Revised sub-rectangle scaling for use in Chromoting.

remoting/base/decoder_vp8.cc

Index: remoting/base/decoder_vp8.cc
diff --git a/remoting/base/decoder_vp8.cc b/remoting/base/decoder_vp8.cc
index 6ce7f0358988aeeedcfa888783aa30f4c315350b..651301506c977deada709e82120140038e8e67a6 100644
--- a/remoting/base/decoder_vp8.cc
+++ b/remoting/base/decoder_vp8.cc
@@ -4,6 +4,8 @@
 
 #include "remoting/base/decoder_vp8.h"
 
+#include <math.h>
+
 #include "base/logging.h"
 #include "media/base/media.h"
 #include "media/base/yuv_convert.h"
@@ -154,82 +156,96 @@ bool DecoderVp8::DoScaling() const {
   return horizontal_scale_ratio_ != 1.0 || vertical_scale_ratio_ != 1.0;
 }
 
-void DecoderVp8::ConvertRects(const RectVector& rects,
+void DecoderVp8::ConvertRects(const RectVector& input_rects,
                               RectVector* output_rects) {
   if (!last_image_)
     return;
 
-  uint8* data_start = frame_->data(media::VideoFrame::kRGBPlane);
-  const int stride = frame_->stride(media::VideoFrame::kRGBPlane);
+  // The conversion routine we use is optimized for even widths & heights.
+  int image_width = RoundToTwosMultiple(last_image_->d_w);
+  int image_height = RoundToTwosMultiple(last_image_->d_h);
+
+  uint8* output_rgb_buf = frame_->data(media::VideoFrame::kRGBPlane);
+  const int output_stride = frame_->stride(media::VideoFrame::kRGBPlane);
 
   output_rects->clear();
-  output_rects->reserve(rects.size());
-  for (size_t i = 0; i < rects.size(); ++i) {
-    // Clip by the clipping rectangle first.
-    SkIRect dest_rect = rects[i];
-    if (!dest_rect.intersect(clip_rect_))
-      continue;
 
-    // Round down the image width and height.
-    int image_width = RoundToTwosMultiple(last_image_->d_w);
-    int image_height = RoundToTwosMultiple(last_image_->d_h);
+  // Clip based on both the output dimensions and Pepper clip rect.
+  SkIRect clip_rect = clip_rect_;
+  if (!clip_rect.intersect(SkIRect::MakeWH(image_width, image_height)))
+    return;
 
-    // Then clip by the rounded down dimension of the image for safety.
-    if (!dest_rect.intersect(SkIRect::MakeWH(image_width, image_height)))
-      continue;
+  output_rects->reserve(input_rects.size());
 
+  for (size_t i = 0; i < input_rects.size(); ++i) {
     // Align the rectangle to avoid artifacts in color space conversion.
-    dest_rect = AlignRect(dest_rect);
+    SkIRect dest_rect = AlignRect(input_rects[i]);
+
+    // Clip to the image and Pepper clip region.
+    if (!dest_rect.intersect(clip_rect))
+      continue;
 
     ConvertYUVToRGB32WithRect(last_image_->planes[0],
                               last_image_->planes[1],
                               last_image_->planes[2],
-                              data_start,
+                              output_rgb_buf,
                               dest_rect,
                               last_image_->stride[0],
                               last_image_->stride[1],
-                              stride);
+                              output_stride);
+
     output_rects->push_back(dest_rect);
   }
 }
 
-void DecoderVp8::ScaleAndConvertRects(const RectVector& rects,
+void DecoderVp8::ScaleAndConvertRects(const RectVector& input_rects,
                                       RectVector* output_rects) {
   if (!last_image_)
     return;
 
-  uint8* data_start = frame_->data(media::VideoFrame::kRGBPlane);
-  const int stride = frame_->stride(media::VideoFrame::kRGBPlane);
+  int input_width = last_image_->d_w;
+  int input_height = last_image_->d_h;
+
+  uint8* output_rgb_buf = frame_->data(media::VideoFrame::kRGBPlane);
+  const int output_stride = frame_->stride(media::VideoFrame::kRGBPlane);
+
+  // TODO(wez): Resize |frame_| to our desired output dimensions when scaling.
+  int output_width = ceil(input_width * horizontal_scale_ratio_);
+  int output_height = ceil(input_height * vertical_scale_ratio_);
 
   output_rects->clear();
-  output_rects->reserve(rects.size());
-  for (size_t i = 0; i < rects.size(); ++i) {
-    // Round down the image width and height.
-    int image_width = RoundToTwosMultiple(last_image_->d_w);
-    int image_height = RoundToTwosMultiple(last_image_->d_h);
-
-    // Clip by the rounded down dimension of the image for safety.
-    SkIRect dest_rect = rects[i];
-    if (!dest_rect.intersect(SkIRect::MakeWH(image_width, image_height)))
-      continue;
 
-    // Align the rectangle to avoid artifacts in color space conversion.
-    dest_rect = AlignRect(dest_rect);
+  // Clip based on both the output dimensions and Pepper clip rect.
+  SkIRect clip_rect = clip_rect_;
+  if (!clip_rect.intersect(SkIRect::MakeWH(output_width, output_height)))
+    return;
+
+  output_rects->reserve(input_rects.size());
 
-    SkIRect scaled_rect = ScaleRect(dest_rect,
+  for (size_t i = 0; i < input_rects.size(); ++i) {
+    // Determine the scaled area affected by this rectangle changing.
+    SkIRect output_rect = ScaleRect(input_rects[i],
                                     horizontal_scale_ratio_,
                                     vertical_scale_ratio_);
+    if (!output_rect.intersect(clip_rect))
+      continue;
 
-    ScaleYUVToRGB32WithRect(last_image_->planes[0],
-                            last_image_->planes[1],
-                            last_image_->planes[2],
-                            data_start,
-                            dest_rect,
-                            scaled_rect,
-                            last_image_->stride[0],
-                            last_image_->stride[1],
-                            stride);
-    output_rects->push_back(scaled_rect);
+    // The scaler will not to read outside the input dimensions.
+    media::ScaleYUVToRGB32WithRect(last_image_->planes[0],
+                                   last_image_->planes[1],
+                                   last_image_->planes[2],
+                                   output_rgb_buf,
+                                   input_width,
+                                   input_height,
+                                   output_width, output_height,
+                                   output_rect.x(),
+                                   output_rect.y(),
+                                   output_rect.right(),
+                                   output_rect.bottom(),
+                                   last_image_->stride[0],
+                                   last_image_->stride[1],
+                                   output_stride);
+    output_rects->push_back(output_rect);
   }
 }