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Side by Side Diff: include/codec/SkScanlineDecoder.h

Issue 1294613002: Revert of SkScaledCodec class (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Created 5 years, 4 months ago
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1 /* 1 /*
2 * Copyright 2015 Google Inc. 2 * Copyright 2015 Google Inc.
3 * 3 *
4 * Use of this source code is governed by a BSD-style license that can be 4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file. 5 * found in the LICENSE file.
6 */ 6 */
7 7
8 #ifndef SkScanlineDecoder_DEFINED 8 #ifndef SkScanlineDecoder_DEFINED
9 #define SkScanlineDecoder_DEFINED 9 #define SkScanlineDecoder_DEFINED
10 10
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39 /** 39 /**
40 * Clean up after reading/skipping scanlines. 40 * Clean up after reading/skipping scanlines.
41 * 41 *
42 * It is possible that not all scanlines will have been read/skipped. In 42 * It is possible that not all scanlines will have been read/skipped. In
43 * fact, in the case of subset decodes, it is likely that there will be 43 * fact, in the case of subset decodes, it is likely that there will be
44 * scanlines at the bottom of the image that have been ignored. 44 * scanlines at the bottom of the image that have been ignored.
45 */ 45 */
46 virtual ~SkScanlineDecoder() {} 46 virtual ~SkScanlineDecoder() {}
47 47
48 /** 48 /**
49 * Return a size that approximately supports the desired scale factor.
50 * The codec may not be able to scale efficiently to the exact scale
51 * factor requested, so return a size that approximates that scale.
52 * The returned value is the codec's suggestion for the closest valid
53 * scale that it can natively support
54 * FIXME: share this with SkCodec
55 */
56 SkISize getScaledDimensions(float desiredScale) {
57 return this->onGetScaledDimensions(desiredScale);
58 }
59
60 /**
61 * Returns the default info, corresponding to the encoded data. 49 * Returns the default info, corresponding to the encoded data.
62 */ 50 */
63 const SkImageInfo& getInfo() { return fSrcInfo; } 51 const SkImageInfo& getInfo() { return fSrcInfo; }
64 52
65 /** 53 /**
66 * Initialize on the first scanline, with the specified options. 54 * Initialize on the first scanline, with the specified options.
67 * 55 *
68 * This must be called in order to call getScanlnies or skipScanlines. If 56 * This must be called in order to call getScanlnies or skipScanlines. If
69 * it has been called before, this will require rewinding the stream. 57 * it has been called before, this will require rewinding the stream.
70 * 58 *
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140 * of the encoded data, but then never use any colors which have alpha 128 * of the encoded data, but then never use any colors which have alpha
141 * less than 100%. This function can be called *after* decoding to 129 * less than 100%. This function can be called *after* decoding to
142 * determine if such an image truly had alpha. Calling it before decoding 130 * determine if such an image truly had alpha. Calling it before decoding
143 * is undefined. 131 * is undefined.
144 * FIXME: see skbug.com/3582. 132 * FIXME: see skbug.com/3582.
145 */ 133 */
146 bool reallyHasAlpha() const { 134 bool reallyHasAlpha() const {
147 return this->onReallyHasAlpha(); 135 return this->onReallyHasAlpha();
148 } 136 }
149 137
150 /**
151 * Format of the encoded data.
152 */
153 SkEncodedFormat getEncodedFormat() const { return this->onGetEncodedFormat() ; }
154
155 /**
156 * returns true if the image must be scaled, in the y direction, after readi ng, not during.
157 * To scale afterwards, we first decode every line and then sample the lines we want afterwards.
158 * An example is interlaced pngs, where calling getScanlines once (regardles s of the count
159 * used) needs to read the entire image, therefore it is inefficient to call
160 * getScanlines more than once. Instead, it should only ever be called with all the
161 * rows needed.
162 */
163 bool requiresPostYSampling() {
164 return this->onRequiresPostYSampling();
165 }
166
167 protected: 138 protected:
168 SkScanlineDecoder(const SkImageInfo& srcInfo) 139 SkScanlineDecoder(const SkImageInfo& srcInfo)
169 : fSrcInfo(srcInfo) 140 : fSrcInfo(srcInfo)
170 , fDstInfo() 141 , fDstInfo()
171 , fCurrScanline(0) {} 142 , fCurrScanline(0) {}
172 143
173 virtual SkISize onGetScaledDimensions(float /* desiredScale */) {
174 // By default, scaling is not supported.
175 return this->getInfo().dimensions();
176 }
177
178 virtual SkEncodedFormat onGetEncodedFormat() const = 0;
179
180 virtual bool onReallyHasAlpha() const { return false; } 144 virtual bool onReallyHasAlpha() const { return false; }
181 145
182 /**
183 * returns true if the image type is hard to sample and must be scaled after reading, not during
184 * An example is interlaced pngs, where the entire image must be read for ea ch decode
185 */
186 virtual bool onRequiresPostYSampling() { return false; }
187
188 const SkImageInfo& dstInfo() const { return fDstInfo; } 146 const SkImageInfo& dstInfo() const { return fDstInfo; }
189 147
190 private: 148 private:
191 const SkImageInfo fSrcInfo; 149 const SkImageInfo fSrcInfo;
192 SkImageInfo fDstInfo; 150 SkImageInfo fDstInfo;
193 int fCurrScanline; 151 int fCurrScanline;
194 152
195 virtual SkCodec::Result onStart(const SkImageInfo& dstInfo, 153 virtual SkCodec::Result onStart(const SkImageInfo& dstInfo,
196 const SkCodec::Options& options, 154 const SkCodec::Options& options,
197 SkPMColor ctable[], int* ctableCount) = 0; 155 SkPMColor ctable[], int* ctableCount) = 0;
198 156
199 // Naive default version just calls onGetScanlines on temp memory. 157 // Naive default version just calls onGetScanlines on temp memory.
200 virtual SkCodec::Result onSkipScanlines(int countLines) { 158 virtual SkCodec::Result onSkipScanlines(int countLines) {
201 SkAutoMalloc storage(fDstInfo.minRowBytes()); 159 SkAutoMalloc storage(fDstInfo.minRowBytes());
202 // Note that we pass 0 to rowBytes so we continue to use the same memory . 160 // Note that we pass 0 to rowBytes so we continue to use the same memory .
203 // Also note that while getScanlines checks that rowBytes is big enough, 161 // Also note that while getScanlines checks that rowBytes is big enough,
204 // onGetScanlines bypasses that check. 162 // onGetScanlines bypasses that check.
205 // Calling the virtual method also means we do not double count 163 // Calling the virtual method also means we do not double count
206 // countLines. 164 // countLines.
207 return this->onGetScanlines(storage.get(), countLines, 0); 165 return this->onGetScanlines(storage.get(), countLines, 0);
208 } 166 }
209 167
210 virtual SkCodec::Result onGetScanlines(void* dst, int countLines, 168 virtual SkCodec::Result onGetScanlines(void* dst, int countLines,
211 size_t rowBytes) = 0; 169 size_t rowBytes) = 0;
212 170
213 }; 171 };
214 #endif // SkScanlineDecoder_DEFINED 172 #endif // SkScanlineDecoder_DEFINED
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