ImageDev

BilateralFilter2d

Applies a two-dimensional edge-preserving smoothing filter.

Access to parameter description

For an introduction to image filters: see Images Filtering.

This algorithm is an edge-preserving smoothing filter. The intensity value at each pixel in an image is replaced by a weighted average of intensity values from nearby pixels. Crucially, the weights depend on the distance in color space from the considered pixel.
It preserves sharp edges by systematically excluding pixels across discontinuities from consideration: $$ O(i,j)=\frac{1}{K(i,j)}\sum_{l=-\frac{n_x}{2}}^{\frac{n_x}{2}} \sum_{m=-\frac{n_y}{2}}^{\frac{n_y}{2}}e^{_\frac{(I(i,j)-I(l,m))^2}{h^2}} I(l,m) $$
Where $h$ is a weighting similarity factor and $K$ is a local normalisation factor given by: $$ K(i,j)=\sum_{l=-\frac{n_x}{2}}^{\frac{n_x}{2}} \sum_{m=-\frac{n_y}{2}}^{\frac{n_y}{2}}e^{_\frac{(I(i,j)-I(l,m))^2}{h^2}} I(l,m) $$
The greater $h$ is, the stronger the blur.

A filter mode parameter allows this algorithm to switch to the SUSAN filter (Smallest Univalue Segment Assimilating Nucleus).
The SUSAN filter reproduces bilateral filter behavior simply by excluding the central pixel of computation. This filter gives better results in the case of impulse noise.

Reference:
C.Tomasi, R.Manduchi. "Bilateral Filtering for Gray and Color Images". Sixth International Conference on Computer Vision (IEEE Cat. No.98CH36271), Bombay, India, pp. 839-846, 1998.

See also

Function Syntax

This function returns the outputImage output parameter. 
// Function prototype.
std::shared_ptr< iolink::ImageView >
bilateralFilter2d( std::shared_ptr< iolink::ImageView > inputImage,
                   int32_t kernelSizeX,
                   int32_t kernelSizeY,
                   double similarity,
                   BilateralFilter2d::FilterMode filterMode,
                   std::shared_ptr< iolink::ImageView > outputImage = NULL );
This function returns the outputImage output parameter. 
// Function prototype.
bilateral_filter_2d( input_image,
                     kernel_size_x = 3,
                     kernel_size_y = 3,
                     similarity = 20,
                     filter_mode = BilateralFilter2d.FilterMode.BILATERAL,
                     output_image = None )
This function returns the outputImage output parameter. 
// Function prototype.
public static IOLink.ImageView
BilateralFilter2d( IOLink.ImageView inputImage,
                   Int32 kernelSizeX = 3,
                   Int32 kernelSizeY = 3,
                   double similarity = 20,
                   BilateralFilter2d.FilterMode filterMode = ImageDev.BilateralFilter2d.FilterMode.BILATERAL,
                   IOLink.ImageView outputImage = null );

Class Syntax

Parameters

Class Name BilateralFilter2d

Parameter Name Description Type Supported Values Default Value
input
inputImage
The input image. Image Binary, Label, Grayscale or Multispectral nullptr
input
kernelSizeX
The horizontal kernel size in pixels (odd value). Int32 [3, 100] 3
input
kernelSizeY
The vertical kernel size in pixels (odd value). Int32 [3, 100] 3
input
similarity
The weighting similarity factor (must be a positive value). Float64 >0 20
input
filterMode
The way to consider the central pixel.
BILATERAL This mode corresponds to the standard bilateral filter (uses the central point).
SUSAN This mode corresponds to the SUSAN filter (does not use the central point).
Enumeration BILATERAL
output
outputImage
The output image. Its dimensions, type, and calibration are forced to the same values as the input. Image nullptr

Object Examples

std::shared_ptr< iolink::ImageView > polystyrene = ioformat::readImage( std::string( IMAGEDEVDATA_IMAGES_FOLDER ) + "polystyrene.tif" );

BilateralFilter2d bilateralFilter2dAlgo;
bilateralFilter2dAlgo.setInputImage( polystyrene );
bilateralFilter2dAlgo.setKernelSizeX( 3 );
bilateralFilter2dAlgo.setKernelSizeY( 3 );
bilateralFilter2dAlgo.setSimilarity( 20.0 );
bilateralFilter2dAlgo.setFilterMode( BilateralFilter2d::FilterMode::BILATERAL );
bilateralFilter2dAlgo.execute();

std::cout << "outputImage:" << bilateralFilter2dAlgo.outputImage()->toString();

polystyrene = ioformat.read_image(imagedev_data.get_image_path("polystyrene.tif"))

bilateral_filter_2d_algo = imagedev.BilateralFilter2d()
bilateral_filter_2d_algo.input_image = polystyrene
bilateral_filter_2d_algo.kernel_size_x = 3
bilateral_filter_2d_algo.kernel_size_y = 3
bilateral_filter_2d_algo.similarity = 20.0
bilateral_filter_2d_algo.filter_mode = imagedev.BilateralFilter2d.BILATERAL
bilateral_filter_2d_algo.execute()

print( "output_image:", str( bilateral_filter_2d_algo.output_image ) );

ImageView polystyrene = ViewIO.ReadImage( @"Data/images/polystyrene.tif" );

BilateralFilter2d bilateralFilter2dAlgo = new BilateralFilter2d
{
    inputImage = polystyrene,
    kernelSizeX = 3,
    kernelSizeY = 3,
    similarity = 20.0,
    filterMode = BilateralFilter2d.FilterMode.BILATERAL
};
bilateralFilter2dAlgo.Execute();

Console.WriteLine( "outputImage:" + bilateralFilter2dAlgo.outputImage.ToString() );

Function Examples

std::shared_ptr< iolink::ImageView > polystyrene = ioformat::readImage( std::string( IMAGEDEVDATA_IMAGES_FOLDER ) + "polystyrene.tif" );

auto result = bilateralFilter2d( polystyrene, 3, 3, 20.0, BilateralFilter2d::FilterMode::BILATERAL );

std::cout << "outputImage:" << result->toString();

polystyrene = ioformat.read_image(imagedev_data.get_image_path("polystyrene.tif"))

result = imagedev.bilateral_filter_2d( polystyrene, 3, 3, 20.0, imagedev.BilateralFilter2d.BILATERAL )

print( "output_image:", str( result ) );

ImageView polystyrene = ViewIO.ReadImage( @"Data/images/polystyrene.tif" );

IOLink.ImageView result = Processing.BilateralFilter2d( polystyrene, 3, 3, 20.0, BilateralFilter2d.FilterMode.BILATERAL );

Console.WriteLine( "outputImage:" + result.ToString() );