编译并运行app，结果应如下图所示:
根据控制台的输出来看，貌似识别器识别到了人脸:
Found bounds are (314.0, 243.0, 196.0, 196.0)
当前的实现中没有解决的问题:
人脸识别是在原始图像上进行的，由于原始图像的分辨率比image view要高，因此需要设置image view的content mode为aspect fit(保持纵横比的情况下缩放图片)。为了合适的绘制矩形框，需要计算image view中人脸的实际位置与尺寸 还要注意的是，CoreImage与UIView使用两种不同的坐标系统(看下图)，因此要实现一个CoreImage坐标到UIView坐标的转换。UIView坐标系:
CoreImage坐标系:
现在使用下面的代码替换detect()方法:
func detect1() {
guard let personciImage = CIImage(image: personPic.image!) else { return }
let accuracy = [CIDetectorAccuracy: CIDetectorAccuracyHigh]
let faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: nil, options: accuracy)
let faces = faceDetector?.features(in: personciImage)
// 转换坐标系
let ciImageSize = personciImage.extent.size
var transform = CGAffineTransform(scaleX: 1, y: -1)
transform = transform.translatedBy(x: 0, y: -ciImageSize.height)
for face in faces as! [CIFaceFeature] {
print("Found bounds are (face.bounds)")
// 应用变换转换坐标
var faceViewBounds = face.bounds.applying(transform)
// 在图像视图中计算矩形的实际位置和大小
let viewSize = personPic.bounds.size
let scale = min(viewSize.width / ciImageSize.width, viewSize.height / ciImageSize.height)
let offsetX = (viewSize.width - ciImageSize.width * scale) / 2
let offsetY = (viewSize.height - ciImageSize.height * scale) / 2
faceViewBounds = faceViewBounds.applying(CGAffineTransform(scaleX: scale, y: scale))
faceViewBounds.origin.x += offsetX
faceViewBounds.origin.y += offsetY
let faceBox = UIView(frame: faceViewBounds)
faceBox.layer.borderWidth = 3
faceBox.layer.borderColor = UIColor.red.cgColor
faceBox.backgroundColor = UIColor.clear
personPic.addSubview(faceBox)
if face.hasLeftEyePosition {
print("Left eye bounds are (face.leftEyePosition)")
}
if face.hasRightEyePosition {
print("Right eye bounds are (face.rightEyePosition)")
}
}
}
上述代码中，首先使用仿射变换（AffineTransform）将Core Image坐标转换为UIKit坐标，然后编写了计算实际位置与矩形视图尺寸的代码。
