# Documentation

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# Image Transforms

Perform Fourier, discrete cosine, Radon, and fan-beam transforms

## Functions

 `bwdist` Distance transform of binary image `bwdistgeodesic` Geodesic distance transform of binary image `graydist` Gray-weighted distance transform of grayscale image `hough` Hough transform `houghlines` Extract line segments based on Hough transform `houghpeaks` Identify peaks in Hough transform `dct2` 2-D discrete cosine transform `dctmtx` Discrete cosine transform matrix `fan2para` Convert fan-beam projections to parallel-beam `fanbeam` Fan-beam transform `idct2` 2-D inverse discrete cosine transform `ifanbeam` Inverse fan-beam transform `iradon` Inverse Radon transform `para2fan` Convert parallel-beam projections to fan-beam `radon` Radon transform `fft2` 2-D fast Fourier transform `fftshift` Shift zero-frequency component to center of spectrum `ifft2` 2-D inverse fast Fourier transform `ifftshift` Inverse zero-frequency shift

## Topics

Fourier Transform

Learn about the Fourier transform and some of its applications in image processing, particularly in image filtering.

Discrete Cosine Transform

Learn about the discrete cosine transform (DCT) of an image and its applications, particularly in image compression.

Hough Transform

The Hough transform detects lines in an image, including lines tilted at arbitrary angles from vertical and horizontal. The Hough transform tends to be quick, but can exhibit artifacts.

The Radon transform detects lines in an image, including lines tilted at arbitrary angles from vertical and horizontal. The Radon transform tends to be more accurate at the cost of longer computation time.

The inverse Radon transform reconstructs an image from a set of parallel-beam projection data across many projection angles.

Detect Lines Using the Radon Transform

This example shows how to detect lines and identify the strongest lines in an image using the Radon transform.

Fan-Beam Projection

Use fan-beam projection and reconstruction when projections of an image are acquired along paths radiating from a point source. Medical tomography is a common application of fan-beam projection.