How to find z coordinate while having only x and y coordinates on images?

Hi, im looking a z-coordinate on an 2D image that I already use a mesh to find diameter on 3D graph. Here i attach my codes that i try on this link.

I = imread ("01_manual1.gif");
edtImage = 2 * bwdist(~I);
skel = bwmorph(I, 'skel', Inf);
diameterImage = edtImage .* double(skel);
mesh (diameterImage);

Next, i already have x and y coordinate but i have to get the z coordinate without referring to the graph which is automatically find the z.

Here my x and y coordinates.

    x     y
    78   198
   145   238
    26   268
    94   198
    35   292
   111   202
   138   294
    57   205
    49   307
    50   210
    68   318
   136   221
    37   223
   147   246
   149   258
    29   280
    97   320
    86   321

i want to find the z coordinate to plot a point on the 3d graph sing plot3. I hope anyone can help me or suggest me a better method. Thank you.

Answer 1

[KSSV]

Read about interp2

[Nasiruddin Zh]

i already read that but i didnt understand how can i do with the query points which is xq and yq.

[Nasiruddin Zh]

hi, thank you for your suggestion. i already got the data by using this.

z = interp2(diameterImage, x, y);

Answer 2

[Image Analyst]

If you have x and y (as you said) then you can get the diameter (Z) by

diameterZ = diameterImage (y, x);

[Nasiruddin Zh]

if im using that i will get 18 * 18 matrix.

let say im adding this.

mesh (diameterImage);
hold on; plot(x,y,'+k','MarkerSize',10,'Color','r','LineWidth',1.5);
hold off

diameterZ = diameterImage (x,y);

i want the z coordinate only at 18*1 matrix from the x and y above.