YYImage

YYImage

一、源码分析

1、来到YYImage.m的+ (nullable YYImage *)imageNamed:(NSString *)name;

+ (YYImage *)imageNamed:(NSString *)name {
    if (name.length == 0) return nil;
    if ([name hasSuffix:@"/"]) return nil;
    
    NSString *res = name.stringByDeletingPathExtension;
    NSString *ext = name.pathExtension;
    NSString *path = nil;
    CGFloat scale = 1;
    
    // If no extension, guess by system supported (same as UIImage).
    NSArray *exts = ext.length > 0 ? @[ext] : @[@"", @"png", @"jpeg", @"jpg", @"gif", @"webp", @"apng"];
    NSArray *scales = [NSBundle preferredScales];
    for (int s = 0; s < scales.count; s++) {
        scale = ((NSNumber *)scales[s]).floatValue;
        NSString *scaledName = [res stringByAppendingNameScale:scale];
        for (NSString *e in exts) {
            path = [[NSBundle mainBundle] pathForResource:scaledName ofType:e];
            if (path) break;
        }
        if (path) break;
    }
    if (path.length == 0) return nil;
    
    NSData *data = [NSData dataWithContentsOfFile:path];
    if (data.length == 0) return nil;
    
    return [[self alloc] initWithData:data scale:scale];
}

2、点击initWithData: scale:

• 2.1、YYImageDecoder *decoder = [YYImageDecoder decoderWithData:data scale:scale];创建了 ImageSource！！！ ，_YYImageDecoderFrame
• 2.2、YYImageFrame *frame = [decoder frameAtIndex:0 decodeForDisplay:YES];解码的操作

- (instancetype)initWithData:(NSData *)data scale:(CGFloat)scale {
    if (data.length == 0) return nil;
    if (scale <= 0) scale = [UIScreen mainScreen].scale;
    _preloadedLock = dispatch_semaphore_create(1);
    @autoreleasepool {
        // 元数据信息
        // 创建了 ImageSource！！！ ，_YYImageDecoderFrame
        YYImageDecoder *decoder = [YYImageDecoder decoderWithData:data scale:scale];
        // 解码的操作 -> imageBuffer
        YYImageFrame *frame = [decoder frameAtIndex:0 decodeForDisplay:YES];
        UIImage *image = frame.image;
        if (!image) return nil;
        self = [self initWithCGImage:image.CGImage scale:decoder.scale orientation:image.imageOrientation];
        if (!self) return nil;
        _animatedImageType = decoder.type;
        if (decoder.frameCount > 1) {
            _decoder = decoder;
            _bytesPerFrame = CGImageGetBytesPerRow(image.CGImage) * CGImageGetHeight(image.CGImage);
            _animatedImageMemorySize = _bytesPerFrame * decoder.frameCount;
        }
        self.isDecodedForDisplay = YES;
    }
    return self;
}

2.1、点击decoderWithData

+ (instancetype)decoderWithData:(NSData *)data scale:(CGFloat)scale {
    if (!data) return nil;
    YYImageDecoder *decoder = [[YYImageDecoder alloc] initWithScale:scale];
    [decoder updateData:data final:YES];
    if (decoder.frameCount == 0) return nil;
    return decoder;
}

- (BOOL)updateData:(NSData *)data final:(BOOL)final {
    BOOL result = NO;
    //递归锁！！！
    //渐进式解码（渐进式加载）
    //被同一个线程反复进入 （lockCount 同一个线程获取锁的次数）
    pthread_mutex_lock(&_lock);
    result = [self _updateData:data final:final];
    pthread_mutex_unlock(&_lock);
    return result;
}

- (BOOL)_updateData:(NSData *)data final:(BOOL)final {
    if (_finalized) return NO;
    if (data.length < _data.length) return NO;
    _finalized = final;
    _data = data;
    
    YYImageType type = YYImageDetectType((__bridge CFDataRef)data);
    if (_sourceTypeDetected) {
        if (_type != type) {
            return NO;
        } else {
            [self _updateSource];
        }
    } else {
        if (_data.length > 16) {
            _type = type;
            _sourceTypeDetected = YES;
            [self _updateSource];
        }
    }
    return YES;
}

- (void)_updateSource {
    switch (_type) {
        case YYImageTypeWebP: {
            [self _updateSourceWebP];
        } break;
            
        case YYImageTypePNG: {
            [self _updateSourceAPNG];
        } break;
            
        default: {
            [self _updateSourceImageIO];
        } break;
    }
}

- (void)_updateSourceImageIO {
    _width = 0;
    _height = 0;
    _orientation = UIImageOrientationUp;
    _loopCount = 0;
    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
    _frames = nil;
    dispatch_semaphore_signal(_framesLock);
    
    if (!_source) {
        if (_finalized) {
            _source = CGImageSourceCreateWithData((__bridge CFDataRef)_data, NULL);
        } else {
            _source = CGImageSourceCreateIncremental(NULL);
            if (_source) CGImageSourceUpdateData(_source, (__bridge CFDataRef)_data, false);
        }
    } else {
        CGImageSourceUpdateData(_source, (__bridge CFDataRef)_data, _finalized);
    }
    if (!_source) return;
    
