images in Matlab

[MNS747]

Hi I am new to Matlab and what i am trying to do is to import an image(jpg) and trying to plot contours on it. when i imported the image, its size says
640 320 3
which i dont understand what '3'means.
Also when i am trying to plot contours using
'contourf' it comes up with several types of errors.
Error says
1) function 'contourc' is not defined for values of class 'uint8'.
2) some times it says the image has to be two dimensional.

i want to ask what does this two dimensional means as far as i think the image is a 2D image. For my own sonfirmation I made a 4X5 matrix and plotted it with 'contourf' and it worked fine but when i am doing the same for an image it doesnt work and comes up with errors mentioned above.As I have mentioned i am new to this, is it possible for any one of you to explain what mistake i am doing.
i would appreciate if i get any answers to this.
Regards

 

[SomptingGuy]

The 3 is probably red, green, blue.

To use contourc, cast your data, e.g. double(data). My ML version doesn't like float(data), but it is quite old.


- Steve

 

[MNS747]

Thanks Steve

That was a great help. Yes 3 is the depth of colours.
I will now try contourc.

Regards