1/*
2 * Copyright (C) 2004, 2005, 2006, 2008 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 "ImageSource.h"
28
29#if USE(CG)
30#include "ImageSourceCG.h"
31
32#include "ImageOrientation.h"
33#include "IntPoint.h"
34#include "IntSize.h"
35#include "MIMETypeRegistry.h"
36#include "SharedBuffer.h"
37#if !PLATFORM(IOS)
38#include <ApplicationServices/ApplicationServices.h>
39#else
40#include <CoreGraphics/CGImagePrivate.h>
41#include <CoreGraphics/CoreGraphics.h>
42#include <ImageIO/CGImageSourcePrivate.h>
43#include <ImageIO/ImageIO.h>
44#include <wtf/RetainPtr.h>
45#endif
46
47namespace WebCore {
48
49const CFStringRef WebCoreCGImagePropertyAPNGUnclampedDelayTime = CFSTR("UnclampedDelayTime");
50const CFStringRef WebCoreCGImagePropertyAPNGDelayTime = CFSTR("DelayTime");
51const CFStringRef WebCoreCGImagePropertyAPNGLoopCount = CFSTR("LoopCount");
52
53const CFStringRef kCGImageSourceShouldPreferRGB32 = CFSTR("kCGImageSourceShouldPreferRGB32");
54const CFStringRef kCGImageSourceSkipMetadata = CFSTR("kCGImageSourceSkipMetadata");
55
56#if !PLATFORM(COCOA)
57size_t sharedBufferGetBytesAtPosition(void* info, void* buffer, off_t position, size_t count)
58{
59    SharedBuffer* sharedBuffer = static_cast<SharedBuffer*>(info);
60    size_t sourceSize = sharedBuffer->size();
61    if (position >= sourceSize)
62        return 0;
63
64    const char* source = sharedBuffer->data() + position;
65    size_t amount = std::min<size_t>(count, sourceSize - position);
66    memcpy(buffer, source, amount);
67    return amount;
68}
69
70void sharedBufferRelease(void* info)
71{
72    SharedBuffer* sharedBuffer = static_cast<SharedBuffer*>(info);
73    sharedBuffer->deref();
74}
75#endif
76
77ImageSource::ImageSource(ImageSource::AlphaOption, ImageSource::GammaAndColorProfileOption)
78    : m_decoder(0)
79#if PLATFORM(IOS)
80    , m_baseSubsampling(0)
81    , m_isProgressive(false)
82#endif
83{
84    // FIXME: AlphaOption and GammaAndColorProfileOption are ignored.
85}
86
87ImageSource::~ImageSource()
88{
89    clear(true);
90}
91
92void ImageSource::clear(bool destroyAllFrames, size_t, SharedBuffer* data, bool allDataReceived)
93{
94    // Recent versions of ImageIO discard previously decoded image frames if the client
95    // application no longer holds references to them, so there's no need to throw away
96    // the decoder unless we're explicitly asked to destroy all of the frames.
