ios - 通过脸部检测面对面

我正在修改Apple SquareCam示例面部检测应用程序，以使其在写入相机胶卷之前将面部裁剪出来，而不是在面部周围绘制红色正方形。我正在使用与绘制红色正方形相同的CGRect进行裁剪。但是，行为是不同的。在纵向模式下，如果脸部位于屏幕的水平中心，则将按预期裁切脸部(红色方块原应位于相同的位置)。如果脸部偏向左侧或右侧，则似乎总是从屏幕中间进行裁切，而不是从红色正方形开始裁切。

这是苹果的原始代码:

- (CGImageRef)newSquareOverlayedImageForFeatures:(NSArray *)features
                                            inCGImage:(CGImageRef)backgroundImage
                                      withOrientation:(UIDeviceOrientation)orientation
                                          frontFacing:(BOOL)isFrontFacing
{
    CGImageRef returnImage = NULL;
    CGRect backgroundImageRect = CGRectMake(0., 0., CGImageGetWidth(backgroundImage), CGImageGetHeight(backgroundImage));
    CGContextRef bitmapContext = CreateCGBitmapContextForSize(backgroundImageRect.size);
    CGContextClearRect(bitmapContext, backgroundImageRect);
    CGContextDrawImage(bitmapContext, backgroundImageRect, backgroundImage);
    CGFloat rotationDegrees = 0.;

    switch (orientation) {
        case UIDeviceOrientationPortrait:
            rotationDegrees = -90.;
            break;
        case UIDeviceOrientationPortraitUpsideDown:
            rotationDegrees = 90.;
            break;
        case UIDeviceOrientationLandscapeLeft:
            if (isFrontFacing) rotationDegrees = 180.;
            else rotationDegrees = 0.;
            break;
        case UIDeviceOrientationLandscapeRight:
            if (isFrontFacing) rotationDegrees = 0.;
            else rotationDegrees = 180.;
            break;
        case UIDeviceOrientationFaceUp:
        case UIDeviceOrientationFaceDown:
        default:
            break; // leave the layer in its last known orientation
    }
    UIImage *rotatedSquareImage = [square imageRotatedByDegrees:rotationDegrees];

    // features found by the face detector
    for ( CIFaceFeature *ff in features ) {
        CGRect faceRect = [ff bounds];
        NSLog(@"faceRect=%@", NSStringFromCGRect(faceRect));
        CGContextDrawImage(bitmapContext, faceRect, [rotatedSquareImage CGImage]);
    }
    returnImage = CGBitmapContextCreateImage(bitmapContext);
    CGContextRelease (bitmapContext);

    return returnImage;
}

和我的替代品:

- (CGImageRef)newSquareOverlayedImageForFeatures:(NSArray *)features
                                            inCGImage:(CGImageRef)backgroundImage
                                      withOrientation:(UIDeviceOrientation)orientation
                                          frontFacing:(BOOL)isFrontFacing
{
    CGImageRef returnImage = NULL;

    //I'm only taking pics with one face. This is just for testing
    for ( CIFaceFeature *ff in features ) {
        CGRect faceRect = [ff bounds];
        returnImage = CGImageCreateWithImageInRect(backgroundImage, faceRect);
    }

    return returnImage;
}

更新*

根据Wains的输入，我尝试使代码更像原始代码，但结果是相同的:

- (NSArray*)extractFaceImages:(NSArray *)features
              fromCGImage:(CGImageRef)sourceImage
          withOrientation:(UIDeviceOrientation)orientation
              frontFacing:(BOOL)isFrontFacing
{
 NSMutableArray *faceImages = [[[NSMutableArray alloc] initWithCapacity:1] autorelease];


CGImageRef returnImage = NULL;
CGRect backgroundImageRect = CGRectMake(0., 0., CGImageGetWidth(sourceImage), CGImageGetHeight(sourceImage));
CGContextRef bitmapContext = CreateCGBitmapContextForSize(backgroundImageRect.size);
CGContextClearRect(bitmapContext, backgroundImageRect);
CGContextDrawImage(bitmapContext, backgroundImageRect, sourceImage);
CGFloat rotationDegrees = 0.;

switch (orientation) {
    case UIDeviceOrientationPortrait:
        rotationDegrees = -90.;
        break;
    case UIDeviceOrientationPortraitUpsideDown:
        rotationDegrees = 90.;
        break;
    case UIDeviceOrientationLandscapeLeft:
        if (isFrontFacing) rotationDegrees = 180.;
        else rotationDegrees = 0.;
        break;
    case UIDeviceOrientationLandscapeRight:
        if (isFrontFacing) rotationDegrees = 0.;
        else rotationDegrees = 180.;
        break;
    case UIDeviceOrientationFaceUp:
    case UIDeviceOrientationFaceDown:
    default:
        break; // leave the layer in its last known orientation
}

// features found by the face detector
for ( CIFaceFeature *ff in features ) {
    CGRect faceRect = [ff bounds];

    NSLog(@"faceRect=%@", NSStringFromCGRect(faceRect));

    returnImage = CGBitmapContextCreateImage(bitmapContext);
    returnImage = CGImageCreateWithImageInRect(returnImage, faceRect);
    UIImage *clippedFace = [UIImage imageWithCGImage:returnImage];
    [faceImages addObject:clippedFace];
}

CGContextRelease (bitmapContext);

return faceImages;

}

我拍了三张照片并记录了这些结果的faceRect。

拍摄的脸部位于设备左边缘附近。捕获图像完全错过了右边的脸:
faceRect = {{972，43.0312}，{673.312，673.312}}

拍摄的脸部位于设备中间的照片。拍摄图像好:
faceRect = {{1060.59，536.625}，{668.25，668.25}}

所拍照片的脸部靠近设备的右边缘。捕获图像完全错过了左脸:
faceRect = {{982.125，999.844}，{804.938，804.938}}

因此看来“x”和“y”是相反的。我将设备纵向放置，但faceRect似乎是基于横向的。但是，我无法弄清楚Apple原始代码的哪一部分是造成这一问题的原因。该方法中的方向代码似乎仅影响红场叠加图像本身。

最佳答案

您应该保留所有原始代码，并在返回之前添加一行(通过调整将图像生成放入循环中，因为您只裁剪了第一张脸):

returnImage = CGImageCreateWithImageInRect(returnImage, faceRect);

这允许以正确的方向渲染图像，这意味着面部rect将位于正确的位置。

关于ios - 通过脸部检测面对面，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/17266910/