需求:UIImage根据屏幕宽度按照自己本身比例改变高度
上代码,为UIImage创建一个Category
代码如下 | 复制代码 |
#import"UIImage+UIImageExtras.h" @implementationUIImage (UIImageExtras) - (UIImage *)imageByScalingToSize:(CGSize)targetSize { UIImage *sourceImage = self; UIImage *newImage = nil; CGSize imageSize = sourceImage.size; CGFloat width = imageSize.width; CGFloat height = imageSize.height; CGFloat targetWidth = targetSize.width; CGFloat targetHeight = targetSize.height; CGFloat scaleFactor =0.0; CGFloat scaledWidth = targetWidth; CGFloat scaledHeight = targetHeight; CGPoint thumbnailPoint = CGPointMake(0.0,0.0); if(CGSizeEqualToSize(imageSize, targetSize) ==NO) { CGFloat widthFactor = targetWidth / width; CGFloat heightFactor = targetHeight / height; if(widthFactor < heightFactor) scaleFactor = widthFactor; else scaleFactor = heightFactor; scaledWidth = width * scaleFactor; scaledHeight = height * scaleFactor; // center the image if(widthFactor < heightFactor) {
thumbnailPoint.y = (targetHeight - scaledHeight) *0.5; }elseif(widthFactor > heightFactor) { thumbnailPoint.x = (targetWidth - scaledWidth) *0.5; } } // this is actually the interesting part: UIGraphicsBeginImageContext(targetSize); CGRect thumbnailRect = CGRectZero; thumbnailRect.origin = thumbnailPoint; thumbnailRect.size.width = scaledWidth; thumbnailRect.size.height = scaledHeight; [sourceImage drawInRect:thumbnailRect]; newImage =UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); if(newImage == nil) NSLog(@"could not scale image"); returnnewImage ; } @end |
在需要使用的地方import然后使用
代码如下 | 复制代码 |
CGSize size = image.size; image = [image imageByScalingToSize:CGSizeMake([UIScreen mainScreen].bounds.size.width,[UIScreen mainScreen].bounds.size.width * (size.height / size.width))]; self.imageview.image = image; |
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