如何从UIImagePickerController镜像UIImage图片

Question

我想弄清楚是否有任何方法来镜像图像.例如,拍摄某人脸部的照片,然后将其切成两半,并显示每个镜像的脸部样子.在CGAffineTransform函数中似乎没有这样的技巧.图形专家请帮忙!!!

Answer 1

这里的基本"技巧"是使用关于X或Y轴的缩放变换,因子为-1.例如,您可以使用它来创建"绕水平轴翻转"变换:

CGAffineTransform transform = CGAffineTransformScale(transform, -1, 1);

然后,您可以transform在a上设置属性UIImageView以翻转指定的图像,或者将其与另一个转换连接以执行更复杂的效果.为了获得您描述的确切效果,您可能需要编写一些自定义绘图代码以将原始图像绘制到上下文中,然后将翻转的一半覆盖在其上面.这在Core Graphics中相对简单.

Answer 2

如果您只打算支持4.0+

UIImageOrientation flippedOrientation = UIImageOrientationUpMirrored;
switch (image.imageOrientation) {
  case UIImageOrientationUp: break;
  case UIImageOrientationDown: flippedOrientation = UIImageOrientationDownMirrored; break;
  // ...
}
UIImage * flippedImage = [UIImage imageWithCGImage:image.CGImage scale:image.scale orientation:flippedOrientation];

Answer 3

你可能会想,为什么要烦恼这个令人发指的长切换声明呢？

? UIImage *flip = [UIImage imageWithCGImage:image.CGImage   
?                                     scale:image.scale
?                               orientation:(image.imageOrientation + 4) % 8];

如果你看一下枚举,你可以看到模运算会做:

typedef NS_ENUM(NSInteger, UIImageOrientation) {
    UIImageOrientationUp,            // default orientation
    UIImageOrientationDown,          // 180 deg rotation
    UIImageOrientationLeft,          // 90 deg CCW
    UIImageOrientationRight,         // 90 deg CW
    UIImageOrientationUpMirrored,    // as above but image mirrored along other axis. horizontal flip
    UIImageOrientationDownMirrored,  // horizontal flip
    UIImageOrientationLeftMirrored,  // vertical flip
    UIImageOrientationRightMirrored, // vertical flip
};

但是这段代码太聪明了.您应该编写一个带有显式switch语句的函数.例如

UIImageOrientation mirroredImageOrientation(UIImageOrientation orientation) {
    switch(orientation) {
        case UIImageOrientationUp: return UIImageOrientationUpMirrored;
        case UIImageOrientationDown: return UIImageOrientationDownMirrored;
        case UIImageOrientationLeft: return UIImageOrientationLeftMirrored;
        case UIImageOrientationRight: return UIImageOrientationRightMirrored;
        case UIImageOrientationUpMirrored: return UIImageOrientationUp;
        case UIImageOrientationDownMirrored: return UIImageOrientationDown;
        case UIImageOrientationLeftMirrored: return UIImageOrientationLeft;
        case UIImageOrientationRightMirrored: return UIImageOrientationRight;
        default: return orientation;
    }
}

并使用这样的功能:

UIImage *flip = [UIImage imageWithCGImage:image.CGImage   
                                    scale:image.scale
                              orientation:mirroredImageOrientation(image.imageOrientation)];

我添加了问号来表示可疑的,有臭味的代码.类似于编程实践

Answer 4

上面的答案都没有回应问题的部分,这部分镜像反映了图像的一半而没有翻转整个图像.混合解决方案会产生以下示例函数,您可以将其用作UIImage + Mirroring等类别:

(UIImage *) horizontalMirror {
    UIImageOrientation flippedOrientation = UIImageOrientationUpMirrored;
    switch (self.imageOrientation) {
        case UIImageOrientationUp: break;
        case UIImageOrientationDown: flippedOrientation = UIImageOrientationDownMirrored; break;
    }
    UIImage * flippedImage = [UIImage imageWithCGImage:self.CGImage scale:1.0 orientation:flippedOrientation];

    CGImageRef inImage = self.CGImage;
    CGContextRef ctx = CGBitmapContextCreate(NULL,
                                             CGImageGetWidth(inImage),
                                             CGImageGetHeight(inImage),
                                             CGImageGetBitsPerComponent(inImage),
                                             CGImageGetBytesPerRow(inImage),
                                             CGImageGetColorSpace(inImage),
                                             CGImageGetBitmapInfo(inImage)
                                             );
    CGRect cropRect = CGRectMake(flippedImage.size.width/2, 0, flippedImage.size.width/2, flippedImage.size.height);
    CGImageRef TheOtherHalf = CGImageCreateWithImageInRect(flippedImage.CGImage, cropRect);
    CGContextDrawImage(ctx, CGRectMake(0, 0, CGImageGetWidth(inImage), CGImageGetHeight(inImage)), inImage);

    CGAffineTransform transform = CGAffineTransformMakeTranslation(flippedImage.size.width, 0.0);
    transform = CGAffineTransformScale(transform, -1.0, 1.0);
    CGContextConcatCTM(ctx, transform);

    CGContextDrawImage(ctx, cropRect, TheOtherHalf);

    CGImageRef imageRef = CGBitmapContextCreateImage(ctx);
    CGContextRelease(ctx);
    UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);

    return finalImage;
}

Answer 5

使用更简单：

UIImage(assetIdentifier: .myIcon)?.withHorizontallyFlippedOrientation()