1/*
2 * Copyright (C) 2006 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "GIFImageDecoder.h"
28
29#include "GIFImageReader.h"
30#include <limits>
31
32namespace WebCore {
33
34GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption, GammaAndColorProfileOption gammaAndColorProfileOption)
35 : ScalableImageDecoder(alphaOption, gammaAndColorProfileOption)
36{
37}
38
39GIFImageDecoder::~GIFImageDecoder() = default;
40
41void GIFImageDecoder::setData(SharedBuffer& data, bool allDataReceived)
42{
43 if (failed())
44 return;
45
46 ScalableImageDecoder::setData(data, allDataReceived);
47 if (m_reader)
48 m_reader->setData(&data);
49}
50
51bool GIFImageDecoder::setSize(const IntSize& size)
52{
53 if (ScalableImageDecoder::encodedDataStatus() >= EncodedDataStatus::SizeAvailable && this->size() == size)
54 return true;
55
56 if (!ScalableImageDecoder::setSize(size))
57 return false;
58
59 prepareScaleDataIfNecessary();
60 return true;
61}
62
63size_t GIFImageDecoder::frameCount() const
64{
65 const_cast<GIFImageDecoder*>(this)->decode(std::numeric_limits<unsigned>::max(), GIFFrameCountQuery, isAllDataReceived());
66 return m_frameBufferCache.size();
67}
68
69RepetitionCount GIFImageDecoder::repetitionCount() const
70{
71 // This value can arrive at any point in the image data stream. Most GIFs
72 // in the wild declare it near the beginning of the file, so it usually is
73 // set by the time we've decoded the size, but (depending on the GIF and the
74 // packets sent back by the webserver) not always. If the reader hasn't
75 // seen a loop count yet, it will return cLoopCountNotSeen, in which case we
76 // should default to looping once (the initial value for
77 // |m_repetitionCount|).
78 //
79 // There are some additional wrinkles here. First, ImageSource::clear()
80 // may destroy the reader, making the result from the reader _less_
81 // authoritative on future calls if the recreated reader hasn't seen the
82 // loop count. We don't need to special-case this because in this case the
83 // new reader will once again return cLoopCountNotSeen, and we won't
84 // overwrite the cached correct value.
85 //
86 // Second, a GIF might never set a loop count at all, in which case we
87 // should continue to treat it as a "loop once" animation. We don't need
88 // special code here either, because in this case we'll never change
89 // |m_repetitionCount| from its default value.
90 //
91 // Third, we use the same GIFImageReader for counting frames and we might
92 // see the loop count and then encounter a decoding error which happens
93 // later in the stream. It is also possible that no frames are in the
94 // stream. In these cases we should just loop once.
95 if (failed() || (m_reader && (!m_reader->imagesCount())))
96 m_repetitionCount = RepetitionCountOnce;
97 else if (m_reader && m_reader->loopCount() != cLoopCountNotSeen)
98 m_repetitionCount = m_reader->loopCount() > 0 ? m_reader->loopCount() + 1 : m_reader->loopCount();
99 return m_repetitionCount;
100}
101
102size_t GIFImageDecoder::findFirstRequiredFrameToDecode(size_t frameIndex)
103{
104 // The first frame doesn't depend on any other.
105 if (!frameIndex)
106 return 0;
107
108 for (size_t i = frameIndex; i > 0; --i) {
109 auto& frame = m_frameBufferCache[i - 1];
110
111 // Frames with disposal method RestoreToPrevious are useless, skip them.
112 if (frame.disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious)
113 continue;
114
115 // At this point the disposal method can be Unspecified, DoNotDispose or RestoreToBackground.
116 // In every case, if the frame is complete we can start decoding the next one.
117 if (frame.isComplete())
118 return i;
119
120 // If the disposal method of this frame is RestoreToBackground and it fills the whole area,
121 // the next frame's backing store is initialized to transparent, so we start decoding with it.
122 if (frame.disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToBackground) {
123 // We cannot use frame.backingStore()->frameRect() here, because it has been cleared
124 // when the frame was removed from the cache. We need to get the values from the
125 // reader context.
126 const auto* frameContext = m_reader->frameContext(i - 1);
127 ASSERT(frameContext);
128 IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
129 // We would need to scale frameRect and check whether it fills the whole scaledSize(). But
130 // can check whether the original frameRect fills size() instead. If the frame fills the
131 // whole area then it can be decoded without dependencies.
