OpenCV图像处理——iOS端人脸检测

前言

1.OpenCV有专门的iOS平台的包，可以真接下载导入工程，也可以用cmake把OpenCV源码编成.a文件，以静态库的形式导入工程。
2.我这里用的Xcode11,OpenCV用的是最4.20这个版本。
3.这里用到的人脸检测是OpenCV官方给的级联分类器，可以在OpenCV源码的Data目录中找到。

iOS人脸检测

1.新建一个iOS工程，把用于与C++混编的文件后缀.m改成.mm,添加一个用于做图像处理的文件，也改成.mm文件。如下：

2.把OpenCV和人脸检测的级联分类器导入工程。

3.在main.storyboard里面添加一个UIImageView,两个Button，然后关联到事件，如下：

4.处理文件里Commom.mm里面的代码：

void UIImageToMat(UIImage *ui_image, cv::Mat &cv_dst)
{
    assert(ui_image.size.width > 0 && ui_image.size.height > 0);
    assert(ui_image.CGImage != nil || ui_image.CIImage != nil);

    //开缓冲区
    NSInteger width = ui_image.size.width;
    NSInteger height = ui_image.size.height;
    cv::Mat cv_mat8uc4 = cv::Mat((int)height, (int)width, CV_8UC4);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    if (ui_image.CGImage)
    {
        CGContextRef contextRef = CGBitmapContextCreate(cv_mat8uc4.data, cv_mat8uc4.cols, cv_mat8uc4.rows, 8, cv_mat8uc4.step, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrderDefault);
        CGContextDrawImage(contextRef, CGRectMake(0, 0, width, height), ui_image.CGImage);
        CGContextRelease(contextRef);
    }
    else
    {
        static CIContext* context = nil;
        if (!context)
        {
            context = [CIContext contextWithOptions:@{ kCIContextUseSoftwareRenderer: @NO }];
        }
        CGRect bounds = CGRectMake(0, 0, width, height);
        [context render:ui_image.CIImage toBitmap:cv_mat8uc4.data rowBytes:cv_mat8uc4.step bounds:bounds format:kCIFormatRGBA8 colorSpace:colorSpace];
    }
    CGColorSpaceRelease(colorSpace);

    cv::Mat cv_mat8uc3 = cv::Mat((int)width, (int)height, CV_8UC3);
    cv::cvtColor(cv_mat8uc4, cv_mat8uc3, cv::COLOR_RGBA2BGR);

    cv_dst = cv_mat8uc3;
}

UIImage *MatToUIImage(cv::Mat &cv_src)
{
    assert(cv_src.elemSize() == 1 || cv_src.elemSize() == 3);
    cv::Mat cv_rgb;
    if (cv_src.elemSize() == 1)
    {
        cv::cvtColor(cv_src, cv_rgb, cv::COLOR_GRAY2RGB);
    } else if (cv_src.elemSize() == 3)
    {
        cv::cvtColor(cv_src, cv_rgb, cv::COLOR_BGR2RGB);
    }

    NSData *data = [NSData dataWithBytes:cv_rgb.data length:(cv_rgb.elemSize() * cv_rgb.total())];
    CGColorSpaceRef colorSpace;
    if (cv_rgb.elemSize() == 1)
    {
        colorSpace = CGColorSpaceCreateDeviceGray();
    } else
    {
        colorSpace = CGColorSpaceCreateDeviceRGB();
    }
    CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
    CGImageRef imageRef = CGImageCreate(cv_rgb.cols, cv_rgb.rows, 8, 8 * cv_rgb.elemSize(), cv_rgb.step.p[0], colorSpace, kCGImageAlphaNone|kCGBitmapByteOrderDefault, provider, NULL, false, kCGRenderingIntentDefault);
    UIImage *ui_image = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpace);

    return ui_image;
}

void faceDetection(cv::Mat &cv_src, cv::Mat &cv_dst,std::string &face_class)
{
    cv::CascadeClassifier face_classifier;
    face_classifier.load(face_class);
    if (cv_src.empty())
    {
        return;
    }
    cv_dst = cv_src.clone();

    cv::Mat cv_gray;
    //灰度化
    cv::cvtColor(cv_src, cv_gray, cv::COLOR_BGR2GRAY);
    //直方图均衡化,用于提高图像的质量
    equalizeHist(cv_gray, cv_gray);

    //存放检测到人脸的矩形
    std::vector<cv::Rect> faces;

    //开始检测
    face_classifier.detectMultiScale(cv_gray, faces, 1.2, 3, 0, cv::Size(24, 24));

