Andrew Seaford

To separate a multi channel image into the three component RGB channels, we can use the cvSplit function. The example below opens a RGB image and then using the cvSplit function creates three output images.

#include "stdafx.h"
#include "cv.h"
#include "highgui.h"

int _tmain(int argc, _TCHAR* argv[])
{
	// open and display input image  
    IplImage* input = cvLoadImage("test.jpg");  
    cvNamedWindow("Input", CV_WINDOW_AUTOSIZE);  
    cvShowImage("Input", input); 

	// create the output images
	IplImage* output_r = cvCreateImage(cvSize(input->width, input->height), input->depth, 1);
	IplImage* output_g = cvCreateImage(cvSize(input->width, input->height), input->depth, 1);
	IplImage* output_b = cvCreateImage(cvSize(input->width, input->height), input->depth, 1);

	// split the image
	cvSplit(input, output_r, output_g, output_b,NULL);
	
	// display image
	cvNamedWindow("Output R", CV_WINDOW_AUTOSIZE);
	cvShowImage("Output R", output_r);

	cvNamedWindow("Output G", CV_WINDOW_AUTOSIZE);
	cvShowImage("Output G", output_g);

	cvNamedWindow("Output B", CV_WINDOW_AUTOSIZE);
	cvShowImage("Output B", output_b);

	// wait for user
	cvWaitKey(0);

	// garbage collection	
	cvReleaseImage(&input);
	cvDestroyWindow("Input");
	cvReleaseImage(&output_r);
	cvDestroyWindow("Output R");
	cvReleaseImage(&output_g);
	cvDestroyWindow("Output G");
	cvReleaseImage(&output_b);
	cvDestroyWindow("Output B");
	return 0;
}

Input Image

Blue Channel

Green Channel

Red Channel

Here is the Hello World example code for OpenCV. This simple example creates a image called output, then the text “Hello World” is added to the image.

#include "stdafx.h"
#include "cv.h"
#include "highgui.h"

int _tmain(int argc, _TCHAR* argv[])
{
	// create image
	IplImage* output = cvCreateImage(cvSize(400, 200), 8, 3);
	
	// create font and add text to the image
	CvFont font;
    cvInitFont(&font, CV_FONT_HERSHEY_SIMPLEX, 1,1,0,1,8);
	cvPutText(output, "Hello World", cvPoint(100,100), &font, cvScalar(255,255,0));
	
	// display image
	cvNamedWindow("Output", CV_WINDOW_AUTOSIZE);
	cvShowImage("Output", output);

	// wait for user
	cvWaitKey(0);

	// garbage collection	
	cvReleaseImage(&output);
	cvDestroyWindow("Output");
	
	return 0;
}

Hello World output image