import <ImageIO/ImageIO.h>

/**
 从Image Sources中获取缩略图

 @param imageSize 缩略图的大小
 */
- (void)getThumbnailImageFromImageSourceWithSize:(int)imageSize {
    
    
    CGImageRef thumbImage;
    CGImageSourceRef imageSource;
    CFDictionaryRef imageOption;
    
    
    CFStringRef imageKeys[3];
    CFTypeRef imageValues[3];
    
    
    //缩略图尺寸
    CFNumberRef thumbSize;
    
    
    imageSource = CGImageSourceCreateWithURL((CFURLRef)imageFileURL, NULL);
    if (imageSource == nil) {
        return;
    }
    
    
    //创建缩略图等比缩放大小，会根据长宽值比较大的作为imageSize进行缩放
    thumbSize = CFNumberCreate(NULL, kCFNumberIntType, &imageSize);
    
    
    imageKeys[0] = kCGImageSourceCreateThumbnailWithTransform;
    imageValues[0] = (CFTypeRef)kCFBooleanTrue;
    
    imageKeys[1] = kCGImageSourceCreateThumbnailFromImageIfAbsent;
    imageValues[1] = (CFTypeRef)kCFBooleanTrue;
  
    //缩放键值对
    imageKeys[2] = kCGImageSourceThumbnailMaxPixelSize;
    imageValues[2] = (CFTypeRef)thumbSize;
    
    
    imageOption = CFDictionaryCreate(NULL, (const void **) imageKeys,
                                      (const void **) imageValues, 3,
                                      &kCFTypeDictionaryKeyCallBacks,
                                      &kCFTypeDictionaryValueCallBacks);
    
    //获取缩略图
    thumbImage = CGImageSourceCreateThumbnailAtIndex(imageSource, 0, imageOption);
    
    
    CFRelease(imageOption);
    CFRelease(imageSource);
    CFRelease(thumbSize);
    
    
    //显示缩略图
    UIImage *imageResult = [UIImage imageWithCGImage:thumbImage];
    UIImageView *imageView=[[UIImageView alloc]initWithFrame:CGRectMake(0, 300, 320, 200)];
    [self.view addSubview:imageView];
    imageView.image = imageResult;
    
    
    //将缩略图保存到本地，查看大小，目的查看缩略图的大小
    NSArray *paths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *imagePath=[[paths lastObject] stringByAppendingFormat:@"/test_thumb.jpg"];
    
    [UIImageJPEGRepresentation(imageResult, 1) writeToFile:imagePath atomically:YES];
    
    NSLog(@"imagePath  %@",imagePath);
    
    
}

/**
 从Image Sources中创建一个图像
 @param imageFileURL 图片的本地路径
 */
- (void)getImageFromImageSource:(NSString *)imageFileURL {
    
    CGImageRef cgimage;
    CGImageSourceRef imageSource;
    CFDictionaryRef imageOptions;
    
    
    
    //键值对，为创建 CFDictionaryRef 做准备
    CFStringRef imageKeys[2];
    CFTypeRef imageValues[2];
    
    //缓存
    imageKeys[0] = kCGImageSourceShouldCache;
    imageValues[0] = (CFTypeRef)kCFBooleanTrue;
    
    //float-point
    imageKeys[1] = kCGImageSourceShouldAllowFloat;
    imageValues[1] = (CFTypeRef)kCFBooleanTrue;
    
    
    //设置参数，为创建 CGImageSourceRef 对象做准备
    imageOptions = CFDictionaryCreate(NULL, (const void **)imageKeys, (const void **)imageValues, 2, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    
    
    //创建 CGImageSourceRef 对象，URL为图片的本地路径，imageOptions 为参数的设置
    imageSource = CGImageSourceCreateWithURL((CFURLRef)imageFileURL, (CFDictionaryRef)imageOptions);
    
    if (imageSource == nil) {
        return;
    }
    
    //从 CGImageSourceRef 中获取 CGImageRef 对象
    cgimage = CGImageSourceCreateImageAtIndex(imageSource, 0, NULL);
    
    
    CFRelease(imageOptions);
    CFRelease(imageSource);
    
    
    //从 CGImageRef 中获取 UIImage 对象
    UIImage *imageResult=[UIImage imageWithCGImage:cgimage];
    
    
    UIImageView *imageView=[[UIImageView alloc]initWithFrame:CGRectMake(0, 20, 320, 200)];
    [self.view addSubview:imageView];
    imageView.image = imageResult;

}