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图像变换

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

An image transform converts an image from one domain to another. Images are usually acquired and displayed in the spatial domain, in which adjacent pixels represent adjacent parts of the scene. However, images can also be acquired in other domains, such as the frequency domain in which adjacent pixels represent adjacent frequency components, or the Hough domain in which adjacent pixels represent adjacent projection angles and radial distances. Viewing and processing an image in nonspatial domains can enable the identification of features that are less easily detected in the spatial domain.

Functions

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逆离散余弦变换
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 零频移

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.

  • Radon Transform

    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 Transformation

    逆伦转换从许多投影角度从一组平行梁投影数据中重建图像。

  • 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.