Question

我正在做一个视频监控项目我看不到从RGB到灰色的转换;我得到一个灰色的黑色窗口你能帮帮我解决这个问题吗？（附代码）
另外，如何获得当前帧和前一帧之间的差异？
非常感谢。伊兰

#include "stdafx.h"
#include <stdio.h>  // For printf
#include <cv.h>  
#include <cxcore.h>  
#include <highgui.h>      

int main()  
{  


    int key = 0; 



    CvCapture* capture = cvCaptureFromAVI( "macroblock.mpg" );  
    IplImage* frame = cvQueryFrame( capture );
    IplImage* gray = cvCreateImage(cvGetSize(frame),IPL_DEPTH_8U,1);
    cvCvtColor(frame, gray, CV_RGB2GRAY);

        if ( !capture ) 

    {  
        fprintf( stderr, "Cannot open AVI!\n" );  
        return 1;  
        }
          int fps = ( int )cvGetCaptureProperty( capture, CV_CAP_PROP_FPS );

           cvNamedWindow( "video", CV_WINDOW_AUTOSIZE ); 
         cvNamedWindow( "grayvideo", CV_WINDOW_AUTOSIZE ); 

        while( key != 'x' )  
    {  
        frame = cvQueryFrame( capture );




    if(key==27 )break;
     cvShowImage( "video",frame );
     cvShowImage( "grayvideo",gray );


           key = cvWaitKey( 1000 / fps );  
    }  
           cvDestroyWindow( "video" );  
    cvReleaseCapture( &capture );  

    return 0;  
}

Answer 1

您需要将每个帧从颜色转换为灰度。如果您在开始时执行一次，它不会自动转换。所以你需要添加

cvCvtColor(frame, gray, CV_BGR2GRAY);

在致电cvQueryFrame后，

进入您的while循环。

Answer 2

您的代码存在一些问题。

这是一个烂摊子，很难想象;
当您需要检查函数的返回时，您应该在调用它后立即执行。例如：cvCaptureFromAVI();
由于cvQueryFrame()可能会失败，您还需要检查它的返回值;
您忘了执行RGB - ＆gt;灰色转换：cvCvtColor(frame, gray, CV_RGB2GRAY);，然后显示灰框;
您还忘记发布 grayvideo 窗口的资源;

看起来像这样的代码是不是更容易阅读/理解？

int main()  
{      
    CvCapture* capture = cvCaptureFromAVI( "macroblock.mpg" );  
    if ( !capture ) 
    {  
        fprintf( stderr, "Cannot open AVI!\n" );  
        return 1;  
    }

    int fps = ( int )cvGetCaptureProperty( capture, CV_CAP_PROP_FPS );
    printf("FPS: %d\n", fps);

    cvNamedWindow( "video", CV_WINDOW_AUTOSIZE ); 
    cvNamedWindow( "grayvideo", CV_WINDOW_AUTOSIZE ); 

    int key = 0; 
    IplImage* gray = NULL;
    IplImage* prev_frame = NULL;

    while( key != 'x' )  
    {  
        frame = cvQueryFrame( capture );
        if (!frame) 
        {
            // print error and abort the loop
            break;
        }

        cvShowImage( "video", frame );

        if (!gray) // allocate space for the GRAY frame only once
        {
            gray = cvCreateImage(cvGetSize(frame), frame->depth,1);
        }
        cvCvtColor(frame, gray, CV_RGB2GRAY); // convert RGB frame to GRAY
        cvShowImage( "grayvideo", gray );

        if (!prev_frame) // allocate space for the GRAY frame only once
        {
            prev_frame = cvCreateImage(cvGetSize(frame), frame->depth,1);
            cvCopy( frame, prev_frame, 0 );
        }

        // perform process to compute the "difference" of the current 
        // and previous frames:
        // <add your code here>

        // then, update prev_frame now so in the next iteration it holds the previous frame
        cvCopy( frame, prev_frame, 0 );

        key = cvWaitKey( 1000 / fps );  
        if ( key==27 ) // ESC was pressed
            break;
    }  

    cvDestroyWindow( "video" );  
    cvDestroyWindow( "grayvideo" );  

    cvReleaseCapture( &capture );  

    if (gray)
        cvReleaseImage( &gray );

    if (prev_frame)
        cvReleaseImage( &prev_frame );

    return 0;  
}

Answer 3

根据您的需要使用以下opencv功能之一：

subtract(img_current,img_prev, img_diff);
absdiff(img_current, img_prev, img_diff);

OpenCV RGB为灰色

3 个答案: