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Side by Side Diff: remoting/host/differ.cc

Issue 11470028: Move screen capturers to remoting/capturer. (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Created 8 years ago
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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "remoting/host/differ.h"
6
7 #include "base/logging.h"
8 #include "remoting/host/differ_block.h"
9
10 namespace remoting {
11
12 Differ::Differ(int width, int height, int bpp, int stride) {
13 // Dimensions of screen.
14 width_ = width;
15 height_ = height;
16 bytes_per_pixel_ = bpp;
17 bytes_per_row_ = stride;
18
19 // Calc number of blocks (full and partial) required to cover entire image.
20 // One additional row/column is added as a boundary on the right & bottom.
21 diff_info_width_ = ((width_ + kBlockSize - 1) / kBlockSize) + 1;
22 diff_info_height_ = ((height_ + kBlockSize - 1) / kBlockSize) + 1;
23 diff_info_size_ = diff_info_width_ * diff_info_height_ * sizeof(DiffInfo);
24 diff_info_.reset(new DiffInfo[diff_info_size_]);
25 }
26
27 Differ::~Differ() {}
28
29 void Differ::CalcDirtyRegion(const void* prev_buffer, const void* curr_buffer,
30 SkRegion* region) {
31 if (!region) {
32 return;
33 }
34 region->setEmpty();
35
36 if (!prev_buffer || !curr_buffer) {
37 return;
38 }
39
40 // Identify all the blocks that contain changed pixels.
41 MarkDirtyBlocks(prev_buffer, curr_buffer);
42
43 // Now that we've identified the blocks that have changed, merge adjacent
44 // blocks to minimize the number of rects that we return.
45 MergeBlocks(region);
46 }
47
48 void Differ::MarkDirtyBlocks(const void* prev_buffer, const void* curr_buffer) {
49 memset(diff_info_.get(), 0, diff_info_size_);
50
51 // Calc number of full blocks.
52 int x_full_blocks = width_ / kBlockSize;
53 int y_full_blocks = height_ / kBlockSize;
54
55 // Calc size of partial blocks which may be present on right and bottom edge.
56 int partial_column_width = width_ - (x_full_blocks * kBlockSize);
57 int partial_row_height = height_ - (y_full_blocks * kBlockSize);
58
59 // Offset from the start of one block-column to the next.
60 int block_x_offset = bytes_per_pixel_ * kBlockSize;
61 // Offset from the start of one block-row to the next.
62 int block_y_stride = (width_ * bytes_per_pixel_) * kBlockSize;
63 // Offset from the start of one diff_info row to the next.
64 int diff_info_stride = diff_info_width_ * sizeof(DiffInfo);
65
66 const uint8* prev_block_row_start = static_cast<const uint8*>(prev_buffer);
67 const uint8* curr_block_row_start = static_cast<const uint8*>(curr_buffer);
68 DiffInfo* diff_info_row_start = static_cast<DiffInfo*>(diff_info_.get());
69
70 for (int y = 0; y < y_full_blocks; y++) {
71 const uint8* prev_block = prev_block_row_start;
72 const uint8* curr_block = curr_block_row_start;
73 DiffInfo* diff_info = diff_info_row_start;
74
75 for (int x = 0; x < x_full_blocks; x++) {
76 // Mark this block as being modified so that it gets incorporated into
77 // a dirty rect.
78 *diff_info = BlockDifference(prev_block, curr_block, bytes_per_row_);
79 prev_block += block_x_offset;
80 curr_block += block_x_offset;
81 diff_info += sizeof(DiffInfo);
82 }
83
84 // If there is a partial column at the end, handle it.
85 // This condition should rarely, if ever, occur.
86 if (partial_column_width != 0) {
87 *diff_info = DiffPartialBlock(prev_block, curr_block, bytes_per_row_,
88 partial_column_width, kBlockSize);
89 diff_info += sizeof(DiffInfo);
90 }
91
92 // Update pointers for next row.
