OpenCV

ตัวอย่างนี้แสดงถึงวิธีการใช้คำสั่งของ OpenCV เพื่อทำ edge detection โดยใช้วิธีของ Canny

#include 
using namespace std;

#include 
#include 
#include 

#define CAMERA_ID 0
#define ORG_IMAGE_DISPLAY  "original image"
#define PROCESSED_IMAGE_DISPLAY "processed image"

#define STRONG_EDGE_TH 100
#define WEAK_EDGE_TH 10

int main( int argc, char **argv )
{
    // create camera capture object.
    CvCapture *pCapture = NULL;
    pCapture = cvCreateCameraCapture( CAMERA_ID );
    if ( pCapture == NULL )
        {
            cout << "ERROR: Failed to open camera" << endl;
            return EXIT_FAILURE;
        }

    // create windows for displaying the captured image
    // and the captured image.
    cvNamedWindow( ORG_IMAGE_DISPLAY );
    cvNamedWindow( PROCESSED_IMAGE_DISPLAY );

    // capture, process, and display
    // until user hit any key of the keyboard
    IplImage *pOrgImage = NULL;
    IplImage *pProcessedImage = NULL;
    do
    {
        // release old image
        // before creating a new one
        if ( pProcessedImage != NULL )
            {
             cvReleaseImage( &pProcessedImage );
             pProcessedImage = NULL;
            }

        // capture new image
        pOrgImage = cvQueryFrame( pCapture );

        // create image which has the same width, height, depth, and number of channels
        // as the original image for put the result of processing.
        pProcessedImage = cvCreateImage( cvSize( pOrgImage->width, pOrgImage->height ),
                    pOrgImage->depth, 1 );

        // do canny edge dectection
        cvCvtColor( pOrgImage, pProcessedImage, CV_BGR2GRAY );
        cvCanny( pProcessedImage, pProcessedImage, STRONG_EDGE_TH, WEAK_EDGE_TH );

        // display images
        cvShowImage( ORG_IMAGE_DISPLAY, pOrgImage );
        cvShowImage( PROCESSED_IMAGE_DISPLAY, pProcessedImage );
    } while ( cvWaitKey( 1 ) == -1 );

    // release old image
    if ( pProcessedImage != NULL )
        {
            cvReleaseImage( &pProcessedImage );
            pProcessedImage = NULL;
        }

    // before exiting the program,
    // destroy the display windows and
    // release the cameara capture object.
    cvDestroyWindow( ORG_IMAGE_DISPLAY );
    cvDestroyWindow( PROCESSED_IMAGE_DISPLAY );
    cvReleaseCapture( &pCapture );
    return 0;
}

ตัวอย่างนี้แสดงวิธีการเบื้องต้น เพื่อแสดงวิธีการเข้าถึงข้อมูลแต่ละ pixel ของภาพ เพื่อทำการตัดสีตามค่าช่วงสีที่กำหนดไว้

#include 
using namespace std;

#include 
#include 
#include 

#define CAMERA_ID 0
#define ORG_IMAGE_DISPLAY  "original image"
#define PROCESSED_IMAGE_DISPLAY "processed image"

// interested color value
#define RED_MIN  0
#define RED_MAX 255
#define GREEN_MIN 0
#define GREEN_MAX 100
#define BLUE_MIN 0
#define BLUE_MAX 100

// channel indices
#define BLUE_CH  0
#define GREEN_CH 1
#define RED_CH  2

int main( int argc, char **argv )
{
    // create camera capture object.
    CvCapture *pCapture = NULL;
    pCapture = cvCreateCameraCapture( CAMERA_ID );
    if ( pCapture == NULL )
        {
            cout << "ERROR: Failed to open camera" << endl;
            return EXIT_FAILURE;
        }

    // create windows for displaying the captured image
    // and the captured image.
    cvNamedWindow( ORG_IMAGE_DISPLAY );
    cvNamedWindow( PROCESSED_IMAGE_DISPLAY );

    // capture, process, and display
    // until user hit any key of the keyboard
    IplImage *pOrgImage = NULL;
    IplImage *pProcessedImage = NULL;
    do
    {
        // release old image
        // before creating a new one
        if ( pProcessedImage != NULL )
            {
                cvReleaseImage( &pProcessedImage );
                pProcessedImage = NULL;
            }

