CIDetector和UIImagePickerController

Question

我正在尝试实现内置的iOS 5人脸检测应用程序接口。我正在使用UIImagePickerController的一个实例来允许用户拍照，然后我尝试使用CIDetector来检测面部特征。不幸的是，featuresInImage总是返回一个大小为0的数组。

代码如下：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
UIImage* picture = [info objectForKey:UIImagePickerControllerOriginalImage];

NSNumber *orientation = [NSNumber numberWithInt:
                         [picture imageOrientation]];
NSDictionary *imageOptions =
[NSDictionary dictionaryWithObject:orientation
                            forKey:CIDetectorImageOrientation];

CIImage *ciimage = [CIImage imageWithCGImage:[picture CGImage]
                                     options:imageOptions];


NSDictionary *detectorOptions =
[NSDictionary dictionaryWithObject:CIDetectorAccuracyLow
                            forKey:CIDetectorAccuracy];
CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeFace
                                          context:nil
                                          options:detectorOptions];

NSArray *features = [detector featuresInImage:ciimage];
NSLog(@"Feature size: %d", features.count);
}

这将始终返回0个功能。但是，如果我使用应用程序内置文件中的UIImage，人脸检测效果会很好。

我使用的是这个Pragmatic Bookshelf article中的代码。

无论如何，我认为错误是当我将UIImage从相机转换为CIImage时，但它可以是任何东西。

Answer 1

@tonyc您的解决方案仅适用于特定情况，即"UIImageOrientationRight“。问题来自于UIImage和CIDetectorImageOrientation中的方向不同。来自iOS文档：

CIDetectorImageOrientation

用于指定要检测其特征的图像的显示方向的键。此键是一个NSNumber对象，其值与TIFF和EXIF规范定义的值相同；值的范围从1到8。该值指定图像的原点(0,0)所在的位置。如果不存在，则默认值为1，这意味着图像的原点是左上角。有关每个值指定的图像原点的详细信息，请参见kCGImagePropertyOrientation。

在iOS 5.0及更高版本中可用。

在CIDetector.h中声明。

所以现在的问题是这两个方向之间的转换，这是我在代码中做的，我测试了它，它对所有方向都有效：

int exifOrientation;
switch (self.image.imageOrientation) {
    case UIImageOrientationUp:
        exifOrientation = 1;
        break;
    case UIImageOrientationDown:
        exifOrientation = 3;
        break;
    case UIImageOrientationLeft:
        exifOrientation = 8;
        break;
    case UIImageOrientationRight:
        exifOrientation = 6;
        break;
    case UIImageOrientationUpMirrored:
        exifOrientation = 2;
        break;
    case UIImageOrientationDownMirrored:
        exifOrientation = 4;
        break;
    case UIImageOrientationLeftMirrored:
        exifOrientation = 5;
        break;
    case UIImageOrientationRightMirrored:
        exifOrientation = 7;
        break;
    default:
        break;
}

NSDictionary *detectorOptions = @{ CIDetectorAccuracy : CIDetectorAccuracyHigh }; // TODO: read doc for more tuneups
CIDetector *faceDetector = [CIDetector detectorOfType:CIDetectorTypeFace context:nil options:detectorOptions];

NSArray *features = [faceDetector featuresInImage:[CIImage imageWithCGImage:self.image.CGImage]
                                          options:@{CIDetectorImageOrientation:[NSNumber numberWithInt:exifOrientation]}];

Answer 2

果然，在花了一天的时间研究这个问题并被难住之后，我在发布这篇文章一个小时后找到了解决方案。

我最终注意到人脸检测在风景中起作用，但在肖像中不起作用。

事实证明我需要这些选项：

NSDictionary *imageOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:6]
                                                         forKey:CIDetectorImageOrientation];
NSArray *features = [detector featuresInImage:ciimage options:imageOptions];

Answer 3

Swift 3版本

var exifOrientation : Int
switch (inputImage.imageOrientation)
{
case UIImageOrientation.up:
    exifOrientation = 1;
case UIImageOrientation.down:
    exifOrientation = 3;
case UIImageOrientation.left:
    exifOrientation = 8;
case UIImageOrientation.right:
    exifOrientation = 6;
case UIImageOrientation.upMirrored:
    exifOrientation = 2;
case UIImageOrientation.downMirrored:
    exifOrientation = 4;
case UIImageOrientation.leftMirrored:
    exifOrientation = 5;
case UIImageOrientation.rightMirrored:
    exifOrientation = 7;
}

let ciImage = CIImage(cgImage: inputImage.cgImage!)
let options = [CIDetectorAccuracy: CIDetectorAccuracyHigh]
let faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: nil, options: options)!
let faces = faceDetector.features(in: ciImage, options:["CIDetectorImageOrientation":exifOrientation])