Loren on the Art of MATLAB

Turn ideas into MATLAB

Tire Rotation 8

Posted by Loren Shure,

If only rotating tires were really this easy! After graduate school, I drove east for my post-doc at Woods Hole Oceanographic Institution. In late winter, I noticed that my tires still had red dust on them from visiting national parks in Utah. So I took a picture and later realized that my tire wasn't oriented for easily reading the make of the car.

Contents

Some Simple Image Processing

Today I am going to use some features from Image Processing Toolbox. You might also benefit from reading Steve's blog on image processing.

Read an Image

Here's a gray-scale image of my tire photo.

I = imread('tire.tif');
whos I
colormap(gray(256))
image(I), axis image, axis off
  Name        Size             Bytes  Class    Attributes

  I         205x232            47560  uint8              

Crop the Image

Next I want to select the hub to look at it more closely. I happen to know that region I want to look at, having already used imcrop interactively earlier to isolate the central portion.

rect = [90 74 41 41]
midI = imcrop(I,rect);
image(midI), axis image, axis off
rect =
    90    74    41    41

Resize the Image

Next, I want to resize the image so I can see details better.

midI5 = imresize(midI,5);
imshow(midI5)

Rotate the Image

Looking at the function imrotate, I see I specify the rotation I want in a counterclockwise sense. Eyeballing the angle, I choose 135 degrees.

midI5r = imrotate(midI5, 135);
imshow(midI5r)

Check the Tire Rotation

Here's the rotated tire. Now you know what kind of car I drove across the country some years ago.

Ir = imrotate(I,135);
imshow(Ir)

Quick Ideas?

Like today's blog, I occasionally enjoy trying out products in addition to MATLAB, in part so I can learn more about a particular domain or discipline. Have you used MATLAB or other MathWorks tools to teach yourself about some new technology or application? If so, please let me know here.


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Published with MATLAB® 7.5

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