Why imwarp isn’t working for cylindrical projection?
I am trying to find the cylindrical projection of an image using the cylindrical projection equations. After finding the warpped values for the X and Y corodinates, I am trying to use the inbuilt MATLAB imwarp function to project the image onto the new coordinates, so that I can use the interpolation for smooth image. However, I get a different warpped image. Here is the output what I am getting:
What I expect the image to be:
Below is the cylindrical projection code:
clc; close all; clear;
% Inputs
fileName = ‘checker.jpg’;
% Focal lengths
fx = 50;
fy = 50;
% Read image
image = (imread(fileName));
% Get image size
[ydim, xdim, bypixs] = size(image);
% Camera intrinsics
K = [fx, 0, xdim/2; 0, fy, ydim/2; 0, 0, 1];
% Distortion coefficients [k1, k2, k3, p1, p2]
DC = [0, 0, 0, 0, 0];
% Get distrotion coefficients
fx = K(1,1);
fy = K(2,2);
k1 = DC(1);
k2 = DC(2);
k3 = DC(3);
p1 = DC(4);
p2 = DC(5);
% Get image size
[ydim, xdim, bypixs] = size(image);
% Get the center of image
xc = xdim/2;
yc = ydim/2;
% Create X and Y coordinates grid
[X,Y] = meshgrid(1:xdim, 1:ydim);
% Perform the cylindrical projection
theta = (X – xc) / fx;
h = (Y – yc) / fy;
% Cylindrical coordinates to Cartesian
xcap = sin(theta);
ycap = h;
zcap = cos(theta);
xyz_cap = cat(3, xcap, ycap, zcap);
xyz_cap = reshape(xyz_cap,[],3);
% Normalized coords
xyz_cap_norm = (K * xyz_cap’)’;
xn = xyz_cap_norm(:,1) ./ xyz_cap_norm(:,3);
yn = xyz_cap_norm(:,2) ./ xyz_cap_norm(:,3);
% Radial and tangential distortion
r = xn.^2 + yn.^2;
xd_r = xn .* (1 + k1 * r.^2 + k2 * r.^4 + k3 * r.^6);
yd_r = yn .* (1 + k1 * r.^2 + k2 * r.^4 + k3 * r.^6);
xd_t = 2 * p1 * xn .* yn + p2 * (r.^2 + 2 * xn.^2);
yd_t = p1 * (r.^2 + 2 * yn.^2) + 2 * p2 * xn .* yn;
xd = xd_r + xd_t;
yd = yd_r + yd_t;
% Convert to 2D array
xd = reshape(ceil(xd),[ydim, xdim]);
yd = reshape(ceil(yd),[ydim, xdim]);
% Get projections
imageCylindrical = imwarp(image, cat(3,xd, yd), ‘cubic’);
imshow(imageCylindrical)
Please let me know what I am doing wrong using the imwarp function. Any help is appreciated!I am trying to find the cylindrical projection of an image using the cylindrical projection equations. After finding the warpped values for the X and Y corodinates, I am trying to use the inbuilt MATLAB imwarp function to project the image onto the new coordinates, so that I can use the interpolation for smooth image. However, I get a different warpped image. Here is the output what I am getting:
What I expect the image to be:
Below is the cylindrical projection code:
clc; close all; clear;
% Inputs
fileName = ‘checker.jpg’;
% Focal lengths
fx = 50;
fy = 50;
% Read image
image = (imread(fileName));
% Get image size
[ydim, xdim, bypixs] = size(image);
% Camera intrinsics
K = [fx, 0, xdim/2; 0, fy, ydim/2; 0, 0, 1];
% Distortion coefficients [k1, k2, k3, p1, p2]
DC = [0, 0, 0, 0, 0];
% Get distrotion coefficients
fx = K(1,1);
fy = K(2,2);
k1 = DC(1);
k2 = DC(2);
k3 = DC(3);
p1 = DC(4);
p2 = DC(5);
% Get image size
[ydim, xdim, bypixs] = size(image);
% Get the center of image
xc = xdim/2;
yc = ydim/2;
