Cylindrical to rectangular correction in image processing

Dear All;

if have an image for cylindrical object ( say pipe). when take the image of the pipe it will project as rectangular image ,which may lead to projection error, how i can compensate for that.\

Best Regards;

Answer 1

[Adam Wyatt]

Create projected co-ordinates of original image

[Ny, Nx] = size(Img);
x = (1:Nx).';
y = (1:Ny).';

Create original co-ordinates of orignal image (you need to know the transfer function - you probably want to look up Mercator projection

[x1, y1] = MyCoordinateTransferFunction(x, y);

Create new co-ordinates on uniform grid

x2 = linspace(min(x1), max(x1), Nx).';
y2 = linspace(min(y1), max(y1), Ny).';

Interpolate image on new uniform grid

Img2 = interp2(x1.', y1, Img, x2.', y2, 'spline');

Note that I've defined the vectors as columns, so had to transpose the x-coordinates. Also, I've used spline interpolation - you could use linear or nearest if your want better speed but lower accuracy. Check the documentation.

[mustafa alnasser]

Thank You Adam for kind support

I am trying to follow to your code but i am not familiar how to implement Mercator projection for image , the code is as follow: clc; clear;

%Create projected co-ordinates of original image

[Ny, Nx] = size('001.jpg'); x = (1:Nx).'; y = (1:Ny).'; %Create original co-ordinates of orignal image (you need to know the transfer function - you probably want to look up Mercator projection

[x1, y1] = mercator(x, y); %Create new co-ordinates on uniform grid

x2 = linspace(min(x1), max(x1), Nx).'; y2 = linspace(min(y1), max(y1), Ny).'; Interpolate image on new uniform grid Img2 = interp2(x1.', y1, Img, x2.', y2, 'spline');

but there is a problem in the number of parameters as shown below:

Error using applyProjection (line 15) Incorrect number of arguments.

Error in mercator (line 38) varargout = applyProjection(mproj, varargin{:});

Error in imagecorrec (line 11) [x1, y1] = mercator(x, y);