132 if (frameRect.contains({ { }, size() }))
133 return i;
134 }
135 }
136
137 return 0;
138}
139
140ScalableImageDecoderFrame* GIFImageDecoder::frameBufferAtIndex(size_t index)
141{
142 if (index >= frameCount())
143 return 0;
144
145 auto& frame = m_frameBufferCache[index];
146 if (!frame.isComplete()) {
147 for (auto i = findFirstRequiredFrameToDecode(index); i <= index; i++)
148 decode(i + 1, GIFFullQuery, isAllDataReceived());
149 }
150
151 return &frame;
152}
153
154bool GIFImageDecoder::setFailed()
155{
156 m_reader = nullptr;
157 return ScalableImageDecoder::setFailed();
158}
159
160void GIFImageDecoder::clearFrameBufferCache(size_t clearBeforeFrame)
161{
162 // In some cases, like if the decoder was destroyed while animating, we
163 // can be asked to clear more frames than we currently have.
164 if (m_frameBufferCache.isEmpty())
165 return; // Nothing to do.
166
167 // The "-1" here is tricky. It does not mean that |clearBeforeFrame| is the
168 // last frame we wish to preserve, but rather that we never want to clear
169 // the very last frame in the cache: it's empty (so clearing it is
170 // pointless), it's partial (so we don't want to clear it anyway), or the
171 // cache could be enlarged with a future setData() call and it could be
172 // needed to construct the next frame (see comments below). Callers can
173 // always use ImageSource::clear(true, ...) to completely free the memory in
174 // this case.
175 clearBeforeFrame = std::min(clearBeforeFrame, m_frameBufferCache.size() - 1);
176 const Vector<ScalableImageDecoderFrame>::iterator end(m_frameBufferCache.begin() + clearBeforeFrame);
177
178 // We need to preserve frames such that:
179 // * We don't clear |end|
180 // * We don't clear the frame we're currently decoding
181 // * We don't clear any frame from which a future initFrameBuffer() call
182 // will copy bitmap data
183 // All other frames can be cleared. Because of the constraints on when
184 // ImageSource::clear() can be called (see ImageSource.h), we're guaranteed
185 // not to have non-empty frames after the frame we're currently decoding.
186 // So, scan backwards from |end| as follows:
187 // * If the frame is empty, we're still past any frames we care about.
188 // * If the frame is complete, but is DisposalMethod::RestoreToPrevious, we'll
189 // skip over it in future initFrameBuffer() calls. We can clear it
190 // unless it's |end|, and keep scanning. For any other disposal method,
191 // stop scanning, as we've found the frame initFrameBuffer() will need
192 // next.
193 // * If the frame is partial, we're decoding it, so don't clear it; if it
194 // has a disposal method other than DisposalMethod::RestoreToPrevious, stop
195 // scanning, as we'll only need this frame when decoding the next one.
196 Vector<ScalableImageDecoderFrame>::iterator i(end);
197 for (; (i != m_frameBufferCache.begin()) && (i->isInvalid() || (i->disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious)); --i) {
198 if (i->isComplete() && (i != end))
199 i->clear();
200 }
201
202 // Now |i| holds the last frame we need to preserve; clear prior frames.
203 for (Vector<ScalableImageDecoderFrame>::iterator j(m_frameBufferCache.begin()); j != i; ++j) {
204 ASSERT(!j->isPartial());
205 if (!j->isInvalid())
206 j->clear();
207 }
208}
209
210bool GIFImageDecoder::haveDecodedRow(unsigned frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
211{
212 const GIFFrameContext* frameContext = m_reader->frameContext();
213 // The pixel data and coordinates supplied to us are relative to the frame's
214 // origin within the entire image size, i.e.
215 // (frameContext->xOffset, frameContext->yOffset). There is no guarantee
216 // that width == (size().width() - frameContext->xOffset), so
217 // we must ensure we don't run off the end of either the source data or the
218 // row's X-coordinates.
219 int xBegin = upperBoundScaledX(frameContext->xOffset);
220 int yBegin = upperBoundScaledY(frameContext->yOffset + rowNumber);
221 int xEnd = lowerBoundScaledX(std::min(static_cast<int>(frameContext->xOffset + width), size().width()) - 1, xBegin + 1) + 1;
222 int yEnd = lowerBoundScaledY(std::min(static_cast<int>(frameContext->yOffset + rowNumber + repeatCount), size().height()) - 1, yBegin + 1) + 1;
223 if (rowBuffer.isEmpty() || (xBegin < 0) || (yBegin < 0) || (xEnd <= xBegin) || (yEnd <= yBegin))
224 return true;
225
226 // Get the colormap.
227 const unsigned char* colorMap;
228 unsigned colorMapSize;
229 if (frameContext->isLocalColormapDefined) {
230 colorMap = m_reader->localColormap(frameContext);
231 colorMapSize = m_reader->localColormapSize(frameContext);
232 } else {
233 colorMap = m_reader->globalColormap();
234 colorMapSize = m_reader->globalColormapSize();
235 }
236 if (!colorMap)
237 return true;
238
239 // Initialize the frame if necessary.
