radon (Image Processing Toolbox)

Radon transform

Syntax

```
R = radon(I,theta)
[R,xp] = radon(...)
```

Description

The radon function computes the Radon transform, which is the projection of the image intensity along a radial line oriented at a specified angle.

R = radon(I,theta) returns the Radon transform of the intensity image I for the angle theta degrees. If theta is a scalar, the result R is a column vector containing the Radon transform for theta degrees. If theta is a vector, then R is a matrix in which each column is the Radon transform for one of the angles in theta. If you omit theta, it defaults to 0:179.

[R,xp] = radon(...) returns a vector xp containing the radial coordinates corresponding to each row of R.

Class Support

I can be of class double, logical, or of any integer class. All other inputs and outputs are of class double.

Remarks

The radial coordinates returned in xp are the values along the x'-axis, which is oriented at theta degrees counterclockwise from the x-axis. The origin of both axes is the center pixel of the image, which is defined as

```
floor((size(I)+1)/2)
```

For example, in a 20-by-30 image, the center pixel is (10,15).

Example

iptsetpref('ImshowAxesVisible','on')
I = zeros(100,100);
I(25:75,25:75) = 1;
theta = 0:180;
[R,xp] = radon(I,theta);
imshow(theta,xp,R,[],'notruesize'), colormap(hot), colorbar

See Also

iradon, phantom

References

Bracewell, Ronald N. Two-Dimensional Imaging. Englewood Cliffs, NJ: Prentice Hall, 1995. pp. 505-537.

Lim, Jae S. Two-Dimensional Signal and Image Processing. Englewood Cliffs, NJ: Prentice Hall, 1990. pp. 42-45.

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