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Side by Side Diff: src/codec/SkWebpCodec.cpp

Issue 1240143002: Add the ability to decode a subset to SkCodec. (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Update comment Created 5 years, 5 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 #include "SkWebpCodec.h" 8 #include "SkWebpCodec.h"
9 #include "SkTemplates.h" 9 #include "SkTemplates.h"
10 10
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118 default: 118 default:
119 return MODE_LAST; 119 return MODE_LAST;
120 } 120 }
121 } 121 }
122 122
123 // The WebP decoding API allows us to incrementally pass chunks of bytes as we r eceive them to the 123 // The WebP decoding API allows us to incrementally pass chunks of bytes as we r eceive them to the
124 // decoder with WebPIAppend. In order to do so, we need to read chunks from the SkStream. This size 124 // decoder with WebPIAppend. In order to do so, we need to read chunks from the SkStream. This size
125 // is arbitrary. 125 // is arbitrary.
126 static const size_t BUFFER_SIZE = 4096; 126 static const size_t BUFFER_SIZE = 4096;
127 127
128 bool SkWebpCodec::onGetValidSubset(SkIRect* desiredSubset) const {
129 if (!desiredSubset) {
130 return false;
131 }
132
133 SkIRect bounds = SkIRect::MakeSize(this->getInfo().dimensions());
134 if (!desiredSubset->intersect(bounds)) {
135 return false;
136 }
137
138 // As stated below, libwebp snaps to even left and top. Make sure top and le ft are even, so we
139 // decode this exact subset.
140 // Leave right and bottom unmodified, so we suggest a slightly larger subset than requested.
141 desiredSubset->fLeft = (desiredSubset->fLeft >> 1) << 1;
142 desiredSubset->fTop = (desiredSubset->fTop >> 1) << 1;
143 return true;
144 }
145
128 SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t rowBytes, 146 SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst, size_t rowBytes,
129 const Options&, SkPMColor*, int*) { 147 const Options& options, SkPMColor*, int *) {
130 switch (this->rewindIfNeeded()) { 148 switch (this->rewindIfNeeded()) {
131 case kCouldNotRewind_RewindState: 149 case kCouldNotRewind_RewindState:
132 return kCouldNotRewind; 150 return kCouldNotRewind;
133 case kRewound_RewindState: 151 case kRewound_RewindState:
134 // Rewound to the beginning. Since creation only does a peek, the st ream is at the 152 // Rewound to the beginning. Since creation only does a peek, the st ream is at the
135 // correct position. 153 // correct position.
136 break; 154 break;
137 case kNoRewindNecessary_RewindState: 155 case kNoRewindNecessary_RewindState:
138 // Already at the right spot for decoding. 156 // Already at the right spot for decoding.
139 break; 157 break;
140 } 158 }
141 159
142 if (!conversion_possible(dstInfo, this->getInfo())) { 160 if (!conversion_possible(dstInfo, this->getInfo())) {
143 return kInvalidConversion; 161 return kInvalidConversion;
144 } 162 }
145 163
146 WebPDecoderConfig config; 164 WebPDecoderConfig config;
147 if (0 == WebPInitDecoderConfig(&config)) { 165 if (0 == WebPInitDecoderConfig(&config)) {
148 // ABI mismatch. 166 // ABI mismatch.
149 // FIXME: New enum for this? 167 // FIXME: New enum for this?
150 return kInvalidInput; 168 return kInvalidInput;
151 } 169 }
152 170
153 // Free any memory associated with the buffer. Must be called last, so we de clare it first. 171 // Free any memory associated with the buffer. Must be called last, so we de clare it first.
154 SkAutoTCallVProc<WebPDecBuffer, WebPFreeDecBuffer> autoFree(&(config.output) ); 172 SkAutoTCallVProc<WebPDecBuffer, WebPFreeDecBuffer> autoFree(&(config.output) );
155 173
156 SkISize dimensions = dstInfo.dimensions(); 174 SkIRect bounds = SkIRect::MakeSize(this->getInfo().dimensions());
157 if (this->getInfo().dimensions() != dimensions) { 175 if (!options.fSubset.isEmpty()) {
176 // Caller is requesting a subset.
