OpenCV鼠标画图例程，鼠标绘制矩形

// An example program in which the
// user can draw boxes on the screen.
//
/* License:
Oct. 3, 2008
Right to use this code in any way you want without warrenty, support or any guarentee of it working.

BOOK: It would be nice if you cited it:
Learning OpenCV: Computer Vision with the OpenCV Library
by Gary Bradski and Adrian Kaehler
Published by O'Reilly Media, October 3, 2008

AVAILABLE AT: http://www.amazon.com/Learning-OpenCV-Computer-Vision-Library/dp/0596516134 Or: http://oreilly.com/catalog/9780596516130/ ISBN-10: 0596516134 or: ISBN-13: 978-0596516130

OTHER OPENCV SITES:
* The source code is on sourceforge at: http://sourceforge.net/projects/opencvlibrary/ * The OpenCV wiki page (As of Oct 1, 2008 this is down for changing over servers, but should come back): http://opencvlibrary.sourceforge.net/ * An active user group is at: http://tech.groups.yahoo.com/group/OpenCV/ * The minutes of weekly OpenCV development meetings are at: http://pr.willowgarage.com/wiki/OpenCV */
#include <cv.h>
#include <highgui.h>
#pragma comment(lib,"opencv_core2410d.lib")
#pragma comment(lib,"opencv_highgui2410d.lib")

// Define our callback which we will install for
// mouse events.
//
void my_mouse_callback( int event, int x, int y, int flags, void* param );

CvRect box;
bool drawing_box = false;

// A litte subroutine to draw a box onto an image
//
void draw_box( IplImage* img, CvRect rect )
{
cvRectangle
(
img,
cvPoint(box.x,box.y),
cvPoint(box.x+box.width,box.y+box.height),
cvScalar(0xff,0x00,0x00)    /* red */
);
}

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

box = cvRect(-1,-1,0,0);

IplImage* image = cvCreateImage(
cvSize(200,200),
IPL_DEPTH_8U,
3
);
cvZero( image );
IplImage* temp = cvCloneImage( image );

cvNamedWindow( "Box Example" );

// Here is the crucial moment that we actually install
// the callback.  Note that we set the value ‘param’ to
// be the image we are working with so that the callback
// will have the image to edit.
//
cvSetMouseCallback(
"Box Example",
my_mouse_callback,
(void*) image
);

// The main program loop.  Here we copy the working image
// to the ‘temp’ image, and if the user is drawing, then
// put the currently contemplated box onto that temp image.
// display the temp image, and wait 15ms for a keystroke,
// then repeat…
//
while( 1 ) {

cvCopyImage( image, temp );
if( drawing_box ) draw_box( temp, box );
cvShowImage( "Box Example", temp );

if( cvWaitKey( 15 )==27 ) break;
}

// Be tidy
//
cvReleaseImage( &image );
cvReleaseImage( &temp );
cvDestroyWindow( "Box Example" );
}

// This is our mouse callback.  If the user
// presses the left button, we start a box.
// when the user releases that button, then we
// add the box to the current image.  When the
// mouse is dragged (with the button down) we
// resize the box.
//
void my_mouse_callback(
int event, int x, int y, int flags, void* param )
{

IplImage* image = (IplImage*) param;

switch( event ) {
case CV_EVENT_MOUSEMOVE: {
if( drawing_box ) {
box.width  = x-box.x;
box.height = y-box.y;
}
}
break;
case CV_EVENT_LBUTTONDOWN: {
drawing_box = true;
box = cvRect( x, y, 0, 0 );
}
break;
case CV_EVENT_LBUTTONUP: {
drawing_box = false;
if( box.width<0  ) {
box.x+=box.width;
box.width *=-1;
}
if( box.height<0 ) {
box.y+=box.height;
box.height*=-1;
}
draw_box( image, box );
}
break;
}
}