97    if (!destroyAllFrames)
98        return;
99
100    if (m_decoder) {
101        CFRelease(m_decoder);
102        m_decoder = 0;
103    }
104    if (data)
105        setData(data, allDataReceived);
106}
107
108#if !PLATFORM(IOS)
109static CFDictionaryRef imageSourceOptions(ImageSource::ShouldSkipMetadata skipMetaData)
110{
111    static CFDictionaryRef options;
112
113    if (!options) {
114        const unsigned numOptions = 3;
115        const CFBooleanRef imageSourceSkipMetadata = (skipMetaData == ImageSource::SkipMetadata) ? kCFBooleanTrue : kCFBooleanFalse;
116        const void* keys[numOptions] = { kCGImageSourceShouldCache, kCGImageSourceShouldPreferRGB32, kCGImageSourceSkipMetadata };
117        const void* values[numOptions] = { kCFBooleanTrue, kCFBooleanTrue, imageSourceSkipMetadata };
118        options = CFDictionaryCreate(NULL, keys, values, numOptions,
119            &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
120    }
121    return options;
122}
123#else
124CFDictionaryRef ImageSource::imageSourceOptions(ShouldSkipMetadata skipMetaData, int requestedSubsampling) const
125{
126    static CFDictionaryRef options[4] = {nullptr, nullptr, nullptr, nullptr};
127    int subsampling = std::min(3, m_isProgressive || requestedSubsampling < 0 ? 0 : (requestedSubsampling + m_baseSubsampling));
128
129    if (!options[subsampling]) {
130        int subsampleInt = 1 << subsampling; // [0..3] => [1, 2, 4, 8]
131        RetainPtr<CFNumberRef> subsampleNumber = adoptCF(CFNumberCreate(nullptr,  kCFNumberIntType,  &subsampleInt));
132        const CFIndex numOptions = 4;
133        const CFBooleanRef imageSourceSkipMetaData = (skipMetaData == ImageSource::SkipMetadata) ? kCFBooleanTrue : kCFBooleanFalse;
134        const void* keys[numOptions] = { kCGImageSourceShouldCache, kCGImageSourceShouldPreferRGB32, kCGImageSourceSubsampleFactor, kCGImageSourceSkipMetadata };
135        const void* values[numOptions] = { kCFBooleanTrue, kCFBooleanTrue, subsampleNumber.get(), imageSourceSkipMetaData };
136        options[subsampling] = CFDictionaryCreate(nullptr, keys, values, numOptions, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
137    }
138    return options[subsampling];
139}
140#endif
141
142bool ImageSource::initialized() const
143{
144    return m_decoder;
145}
146
147void ImageSource::setData(SharedBuffer* data, bool allDataReceived)
148{
149#if PLATFORM(COCOA)
150    if (!m_decoder)
151        m_decoder = CGImageSourceCreateIncremental(0);
152    // On Mac the NSData inside the SharedBuffer can be secretly appended to without the SharedBuffer's knowledge.  We use SharedBuffer's ability
153    // to wrap itself inside CFData to get around this, ensuring that ImageIO is really looking at the SharedBuffer.
154    CGImageSourceUpdateData(m_decoder, data->createCFData().get(), allDataReceived);
155#else
156    if (!m_decoder) {
157        m_decoder = CGImageSourceCreateIncremental(0);
158    } else if (allDataReceived) {
159#if !PLATFORM(WIN)
160        // 10.6 bug workaround: image sources with final=false fail to draw into PDF contexts, so re-create image source
161        // when data is complete. <rdar://problem/7874035> (<http://openradar.appspot.com/7874035>)
162        CFRelease(m_decoder);
163        m_decoder = CGImageSourceCreateIncremental(0);
164#endif
165    }
166    // Create a CGDataProvider to wrap the SharedBuffer.
167    data->ref();
168    // We use the GetBytesAtPosition callback rather than the GetBytePointer one because SharedBuffer
169    // does not provide a way to lock down the byte pointer and guarantee that it won't move, which
170    // is a requirement for using the GetBytePointer callback.
171    CGDataProviderDirectCallbacks providerCallbacks = { 0, 0, 0, sharedBufferGetBytesAtPosition, sharedBufferRelease };
172    RetainPtr<CGDataProviderRef> dataProvider = adoptCF(CGDataProviderCreateDirect(data, data->size(), &providerCallbacks));
173    CGImageSourceUpdateDataProvider(m_decoder, dataProvider.get(), allDataReceived);
174#endif
175}
176
177String ImageSource::filenameExtension() const
178{
179    if (!m_decoder)
180        return String();
181    CFStringRef imageSourceType = CGImageSourceGetType(m_decoder);
182    return WebCore::preferredExtensionForImageSourceType(imageSourceType);
183}
184
185bool ImageSource::isSizeAvailable()
186{
187    bool result = false;
188    CGImageSourceStatus imageSourceStatus = CGImageSourceGetStatus(m_decoder);
189
190    // Ragnaros yells: TOO SOON! You have awakened me TOO SOON, Executus!
