ImageFilter

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`ImageFilter`

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ImageFilter[f,image,r]

applies the function f to the range-r neighborhood of each pixel in each channel of image.

Details and Options

ImageFilter is a generic neighborhood operator that replaces the value of each pixel by the result of applying a function to a pixel neighborhood. It can be used to implement linear or nonlinear local filters.

ImageFilter works with 2D and 3D images with any number of channels, operating separately on each channel.
ImageFilter[f,image,{r₁,r₂,…}] applies f to blocks centered on each pixel.
ImageFilter assumes the index coordinate system for lists and images.

The channel values supplied to f are normally in the range 0 to 1, regardless of the underlying type used in the Image object. The function f is assumed to return channel values that are normally in the range 0 to 1.
ImageFilter[f,image, r] returns an image of the same type as image.
The following options can be given:

	Interleaving	False	whether to supply f lists of channel values
	Masking	All	region of interest
	Padding	"Fixed"	what values to assume beyond the image

With the default setting Interleaving->False, the elements in the arrays to which f is applied are individual channel values for the pixels.
With Interleaving->True, the elements are instead the list of all channel values for a particular pixel.
ImageFilter by default gives an image of the same dimensions as image.
With a setting Padding->None, ImageFilter[f,image,…] normally gives an image smaller than image.

Examples

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Basic Examples (1)Summary of the most common use cases

Blur an image by replacing each pixel with the local mean:

In[2]:=2

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https://wolfram.com/xid/0puzjrxc0q-r6t8nl

Out[2]=2

Scope (4)Survey of the scope of standard use cases

Apply a local minimum filter to a binary image:

In[13]:=13

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https://wolfram.com/xid/0puzjrxc0q-l61xc

Out[13]=13

Apply a median filter to a grayscale image:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-e9jcgi

Out[1]=1

Apply a median filter to a color image:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-46u81

Out[1]=1

Apply a local maximum filter to a 3D image:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-ebb8tu

Out[1]=1

Options (5)Common values & functionality for each option

Interleaving (1)

When filtering a color image, the filter is applied to each channel separately:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-f87g5h

Out[1]=1

Filter over all channels:

In[2]:=2

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https://wolfram.com/xid/0puzjrxc0q-uwim2a

Out[2]=2

Masking (1)

Process the area outside a disk:

In[2]:=2

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https://wolfram.com/xid/0puzjrxc0q-ypbqrw

Out[2]=2

Padding (3)

By default, a "Fixed" padding is used:

In[6]:=6

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https://wolfram.com/xid/0puzjrxc0q-cczurx

Out[6]=6

Pad with zero:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-ndcxe0

Out[1]=1

No padding results in a smaller image:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-c0tfb1

Out[1]=1

Applications (3)Sample problems that can be solved with this function

Find the exact position of an image fragment:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-iskikh

Out[1]=1

Create a mean filter using a line kernel:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-y0hfv

Out[1]=1

Median deviation filter:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-wuv8b8

Out[1]=1

Properties & Relations (2)Properties of the function, and connections to other functions

Morphological dilation using ImageFilter:

In[29]:=29

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https://wolfram.com/xid/0puzjrxc0q-jnxuw1

Out[29]=29

Use ImageFilter to perform a convolution:

In[1]:=1

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https://wolfram.com/xid/0puzjrxc0q-rwu1ov

Out[1]=1

For images of real types, this is equivalent to ImageConvolve:

In[2]:=2

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https://wolfram.com/xid/0puzjrxc0q-lgyhg3

Out[2]=2

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