UIImage 重绘图片大小

// 添加 UIImage 的分类 ResizeUIImage
@implementation UIImage (ResizeUIImage)

/**
 重绘图片大小
 @param size 要得到的图片的尺寸大小
 @return    得到的指定尺寸大小的图片
 */
- (UIImage *)resizeImageToSize:(CGSize)size {
    // change from UIGraphicsBeginImageContext(size) to suit scale > 1
    UIGraphicsBeginImageContextWithOptions(size, false, 0);
    [self drawInRect:CGRectMake(0, 0, size.width, size.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

@end

// 重新设置图片的大小
image = [image resizeImageToSize:CGSizeMake(100, 200)];