177 if (!bounds.intersect(options.fSubset)) {
msarett 2015/07/21 15:19:37 Per our discussion in person, let's explicitly dis
scroggo 2015/07/21 16:48:56 Done.
178 // The subset is out of bounds.
179 return kInvalidParameters;
180 }
181
182 // This is tricky. libwebp snaps the top and left to even values. We cou ld let libwebp
183 // do the snap, and return a subset which is a different one than reques ted. The problem
184 // with that approach is that the caller may try to stitch subsets toget her, and if we
185 // returned different subsets than requested, there would be artifacts a t the boundaries.
186 // Instead, we report that we cannot support odd values for top and left ..
187 if (!SkIsAlign2(bounds.fLeft) || !SkIsAlign2(bounds.fTop)) {
188 return kInvalidParameters;
189 }
190
191 #ifdef SK_DEBUG
192 {
193 // Make a copy, since getValidSubset can change its input.
194 SkIRect subset(bounds);
195 // That said, getValidSubset should *not* change its input, in this case; otherwise
196 // getValidSubset does not match the actual subsets we can do.
197 SkASSERT(this->getValidSubset(&subset) && subset == bounds);
198 }
199 #endif
200
201 config.options.use_cropping = 1;
202 config.options.crop_left = bounds.fLeft;
203 config.options.crop_top = bounds.fTop;
204 config.options.crop_width = bounds.width();
205 config.options.crop_height = bounds.height();
206 }
207
208 SkISize dstDimensions = dstInfo.dimensions();
209 if (bounds.size() != dstDimensions) {
158 // Caller is requesting scaling. 210 // Caller is requesting scaling.
159 config.options.use_scaling = 1; 211 config.options.use_scaling = 1;
160 config.options.scaled_width = dimensions.width(); 212 config.options.scaled_width = dstDimensions.width();
161 config.options.scaled_height = dimensions.height(); 213 config.options.scaled_height = dstDimensions.height();
162 } 214 }
163 215
164 config.output.colorspace = webp_decode_mode(dstInfo.colorType(), 216 config.output.colorspace = webp_decode_mode(dstInfo.colorType(),
165 dstInfo.alphaType() == kPremul_SkAlphaType); 217 dstInfo.alphaType() == kPremul_SkAlphaType);
166 config.output.u.RGBA.rgba = (uint8_t*) dst; 218 config.output.u.RGBA.rgba = (uint8_t*) dst;
167 config.output.u.RGBA.stride = (int) rowBytes; 219 config.output.u.RGBA.stride = (int) rowBytes;
168 config.output.u.RGBA.size = dstInfo.getSafeSize(rowBytes); 220 config.output.u.RGBA.size = dstInfo.getSafeSize(rowBytes);
169 config.output.is_external_memory = 1; 221 config.output.is_external_memory = 1;
170 222
171 SkAutoTCallVProc<WebPIDecoder, WebPIDelete> idec(WebPIDecode(NULL, 0, &confi g)); 223 SkAutoTCallVProc<WebPIDecoder, WebPIDelete> idec(WebPIDecode(NULL, 0, &confi g));
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191 // Break out of the switch statement. Continue the loop. 243 // Break out of the switch statement. Continue the loop.
192 break; 244 break;
193 default: 245 default:
194 return kInvalidInput; 246 return kInvalidInput;
195 } 247 }
196 } 248 }
197 } 249 }
198 250
199 SkWebpCodec::SkWebpCodec(const SkImageInfo& info, SkStream* stream) 251 SkWebpCodec::SkWebpCodec(const SkImageInfo& info, SkStream* stream)
200 : INHERITED(info, stream) {} 252 : INHERITED(info, stream) {}
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