iphone - 以编程方式将 UIImage 比率更改为 iphone 中的 fb 封面

Question

我正在从图片选择器中挑选一张图片，然后我想更改该图片作为 Facebook 封面的比例。我有一张图片，假设它的分辨率为 640 宽和 480 高，我想将其更改为 facebook 封面(851 像素宽和 315 像素高)我将如何在 iphone 中以编程方式执行此操作检查这个link封面图片详情谢谢。

Answer 1

 Use this Method to Resize the image according to the given content mode, taking into account the image's orientation...

- (UIImage *)resizedImageWithContentMode:(UIViewContentMode)contentMode bounds:(CGSize)bounds
                interpolationQuality:(CGInterpolationQuality)quality {

CGFloat horizontalRatio = bounds.width / self.size.width;
CGFloat verticalRatio = bounds.height / self.size.height;
CGFloat ratio;

switch (contentMode) {
    case UIViewContentModeScaleAspectFill:
        ratio = MAX(horizontalRatio, verticalRatio);
        break;

    case UIViewContentModeScaleAspectFit:
        ratio = MIN(horizontalRatio, verticalRatio);
        break;

    default:
        [NSException raise:NSInvalidArgumentException format:@"Unsupported content mode:  %d", contentMode];
}

CGSize newSize = CGSizeMake(self.size.width * ratio, self.size.height * ratio);

return [self resizedImage:newSize interpolationQuality:quality];

并转到此链接了解更多详情，Resizing Uiimage in right way .