快速将大图保存到本地

       碰到一个问题：如何快速的批量保存iphone相册中的图片（原始的大图，分辨率高）到本地？

保存图片到本地，首先得拿到这个图片：alAsset.defaultRepresentation.fullResolutionImage.但是图片太大了，大批量的保存取这个图片就得花很长的时间，再转NSData存入本地又得很久，所以这种读写方式是不行的。

      我google了一下，在stack overflow找到了方法：点击打开链接 。

      我把实现的方法贴一下（包括大图和缩略图）：

 

//reading out the orginal images

    for (int j=0; j<[assetArray count]; j++) {



    ALAssetRepresentation *representation = [[assetArray objectAtIndex:j] defaultRepresentation];

    NSString* filename = [documentPath stringByAppendingPathComponent:[representation filename]];



    [[NSFileManager defaultManager] createFileAtPath:filename contents:nil attributes:nil];

    NSOutputStream *outPutStream = [NSOutputStream outputStreamToFileAtPath:filename append:YES];

    [outPutStream open];



    long long offset = 0;

    long long bytesRead = 0;



    NSError *error;

    uint8_t * buffer = malloc(131072);

    while (offset<[representation size] && [outPutStream hasSpaceAvailable]) {

        bytesRead = [representation getBytes:buffer fromOffset:offset length:131072 error:&error];

        [outPutStream write:buffer maxLength:bytesRead];

        offset = offset+bytesRead;

    }

    [outPutStream close];

    free(buffer);

}





//reading out the fullScreenImages and thumbnails

for (int j=0; j<[assetArray count]; j++) 

{

    @autoreleasepool

    {



        ALAsset *asset = [assetArray objectAtIndex:j];



         NSString *orgFilename = [representation filename];

         NSString *filenameFullScreen = [NSString stringWithFormat:@"%@_fullscreen.png",[orgFilename stringByDeletingPathExtension]]

         NSString* pathFullScreen = [documentPath stringByAppendingPathComponent:filenameFullScreen];



         CGImageRef imageRefFullScreen = [[asset defaultRepresentation] fullScreenImage];

         UIImage *imageFullScreen = [UIImage imageWithCGImage:imageRefFullScreen];

         NSData *imageDataFullScreen = UIImagePNGRepresentation(imageFullScreen);

         [imageDataFullScreen writeToFile:pathFullScreen atomically:YES];



         NSString *filenameThumb = [NSString stringWithFormat:@"%@_thumb.png",[orgFilename stringByDeletingPathExtension]]

         NSString* pathThumb = [documentPath stringByAppendingPathComponent:filenameThumb];



         CGImageRef imageRefThumb = [asset thumbnail];

         UIImage *imageThumb = [UIImage imageWithCGImage:imageRefThumb];

         NSData *imageDataThumb = UIImagePNGRepresentation(imageThumb);

         [imageDataThumb writeToFile:pathThumb atomically:YES];



    }

}

 

参考：http://stackoverflow.com/questions/9973259/what-is-the-correct-way-to-import-save-photos-from-iphone-album