191    if (imageSourceStatus >= kCGImageStatusIncomplete) {
192        RetainPtr<CFDictionaryRef> image0Properties = adoptCF(CGImageSourceCopyPropertiesAtIndex(m_decoder, 0, imageSourceOptions(SkipMetadata)));
193        if (image0Properties) {
194            CFNumberRef widthNumber = (CFNumberRef)CFDictionaryGetValue(image0Properties.get(), kCGImagePropertyPixelWidth);
195            CFNumberRef heightNumber = (CFNumberRef)CFDictionaryGetValue(image0Properties.get(), kCGImagePropertyPixelHeight);
196            result = widthNumber && heightNumber;
197        }
198    }
199
200    return result;
201}
202
203static ImageOrientation orientationFromProperties(CFDictionaryRef imageProperties)
204{
205    ASSERT(imageProperties);
206    CFNumberRef orientationProperty = (CFNumberRef)CFDictionaryGetValue(imageProperties, kCGImagePropertyOrientation);
207    if (!orientationProperty)
208        return DefaultImageOrientation;
209
210    int exifValue;
211    CFNumberGetValue(orientationProperty, kCFNumberIntType, &exifValue);
212    return ImageOrientation::fromEXIFValue(exifValue);
213}
214
215IntSize ImageSource::frameSizeAtIndex(size_t index, ImageOrientationDescription description) const
216{
217    RetainPtr<CFDictionaryRef> properties = adoptCF(CGImageSourceCopyPropertiesAtIndex(m_decoder, index, imageSourceOptions(SkipMetadata)));
218
219    if (!properties)
220        return IntSize();
221
222    int w = 0, h = 0;
223    CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(properties.get(), kCGImagePropertyPixelWidth);
224    if (num)
225        CFNumberGetValue(num, kCFNumberIntType, &w);
226    num = (CFNumberRef)CFDictionaryGetValue(properties.get(), kCGImagePropertyPixelHeight);
227    if (num)
228        CFNumberGetValue(num, kCFNumberIntType, &h);
229
230#if PLATFORM(IOS)
231    if (!m_isProgressive) {
232        CFDictionaryRef jfifProperties = static_cast<CFDictionaryRef>(CFDictionaryGetValue(properties.get(), kCGImagePropertyJFIFDictionary));
233        if (jfifProperties) {
234            CFBooleanRef isProgCFBool = static_cast<CFBooleanRef>(CFDictionaryGetValue(jfifProperties, kCGImagePropertyJFIFIsProgressive));
235            if (isProgCFBool)
236                m_isProgressive = CFBooleanGetValue(isProgCFBool);
237            // Workaround for <rdar://problem/5184655> - Hang rendering very large progressive JPEG. Decoding progressive
238            // images hangs for a very long time right now. Until this is fixed, don't sub-sample progressive images. This
239            // will cause them to fail our large image check and they won't be decoded.
240            // FIXME: Remove once underlying issue is fixed (<rdar://problem/5191418>)
241        }
242    }
243
244    if ((m_baseSubsampling == 0) && !m_isProgressive) {
245        IntSize subsampledSize(w, h);
246        const int cMaximumImageSizeBeforeSubsampling = 5 * 1024 * 1024;
247        while ((m_baseSubsampling < 3) && subsampledSize.width() * subsampledSize.height() > cMaximumImageSizeBeforeSubsampling) {
248            // We know the size, but the actual image is very large and should be sub-sampled.
249            // Increase the base subsampling and ask for the size again. If the image can be subsampled, the size will be
250            // greatly reduced. 4x sub-sampling will make us support up to 320MP (5MP * 4^3) images, which should be plenty.
251            // There's no callback from ImageIO when the size is available, so we do the check when we happen
252            // to check the size and its non - zero.
253            // Note: Some clients of this class don't call isSizeAvailable() so we can't rely on that.
