How to customize iOS camera in 30 minutes

Recently, the company's project used a camera. Since the system camera was not used, the camera cutouts given by the UI had to be customized. I took some time to simply study the customization of the camera.

The camera belongs to the system hardware, which requires us to manually call the iPhone's camera hardware, which is divided into the following steps:

1. First declare the following objects

 #import < AVFoundation /AVFoundation.h >  
 //Capture device, usually front camera, rear camera, microphone (audio input)
 @property (nonatomic, strong) AVCaptureDevice *device; 
 
 //AVCaptureDeviceInput represents the input device, which is initialized using AVCaptureDevice
 @property (nonatomic, strong) AVCaptureDeviceInput *input; 
 
 // Output image
 @property (nonatomic, strong) AVCaptureStillImageOutput *imageOutput; 
 
 //session: It combines the input and output together and starts the capture device (camera)
 @property (nonatomic, strong) AVCaptureSession *session; 
 
 //Image preview layer, real-time display of captured images
 @property (nonatomic, strong) AVCaptureVideoPreviewLayer *previewLayer;

2. Initialize each object

 - (void)cameraDistrict
 {
 //AVCaptureDevicePositionBack rear camera
 //AVCaptureDevicePositionFront front camera 
    self.device = [self cameraWithPosition:AVCaptureDevicePositionFront]; 
     self.input = [[AVCaptureDeviceInput alloc] initWithDevice:self.device error:nil]; 
 
     self.imageOutput = [[AVCaptureStillImageOutput alloc] init]; 
 
     self.session = [[AVCaptureSession alloc] init];
 // The size of the image obtained can be set by yourself
    //AVCaptureSessionPreset320x240
    //AVCaptureSessionPreset352x288
    //AVCaptureSessionPreset640x480
    //AVCaptureSessionPreset960x540
    //AVCaptureSessionPreset1280x720
    //AVCaptureSessionPreset1920x1080
    //AVCaptureSessionPreset3840x2160 
     self.session.sessionPreset = AVCaptureSessionPreset640x480 ;
 //Input and output device combination
    if ([self.session canAddInput:self.input]) {
        [self.session addInput:self.input];
 }
    if ([self.session canAddOutput:self.imageOutput]) {
        [self.session addOutput:self.imageOutput];
 }
 //Generate preview layer 
     self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session]; 
     self.previewLayer.frame = CGRectMake (0, 64, SCREEN_WIDTH, SCREEN_HEIGHT-64); 
     self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill ;
    [self.view.layer addSublayer:self.previewLayer];
 //Device framing starts
    [self.session startRunning];
    if ([_device lockForConfiguration:nil]) {
 //Automatic flash,
        if ([_device isFlashModeSupported:AVCaptureFlashModeAuto]) {
            [_device setFlashMode:AVCaptureFlashModeAuto];
 }
 //Automatic white balance, but it seems that I can't get it in.
        if ([_device isWhiteBalanceModeSupported:AVCaptureWhiteBalanceModeAutoWhiteBalance]) {
            [_device setWhiteBalanceMode:AVCaptureWhiteBalanceModeAutoWhiteBalance];
 }
        [_device unlockForConfiguration];
 } 
 
 }

Get the corresponding camera according to the front and rear positions:

 - (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position{
    NSArray * devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices)
        if ( device.position == position){
 return device;
 }
 return nil;
 }

3. Take a photo and get the corresponding picture:

 - (void)photoBtnDidClick
 {
    AVCaptureConnection * conntion = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
 if (!conntion) {
 NSLog(@"Photo taking failed!");
 return;
 }
    [self.imageOutput captureStillImageAsynchronouslyFromConnection:conntion completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
        if ( imageDataSampleBuffer == nil) {
 return ;
 }
        NSData * imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer]; 
         self.image = [UIImage imageWithData:imageData];
        [self.session stopRunning];
        [self.view addSubview:self.cameraImageView];
 }

4. Switch between front and rear cameras

 - (void)changeCamera{
    NSUInteger cameraCount = [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count];
 if (cameraCount > 1) {
 NSError *error;
 //Add flip animation to the camera switch
        CATransition * animation = [CATransition animation]; 
         animation.duration = .5f; 
         animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]; 
         animation.type = @"oglFlip"; 
 
