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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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