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1 : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 : /* This Source Code Form is subject to the terms of the Mozilla Public
4 : * License, v. 2.0. If a copy of the MPL was not distributed with this
5 : * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 :
7 : /**
8 : * DownscalingSurfaceFilter is a SurfaceFilter implementation for use with
9 : * SurfacePipe which performs Lanczos downscaling.
10 : *
11 : * It's in this header file, separated from the other SurfaceFilters, because
12 : * some preprocessor magic is necessary to ensure that there aren't compilation
13 : * issues on platforms where Skia is unavailable.
14 : */
15 :
16 : #ifndef mozilla_image_DownscalingFilter_h
17 : #define mozilla_image_DownscalingFilter_h
18 :
19 : #include <algorithm>
20 : #include <ctime>
21 : #include <stdint.h>
22 :
23 : #include "mozilla/Maybe.h"
24 : #include "mozilla/UniquePtr.h"
25 : #include "mozilla/gfx/2D.h"
26 : #include "gfxPrefs.h"
27 :
28 : #ifdef MOZ_ENABLE_SKIA
29 : #include "mozilla/gfx/ConvolutionFilter.h"
30 : #endif
31 :
32 : #include "SurfacePipe.h"
33 :
34 : namespace mozilla {
35 : namespace image {
36 :
37 : //////////////////////////////////////////////////////////////////////////////
38 : // DownscalingFilter
39 : //////////////////////////////////////////////////////////////////////////////
40 :
41 : template <typename Next> class DownscalingFilter;
42 :
43 : /**
44 : * A configuration struct for DownscalingConfig.
45 : */
46 : struct DownscalingConfig
47 : {
48 : template <typename Next> using Filter = DownscalingFilter<Next>;
49 : gfx::IntSize mInputSize; /// The size of the input image. We'll downscale
50 : /// from this size to the input size of the next
51 : /// SurfaceFilter in the chain.
52 : gfx::SurfaceFormat mFormat; /// The pixel format - BGRA or BGRX. (BGRX has
53 : /// slightly better performance.)
54 : };
55 :
56 : #ifndef MOZ_ENABLE_SKIA
57 :
58 : /**
59 : * DownscalingFilter requires Skia. This is a fallback implementation for
60 : * non-Skia builds that fails when Configure() is called (which will prevent
61 : * SurfacePipeFactory from returning an instance of it) and crashes if a caller
62 : * manually constructs an instance and attempts to actually use it. Callers
63 : * should avoid this by ensuring that they do not request downscaling in
64 : * non-Skia builds.
65 : */
66 : template <typename Next>
67 : class DownscalingFilter final : public SurfaceFilter
68 : {
69 : public:
70 : Maybe<SurfaceInvalidRect> TakeInvalidRect() override { return Nothing(); }
71 :
72 : template <typename... Rest>
73 : nsresult Configure(const DownscalingConfig& aConfig, Rest... aRest)
74 : {
75 : return NS_ERROR_FAILURE;
76 : }
77 :
78 : protected:
79 : uint8_t* DoResetToFirstRow() override { MOZ_CRASH(); return nullptr; }
80 : uint8_t* DoAdvanceRow() override { MOZ_CRASH(); return nullptr; }
81 : };
82 :
83 : #else
84 :
85 : /**
86 : * DownscalingFilter performs Lanczos downscaling, taking image input data at one size
87 : * and outputting it rescaled to a different size.
88 : *
89 : * The 'Next' template parameter specifies the next filter in the chain.
90 : */
91 : template <typename Next>
92 : class DownscalingFilter final : public SurfaceFilter
93 : {
94 : public:
95 0 : DownscalingFilter()
96 : : mWindowCapacity(0)
97 : , mRowsInWindow(0)
98 : , mInputRow(0)
99 : , mOutputRow(0)
100 0 : , mHasAlpha(true)
101 : {
102 0 : MOZ_ASSERT(gfxPrefs::ImageDownscaleDuringDecodeEnabled(),
103 : "Downscaling even though downscale-during-decode is disabled?");
104 0 : }
105 :
106 0 : ~DownscalingFilter()
107 : {
108 0 : ReleaseWindow();
109 0 : }
110 :
111 : template <typename... Rest>
112 0 : nsresult Configure(const DownscalingConfig& aConfig, Rest... aRest)
113 : {
114 0 : nsresult rv = mNext.Configure(aRest...);
115 0 : if (NS_FAILED(rv)) {
116 0 : return rv;
117 : }
118 :
119 0 : if (mNext.IsValidPalettedPipe()) {
120 0 : NS_WARNING("Created a downscaler for a paletted surface?");
121 0 : return NS_ERROR_INVALID_ARG;
122 : }
123 0 : if (mNext.InputSize() == aConfig.mInputSize) {
124 0 : NS_WARNING("Created a downscaler, but not downscaling?");
125 0 : return NS_ERROR_INVALID_ARG;
126 : }
127 0 : if (mNext.InputSize().width > aConfig.mInputSize.width) {
128 0 : NS_WARNING("Created a downscaler, but width is larger");
129 0 : return NS_ERROR_INVALID_ARG;
130 : }
131 0 : if (mNext.InputSize().height > aConfig.mInputSize.height) {
