Pixel intensity values along imline segment in Matlab

Question

Consider an image displayed using Matlab imagesc() axes of some generic description, say 10x10 pixels, where each pixel has an intensity value in [0 255].

Using the imline() method in the image analysis toolkit I would like to retrieve the pixel intensity values along a line defined interactively by the user. Commonly known as a "line profile". The important difference here is that a line parallel to either X or Y axis is insufficient. The line has to be interactively drawn by the user.

So far I have looked into Matlab methods improfile() and impixel() but so far I have not managed to get the desired result.

improfile does exactly this. Where are you running into difficulty? — Peter
Maube with the interactive input. In that case look for callback actions for axes . — Crowley
@Crowley Callbacks for axes solved all my problems. Thank you. If you want me to up vote your suggestion post it as a solution. — Peter

Crowley Crowley · Accepted Answer · 2016-03-16T20:59:47

This is a piece of code that reads where the image (objectHandle) is clicked and updates the line (currentLine handle) value and string in textboxes (Coords handle).

%% Code here
axis tight
imageHandle = imshow('input\foo.jpg');
set(imageHandle,'ButtonDownFcn',{@ImageClickCallback,Coords,currentLine});
%% Code there

function ImageClickCallback (objectHandle,~,Coords,currentLine)
axesHandle  = get(objectHandle,'Parent');
coordinates = get(axesHandle,'CurrentPoint');   %// This line reads the click
coordinates = coordinates(1,1:2);
LineX=get(currentLine,'xdata');
LineY=get(currentLine,'ydata');
set(currentLine,'xdata',[LineX,coordinates(1)])
set(currentLine,'ydata',[LineY,coordinates(2)])

set(Coords.X,'string',{'X';num2str(coordinates(1),'%.0f')})
set(Coords.Y,'string',{'Y';num2str(coordinates(2),'%.0f')})

end

Pixel intensity values along imline segment in Matlab

1 Answers