240 auto& buffer = m_frameBufferCache[frameIndex];
241 if ((buffer.isInvalid() && !initFrameBuffer(frameIndex)) || !buffer.hasBackingStore())
242 return false;
243
244 auto* currentAddress = buffer.backingStore()->pixelAt(xBegin, yBegin);
245 // Write one row's worth of data into the frame.
246 for (int x = xBegin; x < xEnd; ++x) {
247 const unsigned char sourceValue = rowBuffer[(m_scaled ? m_scaledColumns[x] : x) - frameContext->xOffset];
248 if ((!frameContext->isTransparent || (sourceValue != frameContext->tpixel)) && (sourceValue < colorMapSize)) {
249 const size_t colorIndex = static_cast<size_t>(sourceValue) * 3;
250 buffer.backingStore()->setPixel(currentAddress, colorMap[colorIndex], colorMap[colorIndex + 1], colorMap[colorIndex + 2], 255);
251 } else {
252 m_currentBufferSawAlpha = true;
253 // We may or may not need to write transparent pixels to the buffer.
254 // If we're compositing against a previous image, it's wrong, and if
255 // we're writing atop a cleared, fully transparent buffer, it's
256 // unnecessary; but if we're decoding an interlaced gif and
257 // displaying it "Haeberli"-style, we must write these for passes
258 // beyond the first, or the initial passes will "show through" the
259 // later ones.
260 if (writeTransparentPixels)
261 buffer.backingStore()->setPixel(currentAddress, 0, 0, 0, 0);
262 }
263 ++currentAddress;
264 }
265
266 // Tell the frame to copy the row data if need be.
267 if (repeatCount > 1)
268 buffer.backingStore()->repeatFirstRow(IntRect(xBegin, yBegin, xEnd - xBegin , yEnd - yBegin));
269
270 return true;
271}
272
273bool GIFImageDecoder::frameComplete(unsigned frameIndex, unsigned frameDuration, ScalableImageDecoderFrame::DisposalMethod disposalMethod)
274{
275 // Initialize the frame if necessary. Some GIFs insert do-nothing frames,
276 // in which case we never reach haveDecodedRow() before getting here.
277 auto& buffer = m_frameBufferCache[frameIndex];
278 if (buffer.isInvalid() && !initFrameBuffer(frameIndex))
279 return false; // initFrameBuffer() has already called setFailed().
280
281 buffer.setDecodingStatus(DecodingStatus::Complete);
282 buffer.setDuration(Seconds::fromMilliseconds(frameDuration));
283 buffer.setDisposalMethod(disposalMethod);
284
285 if (!m_currentBufferSawAlpha) {
286 IntRect rect = buffer.backingStore()->frameRect();
287
288 // The whole frame was non-transparent, so it's possible that the entire
289 // resulting buffer was non-transparent, and we can setHasAlpha(false).
290 if (rect.contains(IntRect(IntPoint(), scaledSize())))
291 buffer.setHasAlpha(false);
292 else if (frameIndex) {
293 // Tricky case. This frame does not have alpha only if everywhere
294 // outside its rect doesn't have alpha. To know whether this is
295 // true, we check the start state of the frame -- if it doesn't have
296 // alpha, we're safe.
297 //
298 // First skip over prior DisposalMethod::RestoreToPrevious frames (since they
299 // don't affect the start state of this frame) the same way we do in
300 // initFrameBuffer().
301 const auto* prevBuffer = &m_frameBufferCache[--frameIndex];
302 while (frameIndex && (prevBuffer->disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious))
303 prevBuffer = &m_frameBufferCache[--frameIndex];
304
305 // Now, if we're at a DisposalMethod::Unspecified or DisposalMethod::DoNotDispose frame, then
306 // we can say we have no alpha if that frame had no alpha. But
307 // since in initFrameBuffer() we already copied that frame's alpha
308 // state into the current frame's, we need do nothing at all here.
309 //
310 // The only remaining case is a DisposalMethod::RestoreToBackground frame. If
311 // it had no alpha, and its rect is contained in the current frame's
312 // rect, we know the current frame has no alpha.
313 IntRect prevRect = prevBuffer->backingStore()->frameRect();
314 if ((prevBuffer->disposalMethod() == ScalableImageDecoderFrame::DisposalMethod::RestoreToBackground) && !prevBuffer->hasAlpha() && rect.contains(prevRect))
315 buffer.setHasAlpha(false);
316 }
317 }
318
319 return true;
320}
321
322void GIFImageDecoder::gifComplete()
323{
324 // Cache the repetition count, which is now as authoritative as it's ever
325 // going to be.
