Stitching 3 images - c++

Question

the function stitches two images...that works fine...
function:
for( int i = 1; i<(4); i++ )
{
test=Bildpaar(test,image1[2+z]);
z=z+1;
}
imwrite("../superrechts.jpg",test);
but the second iteration fails because there is a Black part of the pano image and I can only see the third image...
my function
Mat Bildpaar(Mat Bild1,Mat Bild2)
{
Mat img_keypoints_1;
std::vector<KeyPoint> keypoints_1,keypoints_2;//anzahl der keypoint vektoren
int minHessian = 50;
FastFeatureDetector detector( minHessian);
detector.detect( Bild1, keypoints_1 );
detector.detect( Bild2, keypoints_2 );
//-- Draw keypoints
drawKeypoints( Bild1, keypoints_1, img_keypoints_1, Scalar::all(-1), DrawMatchesFlags::DEFAULT );
//%%%%%%%%%%%%%%%%%%%%%%%%&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
//Discriptor
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
SiftDescriptorExtractor extractor; //Zeit
Mat descriptors_1,descriptors_2;
extractor.compute( Bild1, keypoints_1, descriptors_1 );
extractor.compute( Bild2, keypoints_2, descriptors_2 );
// waitKey(0);
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//Matcher
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//-- Step 3: Matching descriptor vectors using FLANN matcher
std::vector< DMatch > matches;
FlannBasedMatcher matcher;
matcher.match( descriptors_1, descriptors_2, matches );
double max_dist = 0; double min_dist = 100;
Mat img_matches;
drawMatches(Bild1, keypoints_1, Bild2, keypoints_2, matches, img_matches);
//namedWindow( filename, CV_WINDOW_NORMAL );// Create a window for display.
//imshow(filename, img_matches[i]);
std::vector< DMatch > good_matches;
for( int i = 0; i < descriptors_1.rows; i++ )
{ double dist = matches[i].distance;
if( dist < min_dist ) min_dist = dist;
if( dist > max_dist ) max_dist = dist;
}
for( int i = 0; i < descriptors_1.rows; i++ )
{ if( matches[i].distance < 2*min_dist )
{ good_matches.push_back( matches[i]);
}
}
Mat img_matches1;
drawMatches( Bild1, keypoints_1, Bild2, keypoints_2,
good_matches, img_matches1, Scalar::all(-1), Scalar::all(-1),
vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//bis hierhin geht es
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
std::vector< Point2f > obj1;
std::vector< Point2f > scene1;
for( int i = 0; i < good_matches.size(); i++ )
{
//-- Get the keypoints from the good matches
obj1.push_back( keypoints_1[ good_matches[i].queryIdx ].pt );
scene1.push_back( keypoints_2[ good_matches[i].trainIdx ].pt );
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
// Find the Homography Matrix
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%#
Mat H;
H= findHomography( scene1, obj1, CV_RANSAC,5 );
std::vector<Point2f> obj_corners(4);
obj_corners[0] = cvPoint(0,0); obj_corners[1] = cvPoint( Bild1.cols, 0 );
obj_corners[2] = cvPoint( Bild1.cols, Bild1.rows ); obj_corners[3] = cvPoint( 0, Bild1.rows );
std::vector<Point2f> scene_corners(4);
perspectiveTransform( obj_corners, scene_corners, H);
//-- Show detected matches
//-- Draw lines between the corners (the mapped object in the scene - image_2 )
line( img_matches1, scene_corners[0] + Point2f( Bild1.cols, 0), scene_corners[1] + Point2f( Bild1.cols, 0), Scalar(0, 255, 0), 4 );
line( img_matches1, scene_corners[1] + Point2f( Bild1.cols, 0), scene_corners[2] + Point2f( Bild1.cols, 0), Scalar( 0, 255, 0), 4 );
line( img_matches1, scene_corners[2] + Point2f( Bild1.cols, 0), scene_corners[3] + Point2f( Bild1.cols, 0), Scalar( 0, 255, 0), 4 );
line( img_matches1, scene_corners[3] + Point2f( Bild1.cols, 0), scene_corners[0] + Point2f( Bild1.cols, 0), Scalar( 0, 255, 0), 4 );
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//Warp images
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Mat result;
warpPerspective(Bild2, result, H, Size(Bild2.cols*2, Bild2.rows), INTER_CUBIC);
Mat final(Size(Bild2.cols + Bild1.cols, Bild2.rows),CV_8UC3);//richtig //testen ob Spaltenanzahl auswirkungen auf das ergebnis hat
//velikost img1
Mat roi1(final, Rect(0, 0, Bild1.cols, Bild1.rows));
Mat roi2(final, Rect(0, 0, result.cols, result.rows));
result.copyTo(roi2);
Bild1.copyTo(roi1);
return final;
}
In my view I make some misstakes with the roi...
what can I do I try blending but it works only of the images have the same size...or I can remove the black part...What is the best thing I can do?
Maybe I copy one roi over another I try to change the order of
result.copyTo(roi2);
Bild1.copyTo(roi1);
In one case I saw the left picture and in the other case the right picture...how can I see both together?
best regards
I found one way (but its not a good way to do it).
Firstly you have stitch 2 images (called final1)
Secondly when u stitch final1 and image 3 you have to blend the rois then it works...and you have to play arround with alpha...
Mat blendo;
double alpha=0.3;
double beta = ( 1.0 - alpha );
addWeighted( roi1, alpha, roi2, beta, 0.0, blendo);