        // capture new image
        pOrgImage = cvQueryFrame( pCapture );

        // create image which has the same width, height, depth, and number of channels
        // as the original image for put the result of processing.
        // Then fill the created image with 0 value ( black image ).
        pProcessedImage = cvCreateImage( cvSize( pOrgImage->width, pOrgImage->height ),
                    pOrgImage->depth, pOrgImage->nChannels );
        cvSetZero( pProcessedImage );

        // threshold the image by accessing all pixels of the image
        for ( int y = 0; y < pOrgImage->height; y++ )
        {
            for ( int x = 0; x < pOrgImage->width; x++ )
            {
                int offset_x = x*pOrgImage->nChannels;
                int offset_y = y*pOrgImage->widthStep;
                unsigned char *pPixel = (unsigned char*)pOrgImage->imageData + (offset_x + offset_y);
                unsigned char *pDstPixel = (unsigned char*)pProcessedImage->imageData + (offset_x + offset_y);

                if ( ( pPixel[BLUE_CH] >= BLUE_MIN && pPixel[BLUE_CH] <= BLUE_MAX )
                        && ( pPixel[GREEN_CH] >= GREEN_MIN && pPixel[GREEN_CH] <= GREEN_MAX )
                        && ( pPixel[RED_CH] >= RED_MIN && pPixel[RED_CH] <= RED_MAX ) )
                    {
                        pDstPixel[RED_CH] = pDstPixel[GREEN_CH] = pDstPixel[BLUE_CH] = 255;
                    }
            }
        }

        // display images
        cvShowImage( ORG_IMAGE_DISPLAY, pOrgImage );
        cvShowImage( PROCESSED_IMAGE_DISPLAY, pProcessedImage );
    } while ( cvWaitKey( 1 ) == -1 );

    // release old image
    if ( pProcessedImage != NULL )
        {
            cvReleaseImage( &pProcessedImage );
            pProcessedImage = NULL;
        }

    // before exiting the program,
    // destroy the display windows and
    // release the cameara capture object.
    cvDestroyWindow( ORG_IMAGE_DISPLAY );
    cvDestroyWindow( PROCESSED_IMAGE_DISPLAY );
    cvReleaseCapture( &pCapture );
    return 0;
}

การติดต่อกับกล้องโดย OpenCV นั้นจะใช้ชุดคำสั่งจาก highgui ซึ่งมีตัวอย่างดังนี้

#include 
using namespace std;
#include 
#include 
#define CAMERA_ID 0
#define DISPLAY_WINDOW_NAME "captured image"
int main( int argc, char **argv )
{
// create camera capture object.
CvCapture *pCapture = NULL;
pCapture = cvCreateCameraCapture( CAMERA_ID );
if ( pCapture == NULL )
{
cout << "ERROR: Failed to open camera" << endl;
return EXIT_FAILURE;
}
// create window for displaying captured image.
cvNamedWindow( DISPLAY_WINDOW_NAME );
// capture and display
// until user hit any key of the keyboard
IplImage *pImage = NULL;
do
{
pImage = cvQueryFrame( pCapture );
cvShowImage( DISPLAY_WINDOW_NAME, pImage );
} while ( cvWaitKey( 1 ) == -1 );
// before exiting the program,
// destroy the display window and
// release the cameara capture object.
cvDestroyWindow( DISPLAY_WINDOW_NAME );
cvReleaseCapture( &pCapture );
return 0;
}

ข้อดีของ Opencv

Q จะเริ่มเล่น Image Processing ใช้ opencv ดีไหมครับ


A คือคำว่า “เล่น image Processing” นี่หมายความกว้างแค่ไหนเหรอครับ

1. MinGW: เป็นชุดคำสั่งรวมพวกไลบรารี่ของภาษา Programming ซึ่งในที่นี้โปรแกรมที่จะติดตั้งก็คือ C/C++ compiler
2. Eclipse CDT: ดั้งเดิมเป็น IDE สำหรับภาษา Java แต่ตัวนี้ได้ติดตั้งโปรแกรมเสริมให้รองรับการพัฒนาภาษา C/C++
3. OpenCV for Windows: และแน่นอนที่ขาดไม่ได้ นั่นก็คือ OpenCV ซึ่งเป็นชุดคำสั่งรวมพวกไลบรารี่ของการพัฒนาโปรแกรมทาง Computer Vision หรือ Image Processing