ios - 正确裁剪和缩放 UIImage

Question

我正在尝试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，但它并不真正适合我。我得到的图像有时方向不同，或者未从中心裁剪，或者比应有的宽度更宽。

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();

必须怎样做才能得到正确的结果？

Answer 1

我建议您将此类别用于发布在 github 上的 UIImage .它们也是非常简单的类，您还可以使用它们来了解幕后的内容。