以编程方式在iphone中将UIImage比率更改为fb封面

Posted 2023-03-17

【中文标题】以编程方式在iphone中将UIImage比率更改为fb封面

【英文标题】：Change UIImage ratio to fb cover in iphone Programmatically

【发布时间】：2012-12-02 20:23:46

【问题描述】：

我正在从图像选择器中选择一个图像，然后我想将该图像的比例更改为 facebook 封面。我有一张图像，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 查看此link 了解封面图片详情 谢谢。

【参考方案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];

点击此链接了解更多详情，Resizing Uiimage in right way。

【讨论】：

我将在 contentMode 中传递什么？

UIViewContentMode 指定视图在大小变化时如何调整其内容。 typedef enum UIViewContentModeScaleToFill, UIViewContentModeScaleAspectFit, UIViewContentModeScaleAspectFit, UIViewContentModeRedraw, UIViewContentModeCenter, UIViewContentModeTop, UIViewContentModeBottom, UIViewContentModeLeft, UIViewContentModeRight, UIViewContentModeTopLeft, UIViewContentModeTopRight, UIViewContentModeBottomLeft, UIViewContentModeBottomRight,

苹果文档在这里：developer.apple.com/library/ios/#documentation/UIKit/Reference/…