        AVCaptureDevice * newCamera = nil ;
        AVCaptureDeviceInput * newInput = nil ;
 //Get another camera position
        AVCaptureDevicePosition position = [[_input device] position];
        if ( position == AVCaptureDevicePositionFront){ 
             newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack]; 
             animation.subtype = kCATransitionFromLeft ; // animation flip direction
 }
 else { 
             newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront]; 
             animation.subtype = kCATransitionFromRight ; // animation flip direction
 }
 //Generate new input 
         newInput = [AVCaptureDeviceInput deviceInputWithDevice:newCamera error:nil];
        [self.previewLayer addAnimation:animation forKey:nil];
        if (newInput != nil) {
            [self.session beginConfiguration];
            [self.session removeInput:self.input];
            if ([self.session canAddInput:newInput]) {
                [self.session addInput:newInput]; 
                 self.input = newInput ; 
 
 } else {
                [self.session addInput:self.input];
 }
            [self.session commitConfiguration]; 
 
 } else if (error) {
            NSLog(@"toggle carema failed, error = %@", error);
 }
 }
 }

5. Other camera parameter settings

 //AVCaptureFlashMode flash
 //AVCaptureFocusMode focus
 //AVCaptureExposureMode exposure
 //AVCaptureWhiteBalanceMode white balance
 //Flash and white balance can be set when generating the camera
 //Exposure is determined by the light conditions at the focus point, so write it together with the focus.
 //point is the click position
 - (void)focusAtPoint:(CGPoint)point{
    CGSize size = self .view.bounds.size;
    CGPoint focusPoint = CGPointMake ( point.y /size.height ,1-point.x/size.width );
 NSError *error;
    if ([self.device lockForConfiguration:&error]) {
 //Focus mode and focus point
        if ([self.device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {
            [self.device setFocusPointOfInterest:focusPoint];
            [self.device setFocusMode:AVCaptureFocusModeAutoFocus];
 }
 //Exposure mode and exposure point
        if ([self.device isExposureModeSupported:AVCaptureExposureModeAutoExpose]) {
            [self.device setExposurePointOfInterest:focusPoint];
            [self.device setExposureMode:AVCaptureExposureModeAutoExpose];
 } 
 
        [self.device unlockForConfiguration];
 //Set the focus animation 
         _focusView.center = point ; 
         _focusView.hidden = NO ;
        [UIView animateWithDuration:0.3 animations:^{ 
             _focusView.transform = CGAffineTransformMakeScale (1.25, 1.25);
        }completion:^(BOOL finished) {
            [UIView animateWithDuration:0.5 animations:^{ 
                 _focusView.transform = CGAffineTransformIdentity ;
            } completion:^(BOOL finished) { 
                 _focusView.hidden = YES ;
 }];
 }];
 } 
 
 }

6. Some pitfalls and solutions encountered

1) Switching between front and rear cameras

The front and back values ​​cannot be switched. I tried various ways to find the reason but couldn't find it. Later I found that I set the image size to 1080P [self.session canSetSessionPreset: AVCaptureSessionPreset1920x1080], and the front camera does not support such a large size, so the front camera cannot be switched. I verified that the front camera supports up to 720P, and can be switched freely within 720P.

Of course, you can also set different sizes according to the front and rear cameras when switching between them. I will not go into details here.

2) Focus position

CGPoint focusPoint = CGPointMake( point.y /size.height ,1-point.x/size.width );

The value range of Point after the setExposurePointOfInterest:focusPoint function is from the upper left corner of the viewfinder (0, 0) to the lower right corner of the viewfinder (1, 1). The official description is as follows:

The value of this property is a CGPoint that determines the receiver's focus point of interest, if it has one. A value of (0,0) indicates that the camera should focus on the top left corner of the image, while a value of (1,1) indicates that it should focus on the bottom right. The default value is (0.5,0.5).

I also tried to press this but the position is not right, I can only follow the above writing method. The front is the y of the click position/the height of the PreviewLayer, and the back is 1-the x of the click position/the width of the PreviewLayer

3) Focus and exposure

When I set the focus, I first set the mode setFocusMode, and then set the focus position, which will cause a very strange phenomenon. The focus position is the position you clicked last time. So you must set the position first, and then set the focus mode.

Exposure same as above

7. Final words

Attached demo: https://github.com/nanshanyi/photographDemo

These are the basic ones that are commonly used. This is not perfect. If there is anything wrong, you are welcome to criticize and correct me so that we can learn together.