    _frameCount = CGImageSourceGetCount(_source);
    if (_frameCount == 0) return;
    
    if (!_finalized) { // ignore multi-frame before finalized
        _frameCount = 1;
    } else {
        if (_type == YYImageTypePNG) { // use custom apng decoder and ignore multi-frame
            _frameCount = 1;
        }
        if (_type == YYImageTypeGIF) { // get gif loop count
            CFDictionaryRef properties = CGImageSourceCopyProperties(_source, NULL);
            if (properties) {
                CFDictionaryRef gif = CFDictionaryGetValue(properties, kCGImagePropertyGIFDictionary);
                if (gif) {
                    CFTypeRef loop = CFDictionaryGetValue(gif, kCGImagePropertyGIFLoopCount);
                    if (loop) CFNumberGetValue(loop, kCFNumberNSIntegerType, &_loopCount);
                }
                CFRelease(properties);
            }
        }
    }
    
    /*
     ICO, GIF, APNG may contains multi-frame.
     */
    NSMutableArray *frames = [NSMutableArray new];
    for (NSUInteger i = 0; i < _frameCount; i++) {
        _YYImageDecoderFrame *frame = [_YYImageDecoderFrame new];
        frame.index = i;
        frame.blendFromIndex = i;
        frame.hasAlpha = YES;
        frame.isFullSize = YES;
        [frames addObject:frame];
        
        CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(_source, i, NULL);
        if (properties) {
            NSTimeInterval duration = 0;
            NSInteger orientationValue = 0, width = 0, height = 0;
            CFTypeRef value = NULL;
            
            value = CFDictionaryGetValue(properties, kCGImagePropertyPixelWidth);
            if (value) CFNumberGetValue(value, kCFNumberNSIntegerType, &width);
            value = CFDictionaryGetValue(properties, kCGImagePropertyPixelHeight);
            if (value) CFNumberGetValue(value, kCFNumberNSIntegerType, &height);
            if (_type == YYImageTypeGIF) {
                CFDictionaryRef gif = CFDictionaryGetValue(properties, kCGImagePropertyGIFDictionary);
                if (gif) {
                    // Use the unclamped frame delay if it exists.
                    value = CFDictionaryGetValue(gif, kCGImagePropertyGIFUnclampedDelayTime);
                    if (!value) {
                        // Fall back to the clamped frame delay if the unclamped frame delay does not exist.
                        value = CFDictionaryGetValue(gif, kCGImagePropertyGIFDelayTime);
                    }
                    if (value) CFNumberGetValue(value, kCFNumberDoubleType, &duration);
                }
            }
            
            frame.width = width;
            frame.height = height;
            frame.duration = duration;
            
            if (i == 0 && _width + _height == 0) { // init first frame
                _width = width;
                _height = height;
                value = CFDictionaryGetValue(properties, kCGImagePropertyOrientation);
                if (value) {
                    CFNumberGetValue(value, kCFNumberNSIntegerType, &orientationValue);
                    _orientation = YYUIImageOrientationFromEXIFValue(orientationValue);
                }
            }
            CFRelease(properties);
        }
    }
    dispatch_semaphore_wait(_framesLock, DISPATCH_TIME_FOREVER);
    _frames = frames;
    dispatch_semaphore_signal(_framesLock);
}

2.2、点击frameAtIndex: decodeForDisplay:

- (YYImageFrame *)frameAtIndex:(NSUInteger)index decodeForDisplay:(BOOL)decodeForDisplay {
    YYImageFrame *result = nil;
    pthread_mutex_lock(&_lock);
    result = [self _frameAtIndex:index decodeForDisplay:decodeForDisplay];
    pthread_mutex_unlock(&_lock);
    return result;
}

- (YYImageFrame *)_frameAtIndex:(NSUInteger)index decodeForDisplay:(BOOL)decodeForDisplay {
    if (index >= _frames.count) return 0;
    _YYImageDecoderFrame *frame = [(_YYImageDecoderFrame *)_frames[index] copy];
    BOOL decoded = NO;
    BOOL extendToCanvas = NO;
    if (_type != YYImageTypeICO && decodeForDisplay) { // ICO contains multi-size frame and should not extend to canvas.
        extendToCanvas = YES;
    }
    
    if (!_needBlend) {
        CGImageRef imageRef = [self _newUnblendedImageAtIndex:index extendToCanvas:extendToCanvas decoded:&decoded];
        if (!imageRef) return nil;
        if (decodeForDisplay && !decoded) {
            CGImageRef imageRefDecoded = YYCGImageCreateDecodedCopy(imageRef, YES);
            if (imageRefDecoded) {
                CFRelease(imageRef);
                imageRef = imageRefDecoded;
                decoded = YES;
            }
        }
        UIImage *image = [UIImage imageWithCGImage:imageRef scale:_scale orientation:_orientation];
        CFRelease(imageRef);
        if (!image) return nil;
        image.isDecodedForDisplay = decoded;
        frame.image = image;
        return frame;
    }
    