132 0 : NS_WARNING("Created a downscaler, but height is larger");
133 0 : return NS_ERROR_INVALID_ARG;
134 : }
135 0 : if (aConfig.mInputSize.width <= 0 || aConfig.mInputSize.height <= 0) {
136 0 : NS_WARNING("Invalid input size for DownscalingFilter");
137 0 : return NS_ERROR_INVALID_ARG;
138 : }
139 :
140 0 : mInputSize = aConfig.mInputSize;
141 0 : gfx::IntSize outputSize = mNext.InputSize();
142 0 : mScale = gfxSize(double(mInputSize.width) / outputSize.width,
143 0 : double(mInputSize.height) / outputSize.height);
144 0 : mHasAlpha = aConfig.mFormat == gfx::SurfaceFormat::B8G8R8A8;
145 :
146 0 : ReleaseWindow();
147 :
148 0 : auto resizeMethod = gfx::ConvolutionFilter::ResizeMethod::LANCZOS3;
149 0 : if (!mXFilter.ComputeResizeFilter(resizeMethod, mInputSize.width, outputSize.width) ||
150 0 : !mYFilter.ComputeResizeFilter(resizeMethod, mInputSize.height, outputSize.height)) {
151 0 : NS_WARNING("Failed to compute filters for image downscaling");
152 0 : return NS_ERROR_OUT_OF_MEMORY;
153 : }
154 :
155 : // Allocate the buffer, which contains scanlines of the input image.
156 0 : mRowBuffer.reset(new (fallible)
157 0 : uint8_t[PaddedWidthInBytes(mInputSize.width)]);
158 0 : if (MOZ_UNLIKELY(!mRowBuffer)) {
159 0 : return NS_ERROR_OUT_OF_MEMORY;
160 : }
161 :
162 : // Clear the buffer to avoid writing uninitialized memory to the output.
163 0 : memset(mRowBuffer.get(), 0, PaddedWidthInBytes(mInputSize.width));
164 :
165 : // Allocate the window, which contains horizontally downscaled scanlines. (We
166 : // can store scanlines which are already downscaled because our downscaling
167 : // filter is separable.)
168 0 : mWindowCapacity = mYFilter.MaxFilter();
169 0 : mWindow.reset(new (fallible) uint8_t*[mWindowCapacity]);
170 0 : if (MOZ_UNLIKELY(!mWindow)) {
171 0 : return NS_ERROR_OUT_OF_MEMORY;
172 : }
173 :
174 : // Allocate the "window" of recent rows that we keep in memory as input for
175 : // the downscaling code. We intentionally iterate through the entire array
176 : // even if an allocation fails, to ensure that all the pointers in it are
177 : // either valid or nullptr. That in turn ensures that ReleaseWindow() can
178 : // clean up correctly.
179 0 : bool anyAllocationFailed = false;
180 0 : const size_t windowRowSizeInBytes = PaddedWidthInBytes(outputSize.width);
181 0 : for (int32_t i = 0; i < mWindowCapacity; ++i) {
182 0 : mWindow[i] = new (fallible) uint8_t[windowRowSizeInBytes];
183 0 : anyAllocationFailed = anyAllocationFailed || mWindow[i] == nullptr;
184 : }
185 :
186 0 : if (MOZ_UNLIKELY(anyAllocationFailed)) {
187 0 : return NS_ERROR_OUT_OF_MEMORY;
188 : }
189 :
190 0 : ConfigureFilter(mInputSize, sizeof(uint32_t));
191 0 : return NS_OK;
192 : }
193 :
194 0 : Maybe<SurfaceInvalidRect> TakeInvalidRect() override
195 : {
196 0 : Maybe<SurfaceInvalidRect> invalidRect = mNext.TakeInvalidRect();
197 :
198 0 : if (invalidRect) {
199 : // Compute the input space invalid rect by scaling.
200 0 : invalidRect->mInputSpaceRect.ScaleRoundOut(mScale.width, mScale.height);
201 : }
202 :
203 0 : return invalidRect;
204 : }
205 :
206 : protected:
207 0 : uint8_t* DoResetToFirstRow() override
208 : {
209 0 : mNext.ResetToFirstRow();
210 :
211 0 : mInputRow = 0;
212 0 : mOutputRow = 0;
213 0 : mRowsInWindow = 0;
214 :
215 0 : return GetRowPointer();
216 : }
217 :
218 0 : uint8_t* DoAdvanceRow() override
219 : {
220 0 : if (mInputRow >= mInputSize.height) {
221 0 : NS_WARNING("Advancing DownscalingFilter past the end of the input");
222 0 : return nullptr;
223 : }
224 :
225 0 : if (mOutputRow >= mNext.InputSize().height) {
226 0 : NS_WARNING("Advancing DownscalingFilter past the end of the output");
227 0 : return nullptr;
228 : }
229 :
230 0 : int32_t filterOffset = 0;
231 0 : int32_t filterLength = 0;
232 0 : mYFilter.GetFilterOffsetAndLength(mOutputRow,
233 : &filterOffset, &filterLength);
234 :
235 0 : int32_t inputRowToRead = filterOffset + mRowsInWindow;
236 0 : MOZ_ASSERT(mInputRow <= inputRowToRead, "Reading past end of input");
237 0 : if (mInputRow == inputRowToRead) {
238 0 : mXFilter.ConvolveHorizontally(mRowBuffer.get(), mWindow[mRowsInWindow++], mHasAlpha);
239 : }
240 :
241 0 : MOZ_ASSERT(mOutputRow < mNext.InputSize().height,
242 : "Writing past end of output");
243 :
244 0 : while (mRowsInWindow == filterLength) {
245 0 : DownscaleInputRow();
246 :
247 0 : if (mOutputRow == mNext.InputSize().height) {
248 0 : break; // We're done.