254            ++m_baseSubsampling;
255            subsampledSize = frameSizeAtIndex(index, description.respectImageOrientation());
256        }
257        w = subsampledSize.width();
258        h = subsampledSize.height();
259    }
260#endif
261
262    if ((description.respectImageOrientation() == RespectImageOrientation) && orientationFromProperties(properties.get()).usesWidthAsHeight())
263        return IntSize(h, w);
264
265    return IntSize(w, h);
266}
267
268ImageOrientation ImageSource::orientationAtIndex(size_t index) const
269{
270    RetainPtr<CFDictionaryRef> properties = adoptCF(CGImageSourceCopyPropertiesAtIndex(m_decoder, index, imageSourceOptions(SkipMetadata)));
271    if (!properties)
272        return DefaultImageOrientation;
273
274    return orientationFromProperties(properties.get());
275}
276
277#if PLATFORM(IOS)
278IntSize ImageSource::originalSize(RespectImageOrientationEnum shouldRespectOrientation) const
279{
280    frameSizeAtIndex(0, shouldRespectOrientation);
281    RetainPtr<CFDictionaryRef> properties = adoptCF(CGImageSourceCopyPropertiesAtIndex(m_decoder, 0, imageSourceOptions(SkipMetadata, -1)));
282
283    if (!properties)
284        return IntSize();
285
286    int width = 0;
287    int height = 0;
288    CFNumberRef number = (CFNumberRef)CFDictionaryGetValue(properties.get(), kCGImagePropertyPixelWidth);
289    if (number)
290        CFNumberGetValue(number, kCFNumberIntType, &width);
291    number = static_cast<CFNumberRef>(CFDictionaryGetValue(properties.get(), kCGImagePropertyPixelHeight));
292    if (number)
293        CFNumberGetValue(number, kCFNumberIntType, &height);
294
295    if ((shouldRespectOrientation == RespectImageOrientation) && orientationFromProperties(properties.get()).usesWidthAsHeight())
296        return IntSize(height, width);
297
298    return IntSize(width, height);
299}
300#endif
301
302IntSize ImageSource::size(ImageOrientationDescription description) const
303{
304    return frameSizeAtIndex(0, description);
305}
306
307bool ImageSource::getHotSpot(IntPoint& hotSpot) const
308{
309    RetainPtr<CFDictionaryRef> properties = adoptCF(CGImageSourceCopyPropertiesAtIndex(m_decoder, 0, imageSourceOptions(SkipMetadata)));
310    if (!properties)
311        return false;
312
313    int x = -1, y = -1;
314    CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(properties.get(), CFSTR("hotspotX"));
315    if (!num || !CFNumberGetValue(num, kCFNumberIntType, &x))
316        return false;
317
318    num = (CFNumberRef)CFDictionaryGetValue(properties.get(), CFSTR("hotspotY"));
319    if (!num || !CFNumberGetValue(num, kCFNumberIntType, &y))
320        return false;
321
322    if (x < 0 || y < 0)
323        return false;
324
325    hotSpot = IntPoint(x, y);
326    return true;
327}
328
329size_t ImageSource::bytesDecodedToDetermineProperties() const
330{
331    // Measured by tracing malloc/calloc calls on Mac OS 10.6.6, x86_64.
332    // A non-zero value ensures cached images with no decoded frames still enter
333    // the live decoded resources list when the CGImageSource decodes image
334    // properties, allowing the cache to prune the partially decoded image.
335    // This value is likely to be inaccurate on other platforms, but the overall
336    // behavior is unchanged.
337    return 13088;
338}
339
340int ImageSource::repetitionCount()
341{
342    if (!initialized())
343        return cAnimationLoopOnce;
344
345    RetainPtr<CFDictionaryRef> properties = adoptCF(CGImageSourceCopyProperties(m_decoder, imageSourceOptions(SkipMetadata)));
346    if (!properties)
347        return cAnimationLoopOnce;
348
349    CFDictionaryRef gifProperties = (CFDictionaryRef)CFDictionaryGetValue(properties.get(), kCGImagePropertyGIFDictionary);
350    if (gifProperties) {
351        CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(gifProperties, kCGImagePropertyGIFLoopCount);
352
353        // No property means loop once.
