samples/cpp/warpPerspective_demo.cpp


An example program shows using cv::findHomography and cv::warpPerspective for image warping

#include <iostream>
using namespace std ;
using namespace cv ;
static void help( char ** argv)
{
// print a welcome message, and the OpenCV version
cout << "\nThis is a demo program shows how perspective transformation applied on an image, \n"
"Using OpenCV version " << CV_VERSION << endl;
cout << "\nUsage:\n" << argv[0] << " [image_name -- Default right.jpg]\n" << endl;
cout << "\nHot keys: \n"
"\tESC, q - quit the program\n"
"\tr - change order of points to rotate transformation\n"
"\tc - delete selected points\n"
"\ti - change order of points to inverse transformation \n"
"\nUse your mouse to select a point and move it to see transformation changes" << endl;
}
static void onMouse( int event, int x, int y, int , void *);
Mat warping( Mat image, Size warped_image_size, vector< Point2f> srcPoints, vector< Point2f> dstPoints);
字符串 windowTitle = "Perspective Transformation Demo" ;
字符串 labels[4] = { "TL" , "TR" , "BR" , "BL" };
vector< Point2f> roi_corners;
vector< Point2f> dst_corners(4);
int roiIndex = 0;
bool dragging;
int selected_corner_index = 0;
bool validation_needed = true ;
int main( int argc, char ** argv)
{
help(argv);
CommandLineParser parser(argc, argv, "{@input| right.jpg |}" );
string filename = samples::findFile (parser. get < string >( "@input" ));
Mat original_image = imread ( filename );
Mat image;
float original_image_cols = (float)original_image. cols ;
float original_image_rows = ( float )original_image. rows ;
roi_corners.push_back( Point2f ( ( float )(original_image_cols / 1.70), ( float )(original_image_rows / 4.20) ));
roi_corners.push_back( Point2f ( ( float )(original_image. cols / 1.15), ( float )(original_image. rows / 3.32) ));
roi_corners.push_back( Point2f ( ( float )(original_image. cols / 1.33), ( float )(original_image. rows / 1.10) ));
roi_corners.push_back( Point2f ( ( float )(original_image. cols / 1.93), ( float )(original_image. rows / 1.36) ));
namedWindow ( "Warped Image" , WINDOW_AUTOSIZE );
moveWindow ( "Warped Image" , 20, 20);
moveWindow (windowTitle, 330, 20);
setMouseCallback (windowTitle, onMouse, 0);
bool endProgram = false ;
while (!endProgram)
{
if ( validation_needed & (roi_corners.size() < 4) )
{
validation_needed = false ;
image = original_image. clone ();
for ( size_t i = 0; i < roi_corners.size(); ++i)
{
circle ( image, roi_corners[i], 5, Scalar (0, 255, 0), 3 );
if ( i > 0 )
{
line (image, roi_corners[i-1], roi_corners[(i)], Scalar (0, 0, 255), 2);
circle (image, roi_corners[i], 5, Scalar (0, 255, 0), 3);
putText (image, labels[i].c_str(), roi_corners[i], FONT_HERSHEY_SIMPLEX , 0.8, Scalar (255, 0, 0), 2);
}
}
imshow ( windowTitle, image );
}
if ( validation_needed & ( roi_corners.size() == 4 ))
{
image = original_image. clone ();
for ( int i = 0; i < 4; ++i )
{
line (image, roi_corners[i], roi_corners[(i + 1) % 4], Scalar (0, 0, 255), 2);
circle (image, roi_corners[i], 5, Scalar (0, 255, 0), 3);
putText (image, labels[i].c_str(), roi_corners[i], FONT_HERSHEY_SIMPLEX , 0.8, Scalar (255, 0, 0), 2);
}
imshow ( windowTitle, image );
dst_corners[0].x = 0;
dst_corners[0].y = 0;
dst_corners[1].x = (float) std::max ( norm (roi_corners[0] - roi_corners[1]), norm (roi_corners[2] - roi_corners[3]));
dst_corners[1].y = 0;
dst_corners[2].x = (float) std::max ( norm (roi_corners[0] - roi_corners[1]), norm (roi_corners[2] - roi_corners[3]));
dst_corners[2].y = (float) std::max ( norm (roi_corners[1] - roi_corners[2]), norm (roi_corners[3] - roi_corners[0]));
dst_corners[3].x = 0;
dst_corners[3].y = (float) std::max ( norm (roi_corners[1] - roi_corners[2]), norm (roi_corners[3] - roi_corners[0]));
Size warped_image_size = Size ( cvRound (dst_corners[2].x), cvRound (dst_corners[2].y));
Mat H = findHomography (roi_corners, dst_corners); //get homography
Mat warped_image;
warpPerspective (original_image, warped_image, H, warped_image_size); // do perspective transformation
imshow ( "Warped Image" , warped_image);
}
char c = (char) waitKey ( 10 );
if ((c == 'q' ) | (c == 'Q' ) | (c == 27))
{
endProgram = true ;
}
if ((c == 'c' ) | (c == 'C' ))
{
roi_corners.clear();
}
if ((c == 'r' ) | (c == 'R' ))
{
roi_corners.push_back(roi_corners[0]);
roi_corners.erase(roi_corners.begin());
}
if ((c == 'i' ) | (c == 'I' ))
{
swap (roi_corners[0], roi_corners[1]);
swap (roi_corners[2], roi_corners[3]);
}
}
return 0;
}
static void onMouse( int event, int x, int y, int , void *)
{
// Action when left button is pressed
if (roi_corners.size() == 4)
{
for ( int i = 0; i < 4; ++i)
{
if ((event == EVENT_LBUTTONDOWN ) & (( abs (roi_corners[i].x - x) < 10)) & ( abs (roi_corners[i].y - y) < 10))
{
selected_corner_index = i;
dragging = true ;
}
}
}
else if ( event == EVENT_LBUTTONDOWN )
{
roi_corners.push_back( Point2f ( ( float ) x, ( float ) y ) );
validation_needed = true ;
}
// Action when left button is released
if (event == EVENT_LBUTTONUP )
{
dragging = false ;
}
// Action when left button is pressed and mouse has moved over the window
if ((event == EVENT_MOUSEMOVE ) && dragging)
{
roi_corners[selected_corner_index].x = (float) x;
roi_corners[selected_corner_index].y = (float) y;
validation_needed = true ;
}
}