% Create X and Y coordinates grid
[X,Y] = meshgrid(1:xdim, 1:ydim);
% Perform the cylindrical projection
theta = (X – xc) / fx;
h = (Y – yc) / fy;
% Cylindrical coordinates to Cartesian
xcap = sin(theta);
ycap = h;
zcap = cos(theta);
xyz_cap = cat(3, xcap, ycap, zcap);
xyz_cap = reshape(xyz_cap,[],3);
% Normalized coords
xyz_cap_norm = (K * xyz_cap’)’;
xn = xyz_cap_norm(:,1) ./ xyz_cap_norm(:,3);
yn = xyz_cap_norm(:,2) ./ xyz_cap_norm(:,3);
% Radial and tangential distortion
r = xn.^2 + yn.^2;
xd_r = xn .* (1 + k1 * r.^2 + k2 * r.^4 + k3 * r.^6);
yd_r = yn .* (1 + k1 * r.^2 + k2 * r.^4 + k3 * r.^6);
xd_t = 2 * p1 * xn .* yn + p2 * (r.^2 + 2 * xn.^2);
yd_t = p1 * (r.^2 + 2 * yn.^2) + 2 * p2 * xn .* yn;
xd = xd_r + xd_t;
yd = yd_r + yd_t;
% Convert to 2D array
xd = reshape(ceil(xd),[ydim, xdim]);
yd = reshape(ceil(yd),[ydim, xdim]);
% Get projections
imageCylindrical = imwarp(image, cat(3,xd, yd), ‘cubic’);
imshow(imageCylindrical)
Please let me know what I am doing wrong using the imwarp function. Any help is appreciated! I am trying to find the cylindrical projection of an image using the cylindrical projection equations. After finding the warpped values for the X and Y corodinates, I am trying to use the inbuilt MATLAB imwarp function to project the image onto the new coordinates, so that I can use the interpolation for smooth image. However, I get a different warpped image. Here is the output what I am getting:
What I expect the image to be:
Below is the cylindrical projection code:
clc; close all; clear;
% Inputs
fileName = ‘checker.jpg’;
% Focal lengths
fx = 50;
fy = 50;
% Read image
image = (imread(fileName));
% Get image size
[ydim, xdim, bypixs] = size(image);
% Camera intrinsics
K = [fx, 0, xdim/2; 0, fy, ydim/2; 0, 0, 1];
% Distortion coefficients [k1, k2, k3, p1, p2]
DC = [0, 0, 0, 0, 0];
% Get distrotion coefficients
fx = K(1,1);
fy = K(2,2);
k1 = DC(1);
k2 = DC(2);
k3 = DC(3);
p1 = DC(4);
p2 = DC(5);
% Get image size
[ydim, xdim, bypixs] = size(image);
% Get the center of image
xc = xdim/2;
yc = ydim/2;
% Create X and Y coordinates grid
[X,Y] = meshgrid(1:xdim, 1:ydim);
% Perform the cylindrical projection
theta = (X – xc) / fx;
h = (Y – yc) / fy;
% Cylindrical coordinates to Cartesian
xcap = sin(theta);
ycap = h;
zcap = cos(theta);
xyz_cap = cat(3, xcap, ycap, zcap);
xyz_cap = reshape(xyz_cap,[],3);
% Normalized coords
xyz_cap_norm = (K * xyz_cap’)’;
xn = xyz_cap_norm(:,1) ./ xyz_cap_norm(:,3);
yn = xyz_cap_norm(:,2) ./ xyz_cap_norm(:,3);
% Radial and tangential distortion
r = xn.^2 + yn.^2;
xd_r = xn .* (1 + k1 * r.^2 + k2 * r.^4 + k3 * r.^6);
yd_r = yn .* (1 + k1 * r.^2 + k2 * r.^4 + k3 * r.^6);
xd_t = 2 * p1 * xn .* yn + p2 * (r.^2 + 2 * xn.^2);
yd_t = p1 * (r.^2 + 2 * yn.^2) + 2 * p2 * xn .* yn;
xd = xd_r + xd_t;
yd = yd_r + yd_t;
% Convert to 2D array
xd = reshape(ceil(xd),[ydim, xdim]);
yd = reshape(ceil(yd),[ydim, xdim]);
% Get projections
imageCylindrical = imwarp(image, cat(3,xd, yd), ‘cubic’);
imshow(imageCylindrical)
Please let me know what I am doing wrong using the imwarp function. Any help is appreciated! matlab, imwarp, image processing MATLAB Answers — New Questions