    //画出检测到的矩形的位置
    for (size_t t = 0; t < faces.size(); t++)
    {
        rectangle(cv_dst, faces[static_cast<int>(t)], cv::Scalar(0, 0, 255), 2, 8, 0);
    }

}

5.交互文件ViewController.mm里面的代码：

#import "Common.h"
#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>
#import <AVKit/AVKit.h>

@interface ViewController () <UINavigationControllerDelegate, UIImagePickerControllerDelegate>

@property (strong, nonatomic) UIImagePickerController *ui_album_selected;/* 相册选择器 */
@property (strong, nonatomic) AVPlayerViewController *ui_player;/* 视频播放器 */
@property (weak, nonatomic) IBOutlet UIImageView *ui_show_view;/* 显示图片 */
@property (nonatomic, weak) UIImage *ui_selected_image;


@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    //设置显示图片可交互
    self.ui_show_view.userInteractionEnabled = YES;
    //创建AVPlayerViewController控制器
    AVPlayerViewController *playerVC = [[AVPlayerViewController alloc] init];
    playerVC.view.frame = self.ui_show_view.bounds;
    [self.ui_show_view addSubview:playerVC.view];
    self.ui_player = playerVC;
    self.ui_player.view.hidden = YES;
}
#pragma mark - UI点击
/* 点击打开本地相册 */
- (IBAction)pickImage:(id)sender
{
    //如果正在播放视频，停止播放
    if (self.ui_player.player)
    {
        [self.ui_player.player pause];
    }
    //创建图片选择控制器
    UIImagePickerController *ipc = [[UIImagePickerController alloc] init];
    //判断设备是否有图册
    if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary])
    {
        //设置拾取源类型
        ipc.sourceType =  UIImagePickerControllerSourceTypePhotoLibrary;
        //设置媒体类型，这里设置图册支持的所有媒体类型，图片和视频
        ipc.mediaTypes = [UIImagePickerController availableMediaTypesForSourceType:ipc.sourceType];
    }
    ipc.delegate = self;//设置代理
    ipc.allowsEditing = YES;//设置可编辑
    self.ui_album_selected = ipc;
    //弹出图片选择控制器
    [self presentViewController:ipc animated:YES completion:nil];
}
#pragma mark - UIImagePickerControllerDelegate代理方法
/* 选择了一个图片或者视频后调用 */
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    //获取选择文件的媒体类型
    NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];
    NSURL *videoURL = nil;
    if ([mediaType isEqualToString:@"public.image"])
    {//选择了图片
        //获取选择的图片
        self.ui_selected_image = [info objectForKey:UIImagePickerControllerOriginalImage];
        //self.ui_id = self.ui_selected_image;
        //显示图片
        self.ui_show_view.image = self.ui_selected_image;
        
        
        self.ui_show_view.contentMode = UIViewContentModeScaleAspectFit;
        NSLog(@"found an image %@",self.ui_selected_image);
        //删除视频
        self.ui_player.player = nil;
        self.ui_player.view.hidden = YES;
        
       
    }
    else if ([mediaType isEqualToString:@"public.movie"])
    {//选择了视频
        //获取临时保存视频的URL
        videoURL = [info objectForKey:UIImagePickerControllerMediaURL];
        NSLog(@"found a video %@",videoURL);
        //直接创建AVPlayer，它内部也是先创建AVPlayerItem，这个只是快捷方法
        AVPlayer *player = [AVPlayer playerWithURL:videoURL];
        self.ui_player.player = player;
        self.ui_player.view.hidden = NO;
    }
    [self dismissViewControllerAnimated:YES completion:^{
        if (videoURL) {
            //调用控制器的属性player的开始播放方法
            [self.ui_player.player play];
        }
    }];
}
/* 取消选择后调用 */
- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
{
    [self dismissViewControllerAnimated:YES completion:^
    {
        //取消选择后继续播放视频
        if (self.ui_player.player)
        {
            [self.ui_player.player play];
        }
    }];
    NSLog(@"取消选择");
}

- (IBAction)faceDetection:(id)sender
{
    NSString* const model_file_name = @"haarcascade_frontalface_default";
    NSString* const model_file_type = @"xml";
    NSString* model = [[NSBundle mainBundle] pathForResource:model_file_name ofType:model_file_type];
    std::string face_class = [model UTF8String];
    cv::Mat cv_src;
    UIImageToMat(self.ui_selected_image, cv_src);
    
    cv::Mat cv_dst;
    
    faceDetection(cv_src, cv_dst, face_class);
    
    UIImage *face_image = MatToUIImage(cv_dst);
    
    self.ui_show_view.image = face_image;
}
@end

6.连接到真机运行如下：

注：有兴趣于OpenCV学习的可以加。