Kristou Says » OpenCV

Color interpolation in OpenCV

Kristou Mehrez — Wed, 23 Dec 2009 04:23:07 +0000

I could not find in Internet a function which can return a RGB color value between two colors So I had to do it myself. I hope it will be useful for someone.

CvScalar interpolate(CvScalar c1, CvScalar c2, double value){ if( value <= 0.0 ){ return c1; } if( value >= 1.0 ){ return c2; } int red = cvRound((1.0 - value) * c1.val[2] + value * c2.val[2]); int green = cvRound((1.0 - value) * c1.val[1] + value * c2.val[1]); int blue = cvRound((1.0 - value) * c1.val[0] + value * c2.val[0]); return CV_RGB(red, green, blue); }

Edge orientation

Kristou Mehrez — Sat, 05 Dec 2009 10:31:26 +0000

This is a sample code for getting the edges orientation in an image.

CvMat *filter_x=cvCreateMat(1,3,CV_32FC1); filter_x->data.fl[0]=-1; filter_x->data.fl[1]=0; filter_x->data.fl[2]=1; CvMat *filter_y=cvCreateMat(3,1,CV_32FC1); filter_y->data.fl[0]=-1; filter_y->data.fl[1]=0; filter_y->data.fl[2]=1; IplImage *img_src=cvLoadImage("name",0); IplImage *img_diff_x=cvCreateImage(cvGetSize(img_src),IPL_DEPTH_32F,1); IplImage *img_diff_y=cvCreateImage(cvGetSize(img_src),IPL_DEPTH_32F,1); IplImage *img_32f=cvCreateImage(cvGetSize(img_src),IPL_DEPTH_32F,1); cvConvert(img_src,img_32f); cvFilter2D(img_32f,filter_x,img_diff_x); cvFilter2D(img_32f,filter_y,img_diff_y); IplImage *magnitude=cvCreateImage(cvGetSize(img_src),IPL_DEPTH_32F,1); IplImage *orientation=cvCreateImage(cvGetSize(img_src),IPL_DEPTH_32F,1); cvCartToPolar(img_diff_x, img_diff_y, magnitude, orientation, 1);

Convert Polar image into Cartesian

Kristou Mehrez — Wed, 25 Nov 2009 16:27:54 +0000

This a simple implementation of Polar to Cartesian transformation applied to the image case. It is useful to unroll an omni image to convert it to panoramic image.

imgPol = cvCreateImage(cvSize(2*CV_PI*RadiusMax,RadiusMax-RadiusMin),IPL_DEPTH_8U,1);
cvSet(imgPol,CV_WHITE,NULL);
int x0,y0;
double Radius;
double Angle;
for(int x=1; x < imgPol->width; x++)
{
	for(int y=1; y < imgPol->height; y++)
	{
		Radius = RadiusMin + y;
		Angle = 2 * CV_PI * x / imgPol->width;
		x0 = cvRound(CenterX + Radius * cos(Angle));
		y0 = cvRound(CenterY + Radius * sin(Angle));

		cvSet2D(imgPol, y, x, cvGet2D(imgBase,y0,x0));
	}
}

cvSaveImage("imgPol.bmp",imgPol);

Closing gaps in image

Kristou Mehrez — Wed, 18 Nov 2009 14:42:45 +0000

This an example on how to use morphological operator in OpenCV to close gaps.

int main(int argc, char* argv[])

{

IplImage *image;

IplImage *dilated_image;

IplImage *eroded_image;

image = cvLoadImage ("triangle.jpg");
dilated_image = cvCloneImage (image);

eroded_image = cvCloneImage (image);
cvNamedWindow ("Original", 1);

cvNamedWindow ("Dilated", 1);

cvNamedWindow ("Eroded", 1);
cvShowImage ("Original", image);
cvDilate (image, dilated_image, 0, 7);

cvShowImage ("Dilated", dilated_image);
cvErode (dilated_image, eroded_image, 0, 6);

cvShowImage ("Eroded", eroded_image);
cvWaitKey ();
cvReleaseImage (&image);

cvDestroyWindow ("Original");

cvReleaseImage (&dilated_image);

cvDestroyWindow ("Dilated");

cvReleaseImage (&eroded_image);

cvDestroyWindow ("Eroded");
return 0;

}

Circle detection

Kristou Mehrez — Mon, 16 Nov 2009 12:54:06 +0000

This a source code for sircle detection.

void findCircles( IplImage* img, CvMemStorage* storage ){
CvSeq* circles;
IplImage* cpy = cvCreateImage(cvGetSize(img),8,1);
int i;
float* circ;
cvCvtColor(img,cpy,CV_RGB2GRAY);
circles =
cvHoughCircles(cpy,storage,CV_HOUGH_GRADIENT,2,cpy->height/4,200,100);
for(i=0;i < circles->total;i++){
CvSeq
circ=(float*)cvGetSeqElem(circles,i);

cvCircle(img,cvPoint(cvRound(circ[0]),cvRound(circ[1])),cvRound(circ[2]),CV_RGB(255,255,255),1,8,0);
}
cvReleaseImage(&cpy);

}