ios - 如何以编程方式调整图像像素大小

Question

我正在使用 Facebook 创建应用程序。如果我正在尝试将照片上传到 Facebook 意味着我收到以下消息任何解决该问题的想法

“为 OG 操作提供的用户生成的照片在两个维度上必须至少为 480 像素”

Answer 1

我使用如下函数来获取任意大小的图像。原始图片应该比你想要的大。(ps:你可以尝试小图片)

+ (UIImage *)thumbnailWithImageWithoutScale:(UIImage *)image size:(CGSize)wantSize
{
    UIImage * targetImage;
    if (nil == image) {
        targetImage = nil;
    }else{
        CGSize size = image.size;
        CGRect rect;
        if (wantSize.width/wantSize.height > size.width/size.height) {
            rect.size.width = wantSize.height*size.width/size.height;
            rect.size.height = wantSize.height;
            rect.origin.x = (wantSize.width - rect.size.width)/2;
            rect.origin.y = 0;
        } else{
            rect.size.width = wantSize.width;
            rect.size.height = wantSize.width*size.height/size.width;
            rect.origin.x = 0;
            rect.origin.y = (wantSize.height - rect.size.height)/2;
        }
        UIGraphicsBeginImageContext(wantSize);
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSetFillColorWithColor(context, [[UIColor clearColor] CGColor]);
        UIRectFill(CGRectMake(0, 0, wantSize.width, wantSize.height));//clear background
        [image drawInRect:rect];
        targetImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    return targetImage;
}