    // blend
    if (![self _createBlendContextIfNeeded]) return nil;
    CGImageRef imageRef = NULL;
    
    if (_blendFrameIndex + 1 == frame.index) {
        imageRef = [self _newBlendedImageWithFrame:frame];
        _blendFrameIndex = index;
    } else { // should draw canvas from previous frame
        _blendFrameIndex = NSNotFound;
        CGContextClearRect(_blendCanvas, CGRectMake(0, 0, _width, _height));
        
        if (frame.blendFromIndex == frame.index) {
            CGImageRef unblendedImage = [self _newUnblendedImageAtIndex:index extendToCanvas:NO decoded:NULL];
            if (unblendedImage) {
                CGContextDrawImage(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), unblendedImage);
                CFRelease(unblendedImage);
            }
            imageRef = CGBitmapContextCreateImage(_blendCanvas);
            if (frame.dispose == YYImageDisposeBackground) {
                CGContextClearRect(_blendCanvas, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height));
            }
            _blendFrameIndex = index;
        } else { // canvas is not ready
            for (uint32_t i = (uint32_t)frame.blendFromIndex; i <= (uint32_t)frame.index; i++) {
                if (i == frame.index) {
                    if (!imageRef) imageRef = [self _newBlendedImageWithFrame:frame];
                } else {
                    [self _blendImageWithFrame:_frames[i]];
                }
            }
            _blendFrameIndex = index;
        }
    }
    
    if (!imageRef) return nil;
    UIImage *image = [UIImage imageWithCGImage:imageRef scale:_scale orientation:_orientation];
    CFRelease(imageRef);
    if (!image) return nil;
    
    image.isDecodedForDisplay = YES;
    frame.image = image;
    if (extendToCanvas) {
        frame.width = _width;
        frame.height = _height;
        frame.offsetX = 0;
        frame.offsetY = 0;
        frame.dispose = YYImageDisposeNone;
        frame.blend = YYImageBlendNone;
    }
    return frame;
}

- (CGImageRef)_newUnblendedImageAtIndex:(NSUInteger)index
                         extendToCanvas:(BOOL)extendToCanvas
                                decoded:(BOOL *)decoded CF_RETURNS_RETAINED {
    
    if (!_finalized && index > 0) return NULL;
    if (_frames.count <= index) return NULL;
    _YYImageDecoderFrame *frame = _frames[index];
    
    if (_source) {
        CGImageRef imageRef = CGImageSourceCreateImageAtIndex(_source, index, (CFDictionaryRef)@{(id)kCGImageSourceShouldCache:@(YES)});
        if (imageRef && extendToCanvas) {
            size_t width = CGImageGetWidth(imageRef);
            size_t height = CGImageGetHeight(imageRef);
            if (width == _width && height == _height) {
                CGImageRef imageRefExtended = YYCGImageCreateDecodedCopy(imageRef, YES);
                if (imageRefExtended) {
                    CFRelease(imageRef);
                    imageRef = imageRefExtended;
                    if (decoded) *decoded = YES;
                }
            } else {
                CGContextRef context = CGBitmapContextCreate(NULL, _width, _height, 8, 0, YYCGColorSpaceGetDeviceRGB(), kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst);
                if (context) {
                    CGContextDrawImage(context, CGRectMake(0, _height - height, width, height), imageRef);
                    CGImageRef imageRefExtended = CGBitmapContextCreateImage(context);
                    CFRelease(context);
                    if (imageRefExtended) {
                        CFRelease(imageRef);
                        imageRef = imageRefExtended;
                        if (decoded) *decoded = YES;
                    }
                }
            }
        }
        return imageRef;
    }
    
    if (_apngSource) {
        uint32_t size = 0;
        uint8_t *bytes = yy_png_copy_frame_data_at_index(_data.bytes, _apngSource, (uint32_t)index, &size);
        if (!bytes) return NULL;
        CGDataProviderRef provider = CGDataProviderCreateWithData(bytes, bytes, size, YYCGDataProviderReleaseDataCallback);
        if (!provider) {
            free(bytes);
            return NULL;
        }
        bytes = NULL; // hold by provider
        
        CGImageSourceRef source = CGImageSourceCreateWithDataProvider(provider, NULL);
        if (!source) {
            CFRelease(provider);
            return NULL;
        }
        CFRelease(provider);
        
        if(CGImageSourceGetCount(source) < 1) {
            CFRelease(source);
            return NULL;
        }
        
