iphone缩略图处理

-(UIImage * ) generatePhotoThumbnail: (UIImage * ) image {
    // Create a thumbnail version of the image for the event object.
    CGSize size = image.size;
    CGSize croppedSize;
    CGFloat ratio = 64.0; //这个是设置转换后图片的尺寸大小
    CGFloat offsetX = 0.0;
    CGFloat offsetY = 0.0;

    // check the size of the image, we want to make it
    // a square with sides the size of the smallest dimension
    if (size.width > size.height) {
        offsetX = (size.height - size.width) / 2;
        croppedSize = CGSizeMake(size.height, size.height);
    } else {
        offsetY = (size.width - size.height) / 2;
        croppedSize = CGSizeMake(size.width, size.width);
    }

    // Crop the image before resize
    CGRect clippedRect = CGRectMake(offsetX * -1, offsetY * -1, croppedSize.width, croppedSize.height);
    CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], clippedRect);
    // Done cropping
    // Resize the image
    CGRect rect = CGRectMake(0.0, 0.0, ratio, ratio);

    UIGraphicsBeginImageContext(rect.size);
    [
        [UIImage imageWithCGImage: imageRef] drawInRect: rect];
    UIImage * thumbnail = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    // Done Resizing
    return thumbnail;
}

转载自：http://blog.sina.com.cn/s/blog_699ebf3d0100ob8h.html