版本記錄

前言

人臉識別是圖像識別技術中的一種，廣泛的應用于很多領域，接下來這幾篇我們就一起來研究幾種關于人臉識別的技術。

基于CoreImage的人臉識別技術

CoreImage是蘋果提供的原生API，它有人臉識別的接口，可以實現人臉的識別，支持對圖像中多個人臉的識別。

代碼實現

下面我們一起看一下代碼。

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, strong) UIImageView *pictureImageView;

@end

@implementation ViewController

#pragma mark - Override Base Function

- (void)viewDidLoad
{
    [super viewDidLoad];
    
    [self initUI];
    [self detectFaceWithImage];
}

#pragma mark - Object Private Function

- (void)initUI
{
    UIImageView *pictureImageView = [[UIImageView alloc] initWithFrame:self.view.bounds];
    pictureImageView.contentMode = UIViewContentModeScaleAspectFit;
    pictureImageView.image = [UIImage imageNamed:@"face"];
    self.pictureImageView = pictureImageView;
    [self.view addSubview:pictureImageView];
}

- (void)detectFaceWithImage
{
    UIImage *image = [UIImage imageNamed:@"face"];
    // 圖像識別能力：可以在CIDetectorAccuracyHigh(較強的處理能力)與CIDetectorAccuracyLow(較弱的處理能力)中選擇，因為想讓準確度高一些在這里選擇CIDetectorAccuracyHigh
    NSDictionary *opts = [NSDictionary dictionaryWithObject:
                          CIDetectorAccuracyHigh forKey:CIDetectorAccuracy];
    // 將圖像轉換為CIImage
    CIImage *faceImage = [CIImage imageWithCGImage:image.CGImage];
    CIDetector *faceDetector = [CIDetector detectorOfType:CIDetectorTypeFace context:nil options:opts];
    // 識別出人臉數組
    NSArray *features = [faceDetector featuresInImage:faceImage];
    // 得到圖片的尺寸
    CGSize inputImageSize = [faceImage extent].size;
    //將image沿y軸對稱
    CGAffineTransform transform = CGAffineTransformScale(CGAffineTransformIdentity, 1, -1);
    //將圖片上移
    transform = CGAffineTransformTranslate(transform, 0, -inputImageSize.height);
    
    // 取出所有人臉
    for (CIFaceFeature *faceFeature in features){
        //獲取人臉的frame
        CGRect faceViewBounds = CGRectApplyAffineTransform(faceFeature.bounds, transform);
        CGSize viewSize = self.pictureImageView.bounds.size;
        CGFloat scale = MIN(viewSize.width / inputImageSize.width,
                            viewSize.height / inputImageSize.height);
        CGFloat offsetX = (viewSize.width - inputImageSize.width * scale) / 2;
        CGFloat offsetY = (viewSize.height - inputImageSize.height * scale) / 2;
        // 縮放
        CGAffineTransform scaleTransform = CGAffineTransformMakeScale(scale, scale);
        // 修正
        faceViewBounds = CGRectApplyAffineTransform(faceViewBounds,scaleTransform);
        faceViewBounds.origin.x += offsetX;
        faceViewBounds.origin.y += offsetY;
        
        //描繪人臉區域
        UIView* faceView = [[UIView alloc] initWithFrame:faceViewBounds];
        faceView.layer.borderWidth = 2;
        faceView.layer.borderColor = [[UIColor redColor] CGColor];
        [self.pictureImageView addSubview:faceView];
        
        // 判斷是否有左眼位置
        if(faceFeature.hasLeftEyePosition){
            NSLog(@"檢測到左眼");
        }
        // 判斷是否有右眼位置
        if(faceFeature.hasRightEyePosition){
            NSLog(@"檢測到右眼");
        }
        // 判斷是否有嘴位置
        if(faceFeature.hasMouthPosition){
            NSLog(@"檢測到嘴部");
        }
    }
}

@end

下面我們看一下輸出結果

2018-01-30 23:27:22.402634+0800 JJFaceDetector_demo1[4535:1334965] 檢測到左眼
2018-01-30 23:27:22.402767+0800 JJFaceDetector_demo1[4535:1334965] 檢測到右眼
2018-01-30 23:27:22.402811+0800 JJFaceDetector_demo1[4535:1334965] 檢測到嘴部

2018-01-30 23:27:22.402992+0800 JJFaceDetector_demo1[4535:1334965] 檢測到左眼
2018-01-30 23:27:22.403023+0800 JJFaceDetector_demo1[4535:1334965] 檢測到右眼
2018-01-30 23:27:22.403136+0800 JJFaceDetector_demo1[4535:1334965] 檢測到嘴部

2018-01-30 23:27:22.403321+0800 JJFaceDetector_demo1[4535:1334965] 檢測到左眼
2018-01-30 23:27:22.403364+0800 JJFaceDetector_demo1[4535:1334965] 檢測到右眼
2018-01-30 23:27:22.403393+0800 JJFaceDetector_demo1[4535:1334965] 檢測到嘴部

2018-01-30 23:27:22.403466+0800 JJFaceDetector_demo1[4535:1334965] 檢測到左眼
2018-01-30 23:27:22.403494+0800 JJFaceDetector_demo1[4535:1334965] 檢測到右眼
2018-01-30 23:27:22.403520+0800 JJFaceDetector_demo1[4535:1334965] 檢測到嘴部

2018-01-30 23:27:22.403590+0800 JJFaceDetector_demo1[4535:1334965] 檢測到左眼
2018-01-30 23:27:22.403617+0800 JJFaceDetector_demo1[4535:1334965] 檢測到右眼
2018-01-30 23:27:22.403641+0800 JJFaceDetector_demo1[4535:1334965] 檢測到嘴部

實現效果

接著看一下識別效果

可見，可以精確的識別出所有的人臉。

這里有幾點需要注意：

• UIView坐標系和CoreImage坐標系不一樣，UIView原點是左上角，CoreImage是左下角。所以需要使用仿射變換（AffineTransform）將Core Image坐標轉換為UIKit坐標。

//y軸對稱
CGAffineTransform transform = CGAffineTransformScale(CGAffineTransformIdentity, 1, -1);
//上移
transform = CGAffineTransformTranslate(transform, 0, -inputImageSize.height);

后記

本篇已結束，后面更精彩~~~