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Image Filtering

Convolution and correlation, predefined and custom filters, nonlinear filtering, edge-preserving filters


imfilter N-D filtering of multidimensional images
imgaussfilt 2-D Gaussian filtering of images
imgaussfilt3 3-D Gaussian filtering of 3-D images
fspecial Create predefined 2-D filter
imguidedfilter Guided filtering of images
normxcorr2 Normalized 2-D cross-correlation
wiener2 2-D adaptive noise-removal filtering
fibermetric Enhance elongated or tubular structures in image
medfilt2 2-D median filtering
medfilt3 3-D median filtering
ordfilt2 2-D order-statistic filtering
stdfilt Local standard deviation of image
rangefilt Local range of image
entropyfilt Local entropy of grayscale image
nlfilter General sliding-neighborhood operations
gabor Create Gabor filter or Gabor filter bank
imgaborfilt Apply Gabor filter or set of filters to 2-D image
imboxfilt 2-D box filtering of images
imboxfilt3 3-D box filtering of 3-D images
integralImage Calculate 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
bwareafilt Extract objects from binary image by size
bwpropfilt Extract objects from binary image using properties
padarray Pad array
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
convmtx2 2-D convolution matrix


Image Region Analyzer Browse and filter connected components in an image

Examples and How To

Spatial Domain

Filter Image using imfilter Function

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

Filter Multidimensional Images Using imfilter

This example shows how to filter the three color channels of an RGB image.

Filter Images Using Predefined Filters

This example shows how to create filters using the fspecial function that can be used with imfilter.

Filter Images on Region Properties Using Image Region Analyzer App

This example shows how to filter a binary image based on the properties of regions in the image.

Filter Images Using imfilter with Convolution

This example shows how to perform image filtering using convolution with imfilter.

Noise Removal

To remove noise in pixel intensity values, use linear filtering or adaptive filtering.

Perform Flash/No-flash Denoising with Guided Filter

This example shows how to use a guided filter to smooth an image, reducing noise, while preserving edges.

Apply Gaussian Smoothing Filters to Images

This example shows how to apply different Gaussian smoothing filters to images using the imgaussfilt function.

Segment Thermographic Image after Edge-Preserving Filtering

This example shows how to work with thermal images, demonstrating a simple segmentation.

Apply Multiple Filters to Integral Image

This example shows how to apply multiple box filters of varying sizes to an image using integral image filtering.

Reducing Noise in Image Gradients

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

Frequency Domain

Designing Linear Filters in the Frequency Domain

Discusses designing two-dimensional finite impulse response (FIR) filters. This section assumes you are familiar with working in the frequency domain.


What Is Image Filtering in the Spatial Domain?

Filtering is a technique for modifying or enhancing an image.

What is Guided Image Filtering?

The imguidedfilter function performs edge-preserving smoothing on an image, using the content of a second image, called a guidance image, to influence the filtering.

Integral Image

In an integral image, every pixel is the summation of the pixels above and to the left of it.

Two-Dimensional Finite Impulse Response (FIR) Filters

The Image Processing Toolbox™ software supports one class of linear filter: the two-dimensional finite impulse response (FIR) filter.

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