图像变换

执行傅里叶、离散余弦、霍夫、拉东和扇形波束变换

图像变换将图像从一个域转换到另一个域。图像通常在空间域中获取和显示，其中相邻像素表示场景的相邻部分。不过，也可以在其他域中获取图像，例如其中相邻像素表示相邻频率分量的频域，或其中相邻像素表示相邻投影角度和径向距离的霍夫域。在非空间域中查看和处理图像可以识别在空间域中不容易检测到的特征。

函数

`hough`	霍夫变换
`houghlines`	基于霍夫变换提取线段
`houghpeaks`	识别霍夫变换中的峰值
`radon`	拉东变换
`iradon`	Inverse Radon transform
`fanbeam`	Fan-beam transform
`ifanbeam`	Inverse fan-beam transform
`fan2para`	Convert fan-beam projections to parallel-beam
`para2fan`	Convert parallel-beam projections to fan-beam
`fft2`	二维快速傅里叶变换
`fftshift`	将零频分量移到频谱中心
`ifft2`	二维快速傅里叶逆变换
`ifftshift`	逆零频平移
`dct2`	二维离散余弦变换
`idct2`	二维逆离散余弦变换
`dctmtx`	离散余弦变换矩阵

傅里叶变换
了解傅里叶变换及其在图像处理中的一些应用，尤其是在图像滤波中。
离散余弦变换
了解图像的离散余弦变换 (DCT) 及其应用，特别是在图像压缩中的应用。
霍夫变换
霍夫变换检测二值图像中的线条，包括从垂直和水平方向以任意角度倾斜的线条。
Radon Transform
The Radon transform calculates parallel-beam projections of a grayscale image at different rotation angles, typically for use in tomographic reconstruction.
The Inverse Radon Transformation
The inverse Radon transform reconstructs an image from a set of parallel-beam projection data across many projection angles.
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.
Principal Component Analysis of Images
Principal component analysis (PCA) is a statistical technique used to reduce the number of variables per sample, also known as the dimensionality, of large data sets while preserving as much important information as possible. (自 R2026a 起)