x = 0; x < xsize; x++) {
+        out[x] = bg[p][x + x0] + fg[p][x + x0];
+      }
+    }
+  } else if (color_blending.mode == PatchBlendMode::kBlendAbove
+             // blend without alpha is just replace
+             && has_alpha) {
+    bool is_premultiplied = extra_channel_info[alpha].alpha_associated;
+    PerformAlphaBlending(
+        {bg[0] + x0, bg[1] + x0, bg[2] + x0, bg[3 + alpha] + x0},
+        {fg[0] + x0, fg[1] + x0, fg[2] + x0, fg[3 + alpha] + x0},
+        {tmp.Row(0), tmp.Row(1), tmp.Row(2), tmp.Row(3 + alpha)}, xsize,
+        is_premultiplied, color_blending.clamp);
+  } else if (color_blending.mode == PatchBlendMode::kBlendBelow
+             // blend without alpha is just replace
+             && has_alpha) {
+    bool is_premultiplied = extra_channel_info[alpha].alpha_associated;
+    PerformAlphaBlending(
+        {fg[0] + x0, fg[1] + x0, fg[2] + x0, fg[3 + alpha] + x0},
+        {bg[0] + x0, bg[1] + x0, bg[2] + x0, bg[3 + alpha] + x0},
+        {tmp.Row(0), tmp.Row(1), tmp.Row(2), tmp.Row(3 + alpha)}, xsize,
+        is_premultiplied, color_blending.clamp);
+  } else if (color_blending.mode == PatchBlendMode::kAlphaWeightedAddAbove) {
+    JXL_DASSERT(has_alpha);
+    for (size_t c = 0; c < 3; c++) {
+      PerformAlphaWeightedAdd(bg[c] + x0, fg[c] + x0, fg[3 + alpha] + x0,
+                              tmp.Row(c), xsize, color_blending.clamp);
+    }
+  } else if (color_blending.mode == PatchBlendMode::kAlphaWeightedAddBelow) {
+    JXL_DASSERT(has_alpha);
+    for (size_t c = 0; c < 3; c++) {
+      PerformAlphaWeightedAdd(fg[c] + x0, bg[c] + x0, bg[3 + alpha] + x0,
+                              tmp.Row(c), xsize, color_blending.clamp);
+    }
+  } else if (color_blending.mode == PatchBlendMode::kMul) {
+    for (int p = 0; p < 3; p++) {
+      PerformMulBlending(bg[p] + x0, fg[p] + x0, tmp.Row(p), xsize,
+                         color_blending.clamp);
+    }
+  } else if (color_blending.mode == PatchBlendMode::kReplace ||
+             color_blending.mode == PatchBlendMode::kBlendAbove ||
+             color_blending.mode == PatchBlendMode::kBlendBelow) {  // kReplace
+    for (size_t p = 0; p < 3; p++) {
+      memcpy(tmp.Row(p), fg[p] + x0, xsize * sizeof(**fg));
+    }
+  } else if (color_blending.mode == PatchBlendMode::kNone) {
+    for (size_t p = 0; p < 3; p++) {
+      memcpy(tmp.Row(p), bg[p] + x0, xsize * sizeof(**fg));
+    }
+  } else {
+    JXL_ABORT("Unreachable");
+  }
+  for (size_t i = 0; i < 3 + num_ec; i++) {
+    if (xsize != 0) memcpy(out[i] + x0, tmp.Row(i), xsize * sizeof(**out));
+  }
+}
+
+}  // namespace jxl