SDWebImage研究2

NSData+ImageContentType
画像のタイプを取得し、実際に画像のタイプを取得する方法は、画像の最初のバイトの内容を取得することであり、最初のバイトは画像のタイプである.

+ (NSString *)sd_contentTypeForImageData:(NSData *)data {
    uint8_t c;
    [data getBytes:&c length:1];
    switch (c) {
        case 0xFF:
            return @"image/jpeg";
        case 0x89:
            return @"image/png";
        case 0x47:
            return @"image/gif";
        case 0x49:
        case 0x4D:
            return @"image/tiff";
        case 0x52:
            // R as RIFF for WEBP
            if ([data length] < 12) {
                return nil;
            }

            NSString *testString = [[NSString alloc] initWithData:[data subdataWithRange:NSMakeRange(0, 12)] encoding:NSASCIIStringEncoding];
            if ([testString hasPrefix:@"RIFF"] && [testString hasSuffix:@"WEBP"]) {
                return @"image/webp";
            }

            return nil;
    }
    return nil;
}

UIImage+GIF
イメージをgif形式の画像に戻してイメージをNSDataに変換し、コードでgif画像に何枚の画像があるかを取得します.

CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);

   size_t count = CGImageSourceGetCount(source);

gifの画像をそれぞれ取り出し、配列を入れます

NSMutableArray *images = [NSMutableArray array];

        NSTimeInterval duration = 0.0f;

        for (size_t i = 0; i < count; i++) {
            CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);
            if (!image) {
                continue;
            }

            duration += [self sd_frameDurationAtIndex:i source:source];

            [images addObject:[UIImage imageWithCGImage:image scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp]];

            CGImageRelease(image);
        }

gif 2枚の画像間の間隔を取得

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 13.0px Menlo; color: #e7e8eb}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 13.0px Menlo; color: #29a09f}p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; font: 13.0px Menlo; color: #e7e8eb; min-height: 15.0px}p.p4 {margin: 0.0px 0.0px 0.0px 0.0px; font: 13.0px Menlo; color: #51c34f}p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 13.0px Menlo; color: #6544e9}span.s1 {font-variant-ligatures: no-common-ligatures}span.s2 {font-variant-ligatures: no-common-ligatures; color: #e12da0}span.s3 {font-variant-ligatures: no-common-ligatures; color: #29a09f}span.s4 {font-variant-ligatures: no-common-ligatures; color: #00aaa3}span.s5 {font-variant-ligatures: no-common-ligatures; color: #e7e8eb}span.s6 {font-variant-ligatures: no-common-ligatures; color: #51c34f}span.s7 {font-variant-ligatures: no-common-ligatures; color: #6544e9}

+ (float)sd_frameDurationAtIndex:(NSUInteger)index source:(CGImageSourceRef)source {
    float frameDuration = 0.1f;
    CFDictionaryRef cfFrameProperties = CGImageSourceCopyPropertiesAtIndex(source, index, nil);
    NSDictionary *frameProperties = (__bridge NSDictionary *)cfFrameProperties;
    NSDictionary *gifProperties = frameProperties[(NSString *)kCGImagePropertyGIFDictionary];

    NSNumber *delayTimeUnclampedProp = gifProperties[(NSString *)kCGImagePropertyGIFUnclampedDelayTime];
    if (delayTimeUnclampedProp) {
        frameDuration = [delayTimeUnclampedProp floatValue];
    }
    else {

        NSNumber *delayTimeProp = gifProperties[(NSString *)kCGImagePropertyGIFDelayTime];
        if (delayTimeProp) {
            frameDuration = [delayTimeProp floatValue];
        }
    }

    // Many annoying ads specify a 0 duration to make an image flash as quickly as possible.
    // We follow Firefox's behavior and use a duration of 100 ms for any frames that specify
    // a duration of <= 10 ms. See  and 
    // for more information.

    if (frameDuration < 0.011f) {
        frameDuration = 0.100f;
    }

    CFRelease(cfFrameProperties);
    return frameDuration;
}

最後に取得したピクチャ配列をgifピクチャに再結合する

if (!duration) {
            duration = (1.0f / 10.0f) * count;
        }

        animatedImage = [UIImage animatedImageWithImages:images duration:duration];

+ (UIImage *)sd_animatedGIFWithData:(NSData *)data {
    if (!data) {
        return nil;
    }

    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);

    size_t count = CGImageSourceGetCount(source);

    UIImage *animatedImage;

    if (count <= 1) {
        animatedImage = [[UIImage alloc] initWithData:data];
    }
    else {
        NSMutableArray *images = [NSMutableArray array];

        NSTimeInterval duration = 0.0f;

        for (size_t i = 0; i < count; i++) {
            CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);
            if (!image) {
                continue;
            }

            duration += [self sd_frameDurationAtIndex:i source:source];

            [images addObject:[UIImage imageWithCGImage:image scale:[UIScreen mainScreen].scale orientation:UIImageOrientationUp]];

            CGImageRelease(image);
        }

        if (!duration) {
            duration = (1.0f / 10.0f) * count;
        }

        animatedImage = [UIImage animatedImageWithImages:images duration:duration];
    }

    CFRelease(source);

    return animatedImage;
}

UIImage+MultiFormat
主に異なるフォーマットのピクチャを再結合し、gifのピクチャはgifで結合し、一般的なピクチャはピクチャ方位に応じて設定してピクチャを再設定する
画像の方向

+(UIImageOrientation)sd_imageOrientationFromImageData:(NSData *)imageData {
    UIImageOrientation result = UIImageOrientationUp;
    CGImageSourceRef imageSource = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);
    if (imageSource) {
        CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, NULL);
        if (properties) {
            CFTypeRef val;
            int exifOrientation;
            val = CFDictionaryGetValue(properties, kCGImagePropertyOrientation);
            if (val) {
                CFNumberGetValue(val, kCFNumberIntType, &exifOrientation);
                result = [self sd_exifOrientationToiOSOrientation:exifOrientation];
            } // else - if it's not set it remains at up
            CFRelease((CFTypeRef) properties);
        } else {
            //NSLog(@"NO PROPERTIES, FAIL");
        }
        CFRelease(imageSource);
    }
    return result;
}
+ (UIImageOrientation) sd_exifOrientationToiOSOrientation:(int)exifOrientation {
    UIImageOrientation orientation = UIImageOrientationUp;
    switch (exifOrientation) {
        case 1:
            orientation = UIImageOrientationUp;
            break;

        case 3:
            orientation = UIImageOrientationDown;
            break;

        case 8:
            orientation = UIImageOrientationLeft;
            break;

        case 6:
            orientation = UIImageOrientationRight;
            break;

        case 2:
            orientation = UIImageOrientationUpMirrored;
            break;

        case 4:
            orientation = UIImageOrientationDownMirrored;
            break;

        case 5:
            orientation = UIImageOrientationLeftMirrored;
            break;

        case 7:
            orientation = UIImageOrientationRightMirrored;
            break;
        default:
            break;
    }
    return orientation;
}