1 files changed, 251 insertions, 0 deletions
diff --git a/gfx/2d/ImageScaling.cpp b/gfx/2d/ImageScaling.cpp
new file mode 100644
index 000000000..190b7a7b9
--- /dev/null
+++ b/gfx/2d/ImageScaling.cpp
@@ -0,0 +1,251 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ImageScaling.h"
+#include "2D.h"
+#include "DataSurfaceHelpers.h"
+
+#include <math.h>
+#include <algorithm>
+
+using namespace std;
+
+namespace mozilla {
+namespace gfx {
+
+inline uint32_t Avg2x2(uint32_t a, uint32_t b, uint32_t c, uint32_t d)
+{
+  // Prepare half-adder work
+  uint32_t sum = a ^ b ^ c;
+  uint32_t carry = (a & b) | (a & c) | (b & c);
+
+  // Before shifting, mask lower order bits of each byte to avoid underflow.
+  uint32_t mask = 0xfefefefe;
+
+  // Add d to sum and divide by 2.
+  sum = (((sum ^ d) & mask) >> 1) + (sum & d);
+
+  // Sum is now shifted into place relative to carry, add them together.
+  return (((sum ^ carry) & mask) >> 1) + (sum & carry);
+}
+
+inline uint32_t Avg2(uint32_t a, uint32_t b)
+{
+  // Prepare half-adder work
+  uint32_t sum = a ^ b;
+  uint32_t carry = (a & b);
+
+  // Before shifting, mask lower order bits of each byte to avoid underflow.
+  uint32_t mask = 0xfefefefe;
+
+  // Add d to sum and divide by 2.
+  return ((sum & mask) >> 1) + carry;
+}
+
+void
+ImageHalfScaler::ScaleForSize(const IntSize &aSize)
+{
+  uint32_t horizontalDownscales = 0;
+  uint32_t verticalDownscales = 0;
+
+  IntSize scaleSize = mOrigSize;
+  while ((scaleSize.height / 2) > aSize.height) {
+    verticalDownscales++;
+    scaleSize.height /= 2;
+  }
+
+  while ((scaleSize.width / 2) > aSize.width) {
+    horizontalDownscales++;
+    scaleSize.width /= 2;
+  }
+
+  if (scaleSize == mOrigSize) {
+    return;
+  }
+
+  delete [] mDataStorage;
+
+  IntSize internalSurfSize;
+  internalSurfSize.width = max(scaleSize.width, mOrigSize.width / 2);
+  internalSurfSize.height = max(scaleSize.height, mOrigSize.height / 2);
+
+  size_t bufLen = 0;
+  mStride = GetAlignedStride<16>(internalSurfSize.width, 4);
+  if (mStride > 0) {
+    // Allocate 15 bytes extra to make sure we can get 16 byte alignment. We
+    // should add tools for this, see bug 751696.
+    bufLen = BufferSizeFromStrideAndHeight(mStride, internalSurfSize.height, 15);
+  }
+
+  if (bufLen == 0) {
+    mSize.SizeTo(0, 0);
+    mDataStorage = nullptr;
+    return;
+  }
+  mDataStorage = new uint8_t[bufLen];
+
+  if (uintptr_t(mDataStorage) % 16) {
+    // Our storage does not start at a 16-byte boundary. Make sure mData does!
+    mData = (uint8_t*)(uintptr_t(mDataStorage) +
+      (16 - (uintptr_t(mDataStorage) % 16)));
+  } else {
+    mData = mDataStorage;
+  }
+
+  mSize = scaleSize;
+
+  /* The surface we sample from might not be even sized, if it's not we will
+   * ignore the last row/column. This means we lose some data but it keeps the
+   * code very simple. There's also no perfect answer that provides a better
+   * solution.