326 repetitionCount();
327
328 m_reader = nullptr;
329}
330
331void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query, bool allDataReceived)
332{
333 if (failed())
334 return;
335
336 if (!m_reader) {
337 m_reader = std::make_unique<GIFImageReader>(this);
338 m_reader->setData(m_data.get());
339 }
340
341 if (query == GIFSizeQuery) {
342 if (!m_reader->decode(GIFSizeQuery, haltAtFrame))
343 setFailed();
344 return;
345 }
346
347 if (!m_reader->decode(GIFFrameCountQuery, haltAtFrame)) {
348 setFailed();
349 return;
350 }
351
352 m_frameBufferCache.resize(m_reader->imagesCount());
353
354 if (query == GIFFrameCountQuery)
355 return;
356
357 if (!m_reader->decode(GIFFullQuery, haltAtFrame)) {
358 setFailed();
359 return;
360 }
361
362 // It is also a fatal error if all data is received but we failed to decode
363 // all frames completely.
364 if (allDataReceived && haltAtFrame >= m_frameBufferCache.size() && m_reader)
365 setFailed();
366}
367
368bool GIFImageDecoder::initFrameBuffer(unsigned frameIndex)
369{
370 // Initialize the frame rect in our buffer.
371 const GIFFrameContext* frameContext = m_reader->frameContext();
372 IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
373 auto* const buffer = &m_frameBufferCache[frameIndex];
374
375 if (!frameIndex) {
376 // This is the first frame, so we're not relying on any previous data.
377 if (!buffer->initialize(scaledSize(), m_premultiplyAlpha))
378 return setFailed();
379 } else {
380 // The starting state for this frame depends on the previous frame's
381 // disposal method.
382 //
383 // Frames that use the DisposalMethod::RestoreToPrevious method are effectively
384 // no-ops in terms of changing the starting state of a frame compared to
385 // the starting state of the previous frame, so skip over them. (If the
386 // first frame specifies this method, it will get treated like
387 // DisposalMethod::RestoreToBackground below and reset to a completely empty image.)
388 const auto* prevBuffer = &m_frameBufferCache[--frameIndex];
389 auto prevMethod = prevBuffer->disposalMethod();
390 while (frameIndex && (prevMethod == ScalableImageDecoderFrame::DisposalMethod::RestoreToPrevious)) {
391 prevBuffer = &m_frameBufferCache[--frameIndex];
392 prevMethod = prevBuffer->disposalMethod();
393 }
394
395 ASSERT(prevBuffer->isComplete());
396
397 if ((prevMethod == ScalableImageDecoderFrame::DisposalMethod::Unspecified) || (prevMethod == ScalableImageDecoderFrame::DisposalMethod::DoNotDispose)) {
398 // Preserve the last frame as the starting state for this frame.
399 if (!prevBuffer->backingStore() || !buffer->initialize(*prevBuffer->backingStore()))
400 return setFailed();
401 } else {
402 // We want to clear the previous frame to transparent, without
403 // affecting pixels in the image outside of the frame.
404 IntRect prevRect = prevBuffer->backingStore()->frameRect();
405 const IntSize& bufferSize = scaledSize();
406 if (!frameIndex || prevRect.contains(IntRect(IntPoint(), scaledSize()))) {
407 // Clearing the first frame, or a frame the size of the whole
408 // image, results in a completely empty image.
409 if (!buffer->initialize(bufferSize, m_premultiplyAlpha))
410 return setFailed();
411 } else {
412 // Copy the whole previous buffer, then clear just its frame.
413 if (!prevBuffer->backingStore() || !buffer->initialize(*prevBuffer->backingStore()))
414 return setFailed();
415 buffer->backingStore()->clearRect(prevRect);
416 buffer->setHasAlpha(true);
417 }
418 }
419 }
420
421 // Make sure the frameRect doesn't extend outside the buffer.
422 if (frameRect.maxX() > size().width())
423 frameRect.setWidth(size().width() - frameContext->xOffset);
424 if (frameRect.maxY() > size().height())
425 frameRect.setHeight(size().height() - frameContext->yOffset);
426
427 int left = upperBoundScaledX(frameRect.x());
428 int right = lowerBoundScaledX(frameRect.maxX(), left);
429 int top = upperBoundScaledY(frameRect.y());
430 int bottom = lowerBoundScaledY(frameRect.maxY(), top);
431 buffer->backingStore()->setFrameRect(IntRect(left, top, right - left, bottom - top));
432
433 // Update our status to be partially complete.
434 buffer->setDecodingStatus(DecodingStatus::Partial);
435
436 // Reset the alpha pixel tracker for this frame.
437 m_currentBufferSawAlpha = false;
438 return true;
439}
440
441} // namespace WebCore
442