Guided filtering of images
B = imguidedfilter(A,G)
B = imguidedfilter(A)
B = imguidedfilter(__,Name,Value,...)
This example shows how to perform edge-preserving smoothing using a guided filter.
Read an image into the workspace. Display the image.
A = imread('pout.tif'); imshow(A);
Smooth the image using
imguidedfilter. In this syntax,
imguidedfilter uses the image itself as the guidance image.
Iguided = imguidedfilter(A);
For comparison, smooth the original image using a gaussian filter defined by
imgaussfilt. Set the standard deviation of the filter to 2.5 so that the degree of smoothing approximately matches that of the guided filter.
Igaussian = imgaussfilt(A,2);
Display the result of guided filtering and the result of gaussian filtering.
Observe that the flat regions of the two filtered images, such as the jacket and the face, have similar amounts of smoothing. However, the guided filtered image better preserves the sharpness of edges, such as around the trellis and the collar of the white shirt.
A— Image to be filtered
Image to be filtered, specified as a nonsparse, binary, grayscale, or RGB image.
G— Image to use as a guide during filtering
Image to use as a guide during filtering, specified as a nonsparse, binary, grayscale, or RGB image.
comma-separated pairs of
the argument name and
Value is the corresponding value.
Name must appear inside quotes. You can specify several name and value
pair arguments in any order as
Ismooth = imguidedfilter(A,'NeighborhoodSize',[4 4]);
'NeighborhoodSize'— Size of the rectangular neighborhood around each pixel used in guided filtering
[5 5](default) | scalar or two-element vector of positive integers
Size of the rectangular neighborhood around each pixel used in guided filtering, specified as
a scalar or a two-element vector,
N], of positive integers. If you specify
a scalar value, such as
neighborhood is a square of size
Q] Do not specify a value greater than
the size of the image.
Ismooth = imguidedfilter(A,'NeighborhoodSize',[4
'DegreeOfSmoothing'— Amount of smoothing in the output image
0.01*diff(getrangefromclass(G)).^2(default) | positive scalar
Amount of smoothing in the output image, specified as a positive scalar. If you specify a small value, only neighborhoods with small variance (uniform areas) will get smoothed and neighborhoods with larger variance (such as around edges) will not be smoothed. If you specify a larger value, high variance neighborhoods, such as stronger edges, will get smoothed in addition to the relatively uniform neighborhoods. Start with the default value, check the results, and adjust the default up or down to achieve the effect you desire.
a soft threshold on variance for the given neighborhood. If a pixel's
neighborhood has variance much lower than the threshold, it will see
some amount of smoothing. If a pixel's neighborhood has variance
much higher than the threshold it will have little to no smoothing.
have different number of channels.
A is an
G is a grayscale or binary image,
guidance for all the channels of
imguidedfilter uses each channel of
guidance for the corresponding channel of
A is a grayscale or binary
G is an RGB image,
all the three channels of
G for guidance (color
statistics) for filtering
 Kaiming He, Jian Sun, Xiaoou Tang, Guided Image Filtering. IEEE Transactions on Pattern Analysis and Machine Intelligence, Volume 35, Issue 6, pp. 1397-1409, June 2013