如何鏡像來自UIImagePickerController的UIImage圖片

Question

我在弄清楚是否有任何方法來鏡像圖像。例如，拍攝某人臉部的照片，然後將其切成兩半，並顯示他們的每張臉的鏡像。在CGAffineTransform函數中似乎沒有這樣的技巧。圖形專家請幫忙!!!

Answer 1

這裏的基本「技巧」是對因子爲-1的X軸或Y軸使用縮放變換。例如，你可以使用它來創建一個「繞水平軸翻轉」改造：

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

然後你可以設置一個UIImageView的transform屬性翻轉分配的圖像，或與其他串接它轉換爲做更復雜的效果。爲了獲得您描述的確切效果，您可能需要編寫一些自定義繪圖代碼，將原始圖像繪製到上下文中，然後將翻轉的一半覆蓋在上面。這在Core Graphics中相對比較簡單。

Answer 2

如果你只打算支持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

你可能會想，爲什麼與悍然長switch語句煩惱呢？

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

如果你看看枚舉，你可以看到，模運算會做：

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 
}; 

但是這個代碼是太聰明瞭。您應該使用顯式switch語句來編寫函數。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; 
    } 
} 

而且使用這樣的功能：

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

我已經添加了問號表示可疑，臭代碼。類似於The Practice of Programming

Answer 4

上面的答案都不是，迴應了映射圖像一半而不是翻轉整個圖像的部分問題。混合溶液導致可能會作爲一個類別如UIImage的+鏡像使用下面的示例功能：

(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; 
}