93 prev_block_row_start += block_y_stride;
94 curr_block_row_start += block_y_stride;
95 diff_info_row_start += diff_info_stride;
96 }
97
98 // If the screen height is not a multiple of the block size, then this
99 // handles the last partial row. This situation is far more common than the
100 // 'partial column' case.
101 if (partial_row_height != 0) {
102 const uint8* prev_block = prev_block_row_start;
103 const uint8* curr_block = curr_block_row_start;
104 DiffInfo* diff_info = diff_info_row_start;
105 for (int x = 0; x < x_full_blocks; x++) {
106 *diff_info = DiffPartialBlock(prev_block, curr_block,
107 bytes_per_row_,
108 kBlockSize, partial_row_height);
109 prev_block += block_x_offset;
110 curr_block += block_x_offset;
111 diff_info += sizeof(DiffInfo);
112 }
113 if (partial_column_width != 0) {
114 *diff_info = DiffPartialBlock(prev_block, curr_block, bytes_per_row_,
115 partial_column_width, partial_row_height);
116 diff_info += sizeof(DiffInfo);
117 }
118 }
119 }
120
121 DiffInfo Differ::DiffPartialBlock(const uint8* prev_buffer,
122 const uint8* curr_buffer,
123 int stride, int width, int height) {
124 int width_bytes = width * bytes_per_pixel_;
125 for (int y = 0; y < height; y++) {
126 if (memcmp(prev_buffer, curr_buffer, width_bytes) != 0)
127 return 1;
128 prev_buffer += bytes_per_row_;
129 curr_buffer += bytes_per_row_;
130 }
131 return 0;
132 }
133
134 void Differ::MergeBlocks(SkRegion* region) {
135 DCHECK(region);
136 region->setEmpty();
137
138 uint8* diff_info_row_start = static_cast<uint8*>(diff_info_.get());
139 int diff_info_stride = diff_info_width_ * sizeof(DiffInfo);
140
141 for (int y = 0; y < diff_info_height_; y++) {
142 uint8* diff_info = diff_info_row_start;
143 for (int x = 0; x < diff_info_width_; x++) {
144 if (*diff_info != 0) {
145 // We've found a modified block. Look at blocks to the right and below
146 // to group this block with as many others as we can.
147 int left = x * kBlockSize;
148 int top = y * kBlockSize;
149 int width = 1;
150 int height = 1;
151 *diff_info = 0;
152
153 // Group with blocks to the right.
154 // We can keep looking until we find an unchanged block because we
155 // have a boundary block which is never marked as having diffs.
156 uint8* right = diff_info + 1;
157 while (*right) {
158 *right++ = 0;
159 width++;
160 }
161
162 // Group with blocks below.
163 // The entire width of blocks that we matched above much match for
164 // each row that we add.
165 uint8* bottom = diff_info;
166 bool found_new_row;
167 do {
168 found_new_row = true;
169 bottom += diff_info_stride;
170 right = bottom;
171 for (int x2 = 0; x2 < width; x2++) {
172 if (*right++ == 0) {
173 found_new_row = false;
174 }
175 }
176
177 if (found_new_row) {
178 height++;
179
180 // We need to go back and erase the diff markers so that we don't
181 // try to add these blocks a second time.
182 right = bottom;
183 for (int x2 = 0; x2 < width; x2++) {
184 *right++ = 0;
185 }
186 }
187 } while (found_new_row);
188
189 // Add rect to list of dirty rects.
190 width *= kBlockSize;
191 if (left + width > width_) {
192 width = width_ - left;
193 }
194 height *= kBlockSize;
195 if (top + height > height_) {
196 height = height_ - top;
197 }
198 region->op(SkIRect::MakeXYWH(left, top, width, height),
199 SkRegion::kUnion_Op);
200 }
201
202 // Increment to next block in this row.
203 diff_info++;
204 }
205
206 // Go to start of next row.
207 diff_info_row_start += diff_info_stride;
208 }
209 }
210
211 } // namespace remoting
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