354        if (!num)
355            return cAnimationLoopOnce;
356
357        int loopCount;
358        CFNumberGetValue(num, kCFNumberIntType, &loopCount);
359
360        // A property with value 0 means loop forever.
361        return loopCount ? loopCount : cAnimationLoopInfinite;
362    }
363
364    CFDictionaryRef pngProperties = (CFDictionaryRef)CFDictionaryGetValue(properties.get(), kCGImagePropertyPNGDictionary);
365    if (pngProperties) {
366        CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(pngProperties, WebCoreCGImagePropertyAPNGLoopCount);
367        if (!num)
368            return cAnimationLoopOnce;
369
370        int loopCount;
371        CFNumberGetValue(num, kCFNumberIntType, &loopCount);
372        return loopCount ? loopCount : cAnimationLoopInfinite;
373    }
374
375    // Turns out we're not an animated image after all, so we don't animate.
376    return cAnimationNone;
377}
378
379size_t ImageSource::frameCount() const
380{
381    return m_decoder ? CGImageSourceGetCount(m_decoder) : 0;
382}
383
384CGImageRef ImageSource::createFrameAtIndex(size_t index, float* scale)
385{
386    UNUSED_PARAM(scale);
387
388    if (!initialized())
389        return 0;
390
391#if !PLATFORM(IOS)
392    UNUSED_PARAM(scale);
393    RetainPtr<CGImageRef> image = adoptCF(CGImageSourceCreateImageAtIndex(m_decoder, index, imageSourceOptions(SkipMetadata)));
394#else
395    // Subsampling can be 1, 2 or 3, which means quarter-, sixteenth- and sixty-fourth-size, respectively.
396    // A zero or negative value means no subsampling.
397    int subsampling = scale ? static_cast<int>(log2f(1.0f / std::max(0.1f, std::min(1.0f, *scale)))) : -1;
398    RetainPtr<CGImageRef> image = adoptCF(CGImageSourceCreateImageAtIndex(m_decoder, index, imageSourceOptions(SkipMetadata, subsampling)));
399
400    // <rdar://problem/7371198> - CoreGraphics changed the default caching behaviour in iOS 4.0 to kCGImageCachingTransient
401    // which caused a performance regression for us since the images had to be resampled/recreated every time we called
402    // CGContextDrawImage. We now tell CG to cache the drawn images. See also <rdar://problem/14366755> -
403    // CoreGraphics needs to un-deprecate kCGImageCachingTemporary since it's still not the default.
404#if COMPILER(CLANG)
405#pragma clang diagnostic push
406#pragma clang diagnostic ignored "-Wdeprecated-declarations"
407#endif
408    CGImageSetCachingFlags(image.get(), kCGImageCachingTemporary);
409#if COMPILER(CLANG)
410#pragma clang diagnostic pop
411#endif
412    if (scale) {
413        if (subsampling > 0)
414            *scale = static_cast<float>(CGImageGetWidth(image.get())) / size(DoNotRespectImageOrientation).width();
415        else {
416            ASSERT(static_cast<int>(CGImageGetWidth(image.get())) == size(DoNotRespectImageOrientation).width());
417            *scale = 1;
418        }
419    }
420#endif // !PLATFORM(IOS)
421    CFStringRef imageUTI = CGImageSourceGetType(m_decoder);
422    static const CFStringRef xbmUTI = CFSTR("public.xbitmap-image");
423    if (!imageUTI || !CFEqual(imageUTI, xbmUTI))
424        return image.leakRef();
425
426    // If it is an xbm image, mask out all the white areas to render them transparent.