+   */
+  IntSize currentSampledSize = mOrigSize;
+  uint32_t currentSampledStride = mOrigStride;
+  uint8_t *currentSampledData = mOrigData;
+  
+  while (verticalDownscales && horizontalDownscales) {
+    if (currentSampledSize.width % 2) {
+      currentSampledSize.width -= 1;
+    }
+    if (currentSampledSize.height % 2) {
+      currentSampledSize.height -= 1;
+    }
+
+    HalfImage2D(currentSampledData, currentSampledStride, currentSampledSize,
+                mData, mStride);
+
+    verticalDownscales--;
+    horizontalDownscales--;
+    currentSampledSize.width /= 2;
+    currentSampledSize.height /= 2;
+    currentSampledData = mData;
+    currentSampledStride = mStride;
+  }
+
+  while (verticalDownscales) {
+    if (currentSampledSize.height % 2) {
+      currentSampledSize.height -= 1;
+    }
+
+    HalfImageVertical(currentSampledData, currentSampledStride, currentSampledSize,
+                      mData, mStride);
+
+    verticalDownscales--;
+    currentSampledSize.height /= 2;
+    currentSampledData = mData;
+    currentSampledStride = mStride;
+  }
+
+
+  while (horizontalDownscales) {
+    if (currentSampledSize.width % 2) {
+      currentSampledSize.width -= 1;
+    }
+
+    HalfImageHorizontal(currentSampledData, currentSampledStride, currentSampledSize,
+                        mData, mStride);
+
+    horizontalDownscales--;
+    currentSampledSize.width /= 2;
+    currentSampledData = mData;
+    currentSampledStride = mStride;
+  }
+}
+
+void
+ImageHalfScaler::HalfImage2D(uint8_t *aSource, int32_t aSourceStride,
+                             const IntSize &aSourceSize, uint8_t *aDest,
+                             uint32_t aDestStride)
+{
+#ifdef USE_SSE2
+  if (Factory::HasSSE2()) {
+    HalfImage2D_SSE2(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
+  } else
+#endif
+  {
+    HalfImage2D_C(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
+  }
+}
+
+void
+ImageHalfScaler::HalfImageVertical(uint8_t *aSource, int32_t aSourceStride,
+                                   const IntSize &aSourceSize, uint8_t *aDest,
+                                   uint32_t aDestStride)
+{
+#ifdef USE_SSE2
+  if (Factory::HasSSE2()) {
+    HalfImageVertical_SSE2(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
+  } else
+#endif
+  {
+    HalfImageVertical_C(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
+  }
+}
+
+void
+ImageHalfScaler::HalfImageHorizontal(uint8_t *aSource, int32_t aSourceStride,
+                                     const IntSize &aSourceSize, uint8_t *aDest,
+                                     uint32_t aDestStride)
+{
+#ifdef USE_SSE2
+  if (Factory::HasSSE2()) {
+    HalfImageHorizontal_SSE2(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
+  } else
+#endif
+  {
+    HalfImageHorizontal_C(aSource, aSourceStride, aSourceSize, aDest, aDestStride);
+  }
+}
+
+void
+ImageHalfScaler::HalfImage2D_C(uint8_t *aSource, int32_t aSourceStride,
+                               const IntSize &aSourceSize, uint8_t *aDest,
+                               uint32_t aDestStride)
+{
+  for (int y = 0; y < aSourceSize.height; y += 2) {
+    uint32_t *storage = (uint32_t*)(aDest + (y / 2) * aDestStride);
+    for (int x = 0; x < aSourceSize.width; x += 2) {
+      uint8_t *upperRow = aSource + (y * aSourceStride + x * 4);
+      uint8_t *lowerRow = aSource + ((y + 1) * aSourceStride + x * 4);
+
+      *storage++ = Avg2x2(*(uint32_t*)upperRow, *((uint32_t*)upperRow + 1),
+                          *(uint32_t*)lowerRow, *((uint32_t*)lowerRow + 1));
+    }
+  }
+}
+
+void
+ImageHalfScaler::HalfImageVertical_C(uint8_t *aSource, int32_t aSourceStride,
+                                     const IntSize &aSourceSize, uint8_t *aDest,
+                                     uint32_t aDestStride)
+{
+  for (int y = 0; y < aSourceSize.height; y += 2) {
+    uint32_t *storage = (uint32_t*)(aDest + (y / 2) * aDestStride);
+    for (int x = 0; x < aSourceSize.width; x++) {
+      uint32_t *upperRow = (uint32_t*)(aSource + (y * aSourceStride + x * 4));
+      uint32_t *lowerRow = (uint32_t*)(aSource + ((y + 1) * aSourceStride + x * 4));
+
+      *storage++ = Avg2(*upperRow, *lowerRow);
+    }
+  }
+}
+
+void
+ImageHalfScaler::HalfImageHorizontal_C(uint8_t *aSource, int32_t aSourceStride,
+                                       const IntSize &aSourceSize, uint8_t *aDest,
+                                       uint32_t aDestStride)
+{
+  for (int y = 0; y < aSourceSize.height; y++) {
+    uint32_t *storage = (uint32_t*)(aDest + y * aDestStride);
+    for (int x = 0; x < aSourceSize.width;  x+= 2) {
+      uint32_t *pixels = (uint32_t*)(aSource + (y * aSourceStride + x * 4));
+
+      *storage++ = Avg2(*pixels, *(pixels + 1));
+    }
+  }
+}
+
+} // namespace gfx
+} // namespace mozilla