c++ - 使用 OpenCV 2.4.3 的双线性插值的 VideoCapture 旋转

Question

我正在使用双线性插值实现视频捕捉旋转，就像 OpenCV 库中的 warpAffine() 一样。但到目前为止我遇到了一些问题:

1.我在轮换期间得到了一些伪像。以下是边框、90 度旋转和 360 度伪像的示例

https://www.dropbox.com/sh/oe51ty0cy695i3o/hcAzwmAk6z

2.我无法使用

更改捕获的分辨率

capture.set(CV_CAP_PROP_FRAME_WIDTH, 1280 )
capture.set(CV_CAP_PROP_FRAME_HEIGHT, 720 )

两者都返回假值。

我使用 LifeCam Cinema。

这是我的代码:

#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>

#include <cmath>
#include <ctime>

#include <iostream>
#include <cstdlib>

using namespace cv;
using namespace std;

const double M_PI = 3.14159265359;

void print_help( const char* prg );
Mat rotate( Mat& in, int angle , Point2f rotationCenter );

inline uchar int2uchar( int color  ) {
    return (uchar)( color < 0 ? 0 : color > 255 ? 255 : color );
}

void print_help( const char* prg ) {
    cout << "Report:" << endl;
    cout << "Application : " << prg << endl;
    cout << "Can't access capture device" << endl;
}

// rotation with bilinear interpolation
Mat rotate( Mat& in, int angle , Point2f rotationCenter ) {

    // Note : added Scalar(0) for unused pixels to be black
    Mat out( in.size(), in.type(), Scalar(0) );

    float in_radians    = (float)( angle * M_PI / 180 );
    float sinAngle      = (float)( sin( in_radians ) );
    float cosAngle      = (float)( cos( in_radians ) );

    for ( int col(0); col < in.cols; ++col ) {
        for ( int row(0); row < in.rows; ++row ) {

            // already around rotationCenter
            // x' = x * cos(angle) - y * sin(angle)
            float temp_columns( ( col    - rotationCenter.x ) * (cosAngle) -
                                ( row    - rotationCenter.y ) * (sinAngle) +
                                rotationCenter.x );
            // y' = x * sin(angle) + y * cos(angle)
            float temp_rows   ( ( col    - rotationCenter.x ) * (sinAngle) +
                                ( row    - rotationCenter.y ) * (cosAngle) +
                                rotationCenter.y );

            float max_col( ceil (temp_columns) );
            float min_col( floor(temp_columns) );
            float max_row( ceil (temp_rows)  );
            float min_row( floor(temp_rows)  );

            // clip all irrelevant parts
            if ( max_col >= in.cols || max_row >= in.rows ||
                        min_col < 0 || min_row < 0 ) {
                // don't draw
                continue;
            }

            float deltaCol( temp_columns - min_col );
            float deltaRow( temp_rows     - min_row );

            // left top, right top, left bottom and right bottom
            Vec3b q12( in.at < Vec3b >( (int)min_row, (int)min_col ) );
            Vec3b q22( in.at < Vec3b >( (int)min_row, (int)max_col ) );
            Vec3b q11( in.at < Vec3b >( (int)max_row, (int)min_col ) );
            Vec3b q21( in.at < Vec3b >( (int)max_row, (int)max_col ) );

            // R1 - linear interpolation of bottom neighborhoods
            double blueR1   ( ( 1 - deltaCol ) * q11[0] + deltaCol * q21[0] );
            double greenR1  ( ( 1 - deltaCol ) * q11[1] + deltaCol * q21[1] );
            double redR1    ( ( 1 - deltaCol ) * q11[2] + deltaCol * q21[2] );

            // R2 - linear interpolation of top neighborhoods
            double blueR2   ( ( 1 - deltaCol ) * q12[0] + deltaCol * q22[0] );
            double greenR2  ( ( 1 - deltaCol ) * q12[1] + deltaCol * q22[1] );
            double redR2    ( ( 1 - deltaCol ) * q12[2] + deltaCol * q22[2] );

