选取相片后assets-library的转化

Asset URL不能转化为image。当用ALAsset获取

+ (UIImage *)fullResolutionImageFromALAsset:(ALAsset *)asset
{
    ALAssetRepresentation *assetRep = [asset defaultRepresentation];
    CGImageRef imgRef = [assetRep fullResolutionImage];
    UIImage *img = [UIImage imageWithCGImage:imgRef
                                       scale:assetRep.scale
                                 orientation:(UIImageOrientation)assetRep.orientation];
    return img;
}

另使用此库需注意，iOS4、5需向用户申请GPS权限才可访问照片。iOS6下申请相册访问权限才可访问照片。