CODEWITHSUNDEEP
imagematlab
PhD Ma
PhD Ma

Reputation: 107

How to used linspace matlab function to get the and the y of all pixels in image?

I have an image of 200x200 * 3, and I should to find the x and the y of each pixel of the image by using the linspace Matlab function. I have already used the mesh grid function with the following code:

Ny=200; % # pixels in y direction 
Nx=200; % # pixels in x direction 
resolution=1; % size of a pixel 
img=rand(Ny,Nx,3); % random image 
y=(img(1:Ny))*resolution-resolution/2; 
x=(img(1:Nx))*resolution-resolution/2; 
[x,y]=meshgrid(x,y);

But my supervisor told me to use the function linspace and I cannot understand how.Can someone help me please

Upvotes: 1

Views: 347

Answers (1)

beaker
beaker

Reputation: 16801

The only reason I can think of that your supervisor wants you to use linspace is for creating the x and y vector inputs to meshgrid. linspace alone is not sufficient to generate all of the pixel coordinates, so you'll have to use meshgrid, ndgrid, repelem or repmat.

The one advantage that linspace has over simply doing something like 1:resolution:Ny is that linspace ensures that the endpoints always appear in the range. For example, if you do

>> 1:.37:4
ans =
    1.0000    1.3700    1.7400    2.1100    2.4800    2.8500    3.2200    3.5900    3.9600

you don't get 4 as the last point. However, if you use linspace:

>> linspace(1,4,9)
ans =
   1.0000   1.3750   1.7500   2.1250   2.5000   2.8750   3.2500   3.6250   4.0000

the spacing is automatically adjusted to make the last element 4.

So assuming that resolution is the multiplier for the number of points you want, for 2 you want 401 evenly spaced points and for 1/2 you want 101 points, your code would look something like this:

x_points = linspace(1, Nx, Nx*resolution+1);
y_points = linspace(1, Ny, Ny*resolution+1);

(I'm still not sure what the resolution/2 part is supposed to do, so we'll need to clarify that.)

Then you would pass those to meshgrid:

[X,Y] = meshgrid(x_points, y_points);

Upvotes: 2

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