正确裁剪和缩放UIImage

我试图将图像裁剪成正方形，然后将其缩放到200x200的大小。这是我使用的代码，但它并不适合我。我得到的图像有时是不同的方向，或者不是从中心裁剪出来的，或者是比应该更宽的图像。正确裁剪和缩放UIImage

float scale = _avatar.image.scale; 
UIImageOrientation orientation = _avatar.image.imageOrientation; 

if(_avatar.image.size.width < _avatar.image.size.height){ // avatar is a UIImageView 
    float startingY = (_avatar.image.size.height-_avatar.image.size.width)/2; // image is taller, determine the origin of the width-sized square, which will be the new image 
    CGImageRef imageRef = CGImageCreateWithImageInRect([_avatar.image CGImage], CGRectMake(0, startingY, _avatar.image.size.width, _avatar.image.size.width)); 
    _avatar.image = [UIImage imageWithCGImage:imageRef scale:scale orientation:orientation]; 
    CGImageRelease(imageRef); 
} else { 
    float startingX = (_avatar.image.size.width-_avatar.image.size.height)/2; // image is wider, determine the origin of the height-sized square, which will be the new image 
    CGImageRef imageRef = CGImageCreateWithImageInRect([_avatar.image CGImage], CGRectMake(startingX, 0, _avatar.image.size.height, _avatar.image.size.height)); 
    _avatar.image = [UIImage imageWithCGImage:imageRef scale:scale orientation:orientation]; 
    CGImageRelease(imageRef); 
} 

UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 200), YES, 0.0); 
[_avatar.image drawInRect:CGRectMake(0, 0, 200, 200)]; 
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext();

如何实现正确的结果？

来源

2013-08-01 nemesis

有必要吗？否则，您可以将imageview的大小设置为200 * 200并将内容模式设置为aspectfill – Iducool

这就是我需要将其上传到Web服务器。 – nemesis

我建议你使用这个类别的UIImage张贴在github。他们也是非常简单的类，你也可以使用它们来了解底层的东西。

来源

2013-08-01 13:17:55 Andrea

UIImage为您完成了所有坐标和定位技巧。所以你不应该使用UIImage对象的宽度和高度来计算正方形的坐标。您可以利用UIKit来裁剪图像。

CGFloat startingX = 0; 
CGFloat startingY = 0; 
CGFloat squareWidth; 
if(_avatar.image.size.width < _avatar.image.size.height){ // avatar is a UIImageView 
    startingY = (_avatar.image.size.height-_avatar.image.size.width)/2; // image is taller, determine the origin of the width-sized square, which will be the new image 
    squareWidth = _avatar.image.size.width; 
} else { 
    startingX = (_avatar.image.size.width-_avatar.image.size.height)/2; // image is wider, determine the origin of the height-sized square, which will be the new image 
    squareWidth = _avatar.image.size.height; 
} 

UIGraphicsBeginImageContextWithOptions(CGSizeMake(squareWidth, squareWidth), YES, 0.0); 
[_avatar.image drawAtPoint:CGPointMake(-startingX, -startingY)]; // Make an offset to draw part of the image 
UIImage *croppedImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 

UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 200), YES, 0.0); 
[croppedImage drawInRect:CGRectMake(0, 0, 200, 200)]; 
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext();

来源

2013-08-01 14:02:59 liuyaodong

正确裁剪和缩放UIImage

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