How to plot a graph of a line of pixels of an image showing black to white intensity across it.

Hi, I am completely new to Matlab and quickly need to use it to analyse an image I have. The image is black and white from a photo of 256 by 256 pixels and contains a beam. I would like to be able to specify a line of pixels across the image and plot a graph of the variation of white to black as I go along these pixels which should show a curve where my black beam is on a white(ish) background.

This image is obtained from a fourier transform (fft1) which makes the image greyscale (I think). I was told that typing 'plot(fft1(1,1:255))' is a good place to start from but it doesn't seem to plot a useful curve.

I have been told this is easy to do although I haven't found any relevant information, Any help would be much appreciated! Thanks, Graham

Answer 1

[David Young]

If you have the Image Processing Toolbox, have a look at improfile.

[Graham Boag]

Great thanks, this seems to be exactly what I need. Sorry to be a pain (I'm not familiar with the mathematics behind these functions) but I am a little unsure how to specify the coordinates using the c=improfile(I,xi,yi) function. I can use the c=improfile(n) function and pick a line but its not precise. Also, when I use 'plot (c)' it plots the graph onto my image so is there a little trick to making the plot onto a new graph? Thanks again and sorry if these questions are a little basic! Graham

[Jan]

To plot in a ne graph, open a new figure at first: "figure; plot(1:10);".

[Graham Boag]

Excellent thanks, I see how to use the figure and plot functions - Now I just need to figure out how to use the co-ordinates for the improfile function. I trust that I is the image I want to use, xi and yi seem to be vectors but if I want to plot a line from my image of co-ordinates say...(1,30) to (50,30) how would this translate to the xi and yi required for the function?