将亮度/伽马控制添加到具有OpenCV图像识别功能的Objective-C定制摄像机应用程序中

Question

我在Objective-C中有一个自定义的iOS iPhone相机应用程序，该应用程序在预览层中显示摄像机流，并在视场中有特定对象时捕获帧。图像识别是通过OpenCV实现的。

该应用程序运行良好，但我想让用户能够控制视频流的亮度/伽玛，并从亮度受控的流中捕获修改后的图像。

我知道如何创建滑块控件，但是我找不到如何控制来自摄像机的视频图像的亮度/伽玛并将其显示在预览层中。摄像机通过以下AVCapture会话进行设置。

[AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) 
    {
    if(granted){ // Access has been granted ..do something
         NSLog(@"Camera Status Access Granted By User");
               //Setup Video Camera and START
         self.videoCamera = [[VideoCamera alloc] initWithParentView:self->_img];
         self.videoCamera.defaultAVCaptureDevicePosition = AVCaptureDevicePositionBack;
         self.videoCamera.defaultAVCaptureSessionPreset = AVCaptureSessionPreset640x480;
         self.videoCamera.defaultAVCaptureVideoOrientation = 
              AVCaptureVideoOrientationPortrait;
         self.videoCamera.defaultFPS = 60;
         self.videoCamera.rotateVideo = NO;
         self.videoCamera.grayscaleMode = NO;
         self.videoCamera.delegate = self;
         [self.videoCamera start];
    }

如何控制实时视频流的亮度/伽玛并将其显示在预览层中，以便随后捕获修改后的图像。

这里是预览层的设置。

- (void)layoutPreviewLayer {
if (self.parentView != nil) {

    // Center the video preview.
    self.customPreviewLayer.position = CGPointMake(0.5 * self.parentView.frame.size.width, 
    0.5 * self.parentView.frame.size.height);

    // Find the video's aspect ratio.
    CGFloat videoAspectRatio = self.imageWidth / (CGFloat)self.imageHeight;

    // Scale the video preview while maintaining its aspect ratio.
    CGFloat boundsW;
    CGFloat boundsH;
    if (self.imageHeight > self.imageWidth) {
        if (self.letterboxPreview) {
            boundsH = self.parentView.frame.size.height;
            boundsW = boundsH * videoAspectRatio;
        } else {
            boundsW = self.parentView.frame.size.width;
            boundsH = boundsW / videoAspectRatio;
        }
    } else {
        if (self.letterboxPreview) {
            boundsW = self.parentView.frame.size.width;
            boundsH = boundsW / videoAspectRatio;
        } else {
            boundsH = self.parentView.frame.size.height;
            boundsW = boundsH * videoAspectRatio;
        }
    }
    self.customPreviewLayer.bounds = CGRectMake(0.0, 0.0, boundsW, boundsH);
  }
}

任何代码，帮助和指导都将非常感谢您进行此设置。

Answer 1

我找到了几种方法来实现这一目标，并认为我会将它们发布在这里以帮助需要它的其他人。

选项1。

使用滑块使用此代码修改OpenCV Mat的像素，使其更亮或更暗。

float gammaValue = 1.5;

//EXPOSURE CONTROL USING OPENCV
- (void) gammaCorrection: (cv::Mat &)mat;
{
    float fGamma = gammaValue;
    mat.convertTo(mat, -1, fGamma, 1 ); //Control the brightness by fGamma
    NSLog(@"Gamma Value is: %f", fGamma);

}


- (IBAction)changeExposureTargetBias:(id)sender {
    UISlider *control = sender;
    NSLog(@"Target Bias %f", control.value );
    gammaValue = control.value;
}

选项2。

用滑块控制AVCaptureDevice的曝光。我的设备的曝光偏差范围是-8.0到+8.0

float exposureBIAS = 0.0;

- (void)setExposure:(float)exposureBIAS
{
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if([device isExposureModeSupported:AVCaptureExposureModeCustom])
    {
        NSError *error = nil;
        if ( [device lockForConfiguration:&error] ) {
            [device setExposureTargetBias:exposureBIAS completionHandler:nil];
            [device unlockForConfiguration];
        }
        else {
            NSLog( @"Could not lock device for configuration: %@", error );
        }
    }
}


- (IBAction)changeExposureTargetBias:(id)sender {

    UISlider *control = sender;    
    [self setExposure: control.value];

}