            // P - linear interpolation of R1 and R2
            int blue ( (int)ceil( ( 1 - deltaRow ) * blueR2 + deltaRow * blueR1   ) );
            int green( (int)ceil( ( 1 - deltaRow ) * greenR2 + deltaRow * greenR1 ) );
            int red  ( (int)ceil( ( 1 - deltaRow ) * redR2  + deltaRow * redR1    ) );

            // Vec3b stands for 3-channel value, each channel is a byte
            out.at < Vec3b >( row, col )[ 0 ] = int2uchar(blue);
            out.at < Vec3b >( row, col )[ 1 ] = int2uchar(green);
            out.at < Vec3b >( row, col )[ 2 ] = int2uchar(red);
        }
    }

    return out;
}

int main( int ac, char ** av ) {
   if ( ac < 2 ) {
      print_help( av[ 0 ] );
      return -1;
   }

   // In degrees
   int step = 1, angle = 90;

   VideoCapture capture;

   // doesn't work properly
   if ( capture.set(CV_CAP_PROP_FRAME_WIDTH, 1280 ) &&
        capture.set(CV_CAP_PROP_FRAME_HEIGHT, 720 ) ) {
       cout << "Resolution : "
            << capture.get(CV_CAP_PROP_FRAME_WIDTH )
            << " x "
            << capture.get(CV_CAP_PROP_FRAME_HEIGHT )
            << endl;
   } else {
       cout << "There's some problem with VideoCapture::set()" << endl;
   }

   capture.open( atoi( av[ 1 ] ) );

   while ( !capture.isOpened( ) ) {
       print_help( av[ 0 ] );
       cout << "Capture device " << atoi( av[ 1 ] ) << " failed to open!" << endl;
       cout << "Connect capture device to PC\a" << endl;
       system("pause");
       cout << endl;
       capture.open( atoi( av[ 1 ] ) );
   }

   cout << "Device " << atoi( av[ 1 ] ) << " is connected" << endl;

   string original("Original");
   string withInterpolation("With Bilinear Interpolation");

   namedWindow( original, CV_WINDOW_AUTOSIZE );
   namedWindow( withInterpolation, CV_WINDOW_AUTOSIZE);

   Mat frame;

   for ( ;; ) {
      capture >> frame;
      if ( frame.empty( ) )
         break;

      createTrackbar("Rotate", withInterpolation, &angle, 360, 0);

      imshow( original, frame );

      char key = ( char ) waitKey( 2 );
      switch ( key ) {
      case '+':
         angle += step;
         break;
      case '-':
         angle -= step;
         break;
      case 27:
      case 'q':
         return 0;
         break;
      }

      Mat result;

      Point2f rotationCenter( (float)( frame.cols / 2.0 ),
                              (float)( frame.rows / 2.0 ) );

      result = rotate( frame, angle, rotationCenter );

      // Note : mirror effect
      // 1 says, that given frame will be flipped horizontally
      flip(result,result, 1);

      imshow( withInterpolation, result );

      // test to compare my bilinear interpolation and of OpenCV
      Mat temp;
      warpAffine( frame, temp,
                  getRotationMatrix2D( rotationCenter, angle, (double)(1.0) ),
                  frame.size(), 1, 0 );
      string openCVInterpolation("OpenCV Bilinear Interpolation");
      namedWindow( openCVInterpolation, CV_WINDOW_AUTOSIZE );
      createTrackbar("Rotate", openCVInterpolation, &angle, 360, 0);
      flip(temp,temp, 1);
      imshow( openCVInterpolation, temp );
   }

   return 0;
}

Answer 1

解决您的第二个问题 - 使用 OpenCV 设置 Lifecam 分辨率

我发现 Lifecam 仪表板可能会干扰 OpenCV Videocapture 调用。如果您使用控制面板中的程序和功能卸载 Lifecam，调用

capture.set(CV_CAP_PROP_FRAME_WIDTH, 1280)
capture.set(CV_CAP_PROP_FRAME_HEIGHT, 720)

将正常工作。