iphone - 尝试从图像 I/O 创建 AspectRatioThumbnail 时出错

Question

ALAsset我正在尝试从iOS5 之前的版本创建纵横比缩略图（ALAssetDefaultRepresentation aspectRatioThumbnail直到 ios5 才实现）。我有以下代码，由于某种原因它给了我一个错误：

CGImageRef imref;
    NSURL* url = [self.photoAsset.defaultRepresentation url];
    NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:
                       (id)kCFBooleanTrue, kCGImageSourceShouldAllowFloat,
                       (id)kCFBooleanTrue, kCGImageSourceCreateThumbnailWithTransform,
                       (id)kCFBooleanTrue, kCGImageSourceCreateThumbnailFromImageAlways,
                       [NSNumber numberWithInteger:1024], kCGImageSourceThumbnailMaxPixelSize, nil];
    CGImageSourceRef src = CGImageSourceCreateWithURL((CFURLRef)url, NULL);
    imref = CGImageSourceCreateThumbnailAtIndex(src, 0, (CFDictionaryRef) dictionary);

具体来说，我得到：

ImageIO: <ERROR>  CGImageSourceCreateWithURL CFURLCreateDataAndPropertiesFromResource failed with error code -11.ImageIO: <ERROR>  CGImageSourceCreateThumbnailAtIndex image source parameter is nil

有谁知道发生了什么？

Answer 1

问题url在于您要传递以创建“ src”，检查是否url有效并且此 url 中存在一些图像。