# How to convert image to cylindrical shape?

Hello,

I am using objective c language.

I want to convert my image to cylindrical shape. Here I am using below cpp file code to convert image.

```
cv::Mat CylindricalWarper2 (Mat img)
{
cv::Mat destImgMat(img.size(), CV_8U);
for(int y = 0; y < img.rows; y++)
{
for(int x = 0; x < img.cols; x++)
{
cv::Point2f current_pos(x,y);
current_pos = convert_pt1dd(current_pos, img.cols, img.rows);
cv::Point2i top_left((int)current_pos.x,(int)current_pos.y);
if(top_left.x < 0 || top_left.x > img.cols-2 || top_left.y < 0 ||
top_left.y > img.rows-2)
{
continue;
}
//bilinear interpolation
float dx = current_pos.x-top_left.x;
float dy = current_pos.y-top_left.y;
float weight_tl = (1.0 - dx) * (1.0 - dy);
float weight_tr = (dx) * (1.0 - dy);
float weight_bl = (1.0 - dx) * (dy);
float weight_br = (dx) * (dy);
uchar value = weight_tl * img.at<uchar>(top_left) +
weight_tr * img.at<uchar>(top_left.y,top_left.x+1) +
weight_bl * img.at<uchar>(top_left.y+1,top_left.x) +
weight_br * img.at<uchar>(top_left.y+1,top_left.x+1);
destImgMat.at<uchar>(y,x) = value;
}
}
return destImgMat;
}
cv::Point2f convert_pt1dd(cv::Point2f point,int w,int h)
{
cv::Point2f pc(point.x-w/2,point.y-h/2);
float f = w;
float r = w;
float omega = w/2;
float z0 = f - sqrt(r*r-omega*omega);
float zc = (2*z0+sqrt(4*z0*z0-4*(pc.x*pc.x/(f*f)+1)*(z0*z0-r*r)))/(2*
(pc.x*pc.x/(f*f)+1));
cv::Point2f final_point(pc.x*zc/f,pc.y*zc/f);
final_point.x += w/2;
final_point.y += h/2;
return final_point;
}
```

With this code I got the cylindrical shape but my image cut down. Not get the full cylindrical projection image, My image look like below,

I want to display my full image in cylindrical shape. If some source or help provided, greatly Appreciated.

Thanks in advance

Take a look here as it seems his code is working properly.

Oh and btw, there is actually a cylindrical warping class, so it might do exactly what you are doing manually and it might be more optimized!