427    const CGFloat maskingColors[6] = {255, 255,  255, 255, 255, 255};
428    RetainPtr<CGImageRef> maskedImage = adoptCF(CGImageCreateWithMaskingColors(image.get(), maskingColors));
429    if (!maskedImage)
430        return image.leakRef();
431
432    return maskedImage.leakRef();
433}
434
435bool ImageSource::frameIsCompleteAtIndex(size_t index)
436{
437    ASSERT(frameCount());
438
439    // CGImageSourceGetStatusAtIndex claims that all frames of a multi-frame image are incomplete
440    // when we've not yet received the complete data for an image that is using an incremental data
441    // source (<rdar://problem/7679174>). We work around this by special-casing all frames except the
442    // last in an image and treating them as complete if they are present and reported as being
443    // incomplete. We do this on the assumption that loading new data can only modify the existing last
444    // frame or append new frames. The last frame is only treated as being complete if the image source
445    // reports it as such. This ensures that it is truly the last frame of the image rather than just
446    // the last that we currently have data for.
447
448    CGImageSourceStatus frameStatus = CGImageSourceGetStatusAtIndex(m_decoder, index);
449    if (index < frameCount() - 1)
450        return frameStatus >= kCGImageStatusIncomplete;
451
452    return frameStatus == kCGImageStatusComplete;
453}
454
455float ImageSource::frameDurationAtIndex(size_t index)
456{
457    if (!initialized())
458        return 0;
459
460    float duration = 0;
461    RetainPtr<CFDictionaryRef> properties = adoptCF(CGImageSourceCopyPropertiesAtIndex(m_decoder, index, imageSourceOptions(SkipMetadata)));
462    if (properties) {
463        CFDictionaryRef gifProperties = (CFDictionaryRef)CFDictionaryGetValue(properties.get(), kCGImagePropertyGIFDictionary);
464        if (gifProperties) {
465            if (CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(gifProperties, kCGImagePropertyGIFUnclampedDelayTime)) {
466                // Use the unclamped frame delay if it exists.
467                CFNumberGetValue(num, kCFNumberFloatType, &duration);
468            } else if (CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(gifProperties, kCGImagePropertyGIFDelayTime)) {
469                // Fall back to the clamped frame delay if the unclamped frame delay does not exist.
470                CFNumberGetValue(num, kCFNumberFloatType, &duration);
471            }
472        }
473
474        CFDictionaryRef pngProperties = (CFDictionaryRef)CFDictionaryGetValue(properties.get(), kCGImagePropertyPNGDictionary);
475        if (pngProperties) {
476            if (CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(pngProperties, WebCoreCGImagePropertyAPNGUnclampedDelayTime))
477                CFNumberGetValue(num, kCFNumberFloatType, &duration);
478            else if (CFNumberRef num = (CFNumberRef)CFDictionaryGetValue(pngProperties, WebCoreCGImagePropertyAPNGDelayTime))
479                CFNumberGetValue(num, kCFNumberFloatType, &duration);
480        }
481    }
482
483    // Many annoying ads specify a 0 duration to make an image flash as quickly as possible.
484    // We follow Firefox's behavior and use a duration of 100 ms for any frames that specify
485    // a duration of <= 10 ms. See <rdar://problem/7689300> and <http://webkit.org/b/36082>
486    // for more information.
487    if (duration < 0.011f)
488        return 0.100f;
489    return duration;
490}
491
492bool ImageSource::frameHasAlphaAtIndex(size_t index)
493{
494    if (!m_decoder)
495        return false; // FIXME: why doesn't this return true?
496
497    if (!frameIsCompleteAtIndex(index))
498        return true;
499
500    CFStringRef imageType = CGImageSourceGetType(m_decoder);
501
502    // Return false if there is no image type or the image type is JPEG, because
503    // JPEG does not support alpha transparency.
504    if (!imageType || CFEqual(imageType, CFSTR("public.jpeg")))
505        return false;
506
507    // FIXME: Could return false for other non-transparent image formats.
508    // FIXME: Could maybe return false for a GIF Frame if we have enough info in the GIF properties dictionary
509    // to determine whether or not a transparent color was defined.
510    return true;
511}
512
513unsigned ImageSource::frameBytesAtIndex(size_t index) const
514{
515    IntSize frameSize = frameSizeAtIndex(index, ImageOrientationDescription(RespectImageOrientation));
516    return frameSize.width() * frameSize.height() * 4;
517}
518
519}
520
521#endif // USE(CG)
522