Java DIP Applying Box Filter - Digital image processing

How to apply box filter?

Box filter is used to blur an image. A Box filter can be of various dimensions 3x3, 5x5, 9x9 etc.

You can use OpenCV function filter2D to perfom apply Box filter to images. You can find it under Imgproc package. Its syntax is given below:

The function arguments are described below:

Sr.No. Arguments
1

src

It is source image.

2

dst

It is destination image.

3

ddepth

It is the depth of dst. A negative value (such as -1) indicates that the depth is the same as the source.

4

kernel

It is the kernel to be scanned through the image.

5

anchor

It is the position of the anchor relative to its kernel. The location Point (-1, -1) indicates the center by default.

6

delta

It is a value to be added to each pixel during the convolution. By default it is 0.

7

BORDER_DEFAULT

We let this value by default.

Other than the filter2D() method, the other methods offered by the Imgproc class are described as briefly:

Sr.No. Methods
1

cvtColor(Mat src, Mat dst, int code, int dstCn)

It converts an image from one color space to another.

2

dilate(Mat src, Mat dst, Mat kernel)

It dilates an image by using a specific structuring element.

3

equalizeHist(Mat src, Mat dst)

It equalizes the histogram of a grayscale image.

4

filter2D(Mat src, Mat dst, int ddepth, Mat kernel, Point anchor, double delta)

It convolves an image with the kernel.

5

GaussianBlur(Mat src, Mat dst, Size ksize, double sigmaX)

It blurs an image using a Gaussian filter.

6

integral(Mat src, Mat sum)

It calculates the integral of an image.

Example

Below mentioned example describes about the use of Imgproc class to apply Box filter to an image of Grayscale.

Output

After executing the above code, the following output is seen:

Original Image

original

Following example describes about how to convolve our image with the following filter (kernel) which will resulted in blurring an image as its size increases.

This original image has been convolved with the box filter of size 5, which is given below:

Box filter of size 5

1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25
1/25 1/25 1/25 1/25 1/25

Convolved Image (with Box Filter of Size 5)

convolved

Convolved Image (with Box Filter of Size 9)

convolved

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Digital image processing Topics