Examining pixel values


Instead of just displaying values of individual pixels I can display the values of the pixels along a line in the scene. Let’s have a look at this.

To do that I use the line button here and I click the first point here and I am going to click a second point over here. Draws a line on the original image and in the other window we see what we call an intensity profile. So we can see that the intensity is initially quite bright—we’re on the wall—then as we move further towards the right along that line the intensity drops, gets quite dark in the doorway. If you come out of the doorway and cross a section of wall again the pixel values have got a large value, it is a bright wall, and then they fall down to a lower value as we go through the next window.

So, this is the pattern of pixel values as we move along a line within the original scene.

Another thing we can do is to create what is called a region of interest, effectively to zoom in onto a rectangular region within the image. So let’s have a look at that. What I will do is I will remove this profile image and I will click the zoom button, and I will lasso an area of the image interactively and the result is a smaller image which contains a sub region of the original image.

We can use MATLAB to extract a region of interest from an image, or to display a profile of brightness along a line in the image.

Professor Peter Corke

Professor of Robotic Vision at QUT and Director of the Australian Centre for Robotic Vision (ACRV). Peter is also a Fellow of the IEEE, a senior Fellow of the Higher Education Academy, and on the editorial board of several robotics research journals.

Skill level

This content assumes an understanding of high school-level mathematics, e.g. trigonometry, algebra, calculus, physics (optics) and some knowledge/experience of programming (any language).

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