        CGImageRef imageRef = CGImageSourceCreateImageAtIndex(source, 0, (CFDictionaryRef)@{(id)kCGImageSourceShouldCache:@(YES)});
        CFRelease(source);
        if (!imageRef) return NULL;
        if (extendToCanvas) {
            CGContextRef context = CGBitmapContextCreate(NULL, _width, _height, 8, 0, YYCGColorSpaceGetDeviceRGB(), kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst); //bgrA
            if (context) {
                CGContextDrawImage(context, CGRectMake(frame.offsetX, frame.offsetY, frame.width, frame.height), imageRef);
                CFRelease(imageRef);
                imageRef = CGBitmapContextCreateImage(context);
                CFRelease(context);
                if (decoded) *decoded = YES;
            }
        }
        return imageRef;
    }
    
#if YYIMAGE_WEBP_ENABLED
    if (_webpSource) {
        WebPIterator iter;
        if (!WebPDemuxGetFrame(_webpSource, (int)(index + 1), &iter)) return NULL; // demux webp frame data
        // frame numbers are one-based in webp -----------^
        
        int frameWidth = iter.width;
        int frameHeight = iter.height;
        if (frameWidth < 1 || frameHeight < 1) return NULL;
        
        int width = extendToCanvas ? (int)_width : frameWidth;
        int height = extendToCanvas ? (int)_height : frameHeight;
        if (width > _width || height > _height) return NULL;
        
        const uint8_t *payload = iter.fragment.bytes;
        size_t payloadSize = iter.fragment.size;
        
        WebPDecoderConfig config;
        if (!WebPInitDecoderConfig(&config)) {
            WebPDemuxReleaseIterator(&iter);
            return NULL;
        }
        if (WebPGetFeatures(payload , payloadSize, &config.input) != VP8_STATUS_OK) {
            WebPDemuxReleaseIterator(&iter);
            return NULL;
        }
        
        size_t bitsPerComponent = 8;
        size_t bitsPerPixel = 32;
        size_t bytesPerRow = YYImageByteAlign(bitsPerPixel / 8 * width, 32);
        size_t length = bytesPerRow * height;
        CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Host | kCGImageAlphaPremultipliedFirst; //bgrA
        
        void *pixels = calloc(1, length);
        if (!pixels) {
            WebPDemuxReleaseIterator(&iter);
            return NULL;
        }
        
        config.output.colorspace = MODE_bgrA;
        config.output.is_external_memory = 1;
        config.output.u.RGBA.rgba = pixels;
        config.output.u.RGBA.stride = (int)bytesPerRow;
        config.output.u.RGBA.size = length;
        VP8StatusCode result = WebPDecode(payload, payloadSize, &config); // decode
        if ((result != VP8_STATUS_OK) && (result != VP8_STATUS_NOT_ENOUGH_DATA)) {
            WebPDemuxReleaseIterator(&iter);
            free(pixels);
            return NULL;
        }
        WebPDemuxReleaseIterator(&iter);
        
        if (extendToCanvas && (iter.x_offset != 0 || iter.y_offset != 0)) {
            void *tmp = calloc(1, length);
            if (tmp) {
                vImage_Buffer src = {pixels, height, width, bytesPerRow};
                vImage_Buffer dest = {tmp, height, width, bytesPerRow};
                vImage_CGAffineTransform transform = {1, 0, 0, 1, iter.x_offset, -iter.y_offset};
                uint8_t backColor[4] = {0};
                vImage_Error error = vImageAffineWarpCG_ARGB8888(&src, &dest, NULL, &transform, backColor, kvImageBackgroundColorFill);
                if (error == kvImageNoError) {
                    memcpy(pixels, tmp, length);
                }
                free(tmp);
            }
        }
        
        CGDataProviderRef provider = CGDataProviderCreateWithData(pixels, pixels, length, YYCGDataProviderReleaseDataCallback);
        if (!provider) {
            free(pixels);
            return NULL;
        }
        pixels = NULL; // hold by provider
        
        CGImageRef image = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, YYCGColorSpaceGetDeviceRGB(), bitmapInfo, provider, NULL, false, kCGRenderingIntentDefault);
        CFRelease(provider);
        if (decoded) *decoded = YES;
        return image;
    }
#endif
    
    return NULL;
}

二、使用

    //利用 CPU 操作！！！
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        //线程安全的！！！
        YYImage *image = [YYImage imageNamed:@"mew_baseline"];//不用放在主线程，YYImage线程安全的
        dispatch_async(dispatch_get_main_queue(), ^{
            //imageView 的显示当中会不会出现隐士事务的提交
            _imageView.image = image;
            NSLog(@"imageview");
        });
    });