图像滤波

卷积和相关性、预定义和自定义滤波器、非线性滤波、边缘保持滤波器

滤波是一种用于修正或增强图像的技术。例如，您可以对图像进行滤波以强调某些特征或删除其他特征。用滤波实现的图像处理运算包括平滑、锐化和边缘增强。

App

Browse and filter connected components in an image

函数

设计图像滤波器

`fspecial`	创建预定义的二维滤波器
`fspecial3`	Create predefined 3-D filter
`convmtx2`	2-D convolution matrix

空间域中的基本图像滤波

`imfilter`	多维图像的 N 维滤波
`roifilt2`	Filter region of interest (ROI) in image
`nlfilter`	General sliding-neighborhood operations
`imgaussfilt`	图像的二维高斯滤波
`imgaussfilt3`	3-D Gaussian filtering of 3-D images
`wiener2`	二维自适应去噪滤波
`medfilt2`	二维中位数滤波
`medfilt3`	3-D median filtering
`modefilt`	2-D and 3-D mode filtering
`ordfilt2`	2-D order-statistic filtering
`stdfilt`	Local standard deviation of image
`rangefilt`	Local range of image
`entropyfilt`	Local entropy of grayscale image
`imboxfilt`	2-D box filtering of images
`imboxfilt3`	3-D box filtering of 3-D images
`fibermetric`	Enhance elongated or tubular structures in image
`maxhessiannorm`	Maximum of Frobenius norm of Hessian of matrix
`padarray`	填充数组

边缘保持滤波

`imbilatfilt`	Bilateral filtering of images with Gaussian kernels
`imdiffuseest`	Estimate parameters for anisotropic diffusion filtering
`imdiffusefilt`	Anisotropic diffusion filtering of images
`imguidedfilter`	Guided filtering of images
`imnlmfilt`	Non-local means filtering of image
`burstinterpolant`	Create high-resolution image from set of low-resolution burst mode images

纹理滤波

`gabor`	Create Gabor filter or Gabor filter bank
`imgaborfilt`	将 Gabor 滤波器或滤波器组应用于二维图像

按属性特征滤波

`bwareafilt`	按大小从二值图像中提取对象
`bwpropfilt`	Extract objects from binary image using properties

积分图像域滤波

`integralImage`	Calculate 2-D integral image
`integralImage3`	Calculate 3-D integral image
`integralBoxFilter`	2-D box filtering of integral images
`integralBoxFilter3`	3-D box filtering of 3-D integral images

频域滤波

`freqspace`	频率响应的频率间距
`freqz2`	2-D frequency response
`fsamp2`	2-D FIR filter using frequency sampling
`ftrans2`	2-D FIR filter using frequency transformation
`fwind1`	2-D FIR filter using 1-D window method
`fwind2`	2-D FIR filter using 2-D window method

主题

空间域中的图像滤波入门

什么是空间域中的图像滤波？

在经过空间滤波的图像中，每个输出像素的值是相邻输入像素的加权和。权重由称为卷积核或滤波器的矩阵提供。

Filter Grayscale and Truecolor (RGB) Images using imfilter Function

This example shows how to filter an image with a 5-by-5 averaging filter containing equal weights.

Filter Images Using Predefined Filter

This example shows how to create a type of special filter called an unsharp masking filter, which makes edges and detail in an image appear sharper.

imfilter 边界填充选项

当卷积或相关性核的一部分超出图像边缘时，可以通过对图像进行零填充或复制边界像素来外插图像值。

去噪滤波

去除噪声

噪声是指在图像采集或传输过程中出现的像素值的随机误差。去除噪声可以提高图像质量。

将高斯平滑滤波器应用于图像

此示例说明如何使用不同强度的高斯平滑滤波器来对图像进行模糊处理。该示例包括各向同性和各向异性高斯滤波。

Reduce Noise in Image Gradients

This example shows how to reduce noise associated with computing image gradients.

边缘保持滤波

什么是引导图像滤波？

引导图像滤波对图像执行边缘保持平滑处理。它使用第二个图像（称为引导图像）的内容来影响滤波。

Perform Flash/No-flash Denoising with Guided Filter

This example shows how to reduce noise from an image while using a guidance image to preserve the sharpness of edges.

Segment Thermographic Image after Edge-Preserving Filtering

This example shows how to segment a hot object from the background in a thermographic image.

积分图像域滤波

Integral Image

Integral images are a quick way to represent images for filtering. In an integral image, the value of each pixel is the summation of the pixels above and to the left of it.

Apply Multiple Filters to Integral Image

This example shows how to smooth an image by different amounts by applying box filters of varying sizes to the integral image.

频域滤波

Design Linear Filters in the Frequency Domain

You can design filters that modify the frequency content of images. Filtering in the frequency domain is often faster than filtering in the spatial domain.