249 : }
250 :
251 0 : mYFilter.GetFilterOffsetAndLength(mOutputRow,
252 : &filterOffset, &filterLength);
253 : }
254 :
255 0 : mInputRow++;
256 :
257 0 : return mInputRow < mInputSize.height ? GetRowPointer()
258 0 : : nullptr;
259 : }
260 :
261 : private:
262 0 : uint8_t* GetRowPointer() const { return mRowBuffer.get(); }
263 :
264 0 : static size_t PaddedWidthInBytes(size_t aLogicalWidth)
265 : {
266 : // Convert from width in BGRA/BGRX pixels to width in bytes, padding
267 : // to handle overreads by the SIMD code inside Skia.
268 0 : return gfx::ConvolutionFilter::PadBytesForSIMD(aLogicalWidth * sizeof(uint32_t));
269 : }
270 :
271 0 : void DownscaleInputRow()
272 : {
273 0 : MOZ_ASSERT(mOutputRow < mNext.InputSize().height,
274 : "Writing past end of output");
275 :
276 0 : int32_t filterOffset = 0;
277 0 : int32_t filterLength = 0;
278 0 : mYFilter.GetFilterOffsetAndLength(mOutputRow,
279 : &filterOffset, &filterLength);
280 :
281 0 : mNext.template WriteUnsafeComputedRow<uint32_t>([&](uint32_t* aRow,
282 0 : uint32_t aLength) {
283 0 : mYFilter.ConvolveVertically(mWindow.get(), reinterpret_cast<uint8_t*>(aRow),
284 0 : mOutputRow, mXFilter.NumValues(), mHasAlpha);
285 0 : });
286 :
287 0 : mOutputRow++;
288 :
289 0 : if (mOutputRow == mNext.InputSize().height) {
290 0 : return; // We're done.
291 : }
292 :
293 0 : int32_t newFilterOffset = 0;
294 0 : int32_t newFilterLength = 0;
295 0 : mYFilter.GetFilterOffsetAndLength(mOutputRow,
296 : &newFilterOffset, &newFilterLength);
297 :
298 0 : int diff = newFilterOffset - filterOffset;
299 0 : MOZ_ASSERT(diff >= 0, "Moving backwards in the filter?");
300 :
301 : // Shift the buffer. We're just moving pointers here, so this is cheap.
302 0 : mRowsInWindow -= diff;
303 0 : mRowsInWindow = std::max(mRowsInWindow, 0);
304 0 : for (int32_t i = 0; i < mRowsInWindow; ++i) {
305 0 : std::swap(mWindow[i], mWindow[filterLength - mRowsInWindow + i]);
306 : }
307 : }
308 :
309 0 : void ReleaseWindow()
310 : {
311 0 : if (!mWindow) {
312 0 : return;
313 : }
314 :
315 0 : for (int32_t i = 0; i < mWindowCapacity; ++i) {
316 0 : delete[] mWindow[i];
317 : }
318 :
319 0 : mWindow = nullptr;
320 0 : mWindowCapacity = 0;
321 : }
322 :
323 : Next mNext; /// The next SurfaceFilter in the chain.
324 :
325 : gfx::IntSize mInputSize; /// The size of the input image.
326 : gfxSize mScale; /// The scale factors in each dimension.
327 : /// Computed from @mInputSize and
328 : /// the next filter's input size.
329 :
330 : UniquePtr<uint8_t[]> mRowBuffer; /// The buffer into which input is written.
331 : UniquePtr<uint8_t*[]> mWindow; /// The last few rows which were written.
332 :
333 : gfx::ConvolutionFilter mXFilter; /// The Lanczos filter in X.
334 : gfx::ConvolutionFilter mYFilter; /// The Lanczos filter in Y.
335 :
336 : int32_t mWindowCapacity; /// How many rows the window contains.
337 :
338 : int32_t mRowsInWindow; /// How many rows we've buffered in the window.
339 : int32_t mInputRow; /// The current row we're reading. (0-indexed)
340 : int32_t mOutputRow; /// The current row we're writing. (0-indexed)
341 :
342 : bool mHasAlpha; /// If true, the image has transparency.
343 : };
344 :
345 : #endif
346 :
347 : } // namespace image
348 : } // namespace mozilla
349 :
350 : #endif // mozilla_image_DownscalingFilter_h
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