ImageDev

ZeroCrossings2d

Thresholds pixels where the sign of a Laplacian image changes.

Access to parameter description

For an introduction: Zero-crossings are points where the Laplacian switches from positive to negative values, and vice versa.

A simple zero-crossing detection is obtained by thresholding the Laplacian to retain positive intensities, then detecting the boundaries of the binary image, as shown in Figure 1. Such zero-crossing points are not precisely located.

<b> Figure 1.</b> Thresholding a Laplacian to determine the zero-crossings
Figure 1. Thresholding a Laplacian to determine the zero-crossings

Zero-crossing is even better to mark a point if the Laplacian changes its sign in its 3x3 neighbourhood, and if the Laplacian magnitude is smaller than all magnitudes in that neighbourhood, as shown in Figure 2.

<b> Figure 2.</b> Zero-crossing a Laplacian
Figure 2. Zero-crossing a Laplacian

Compared to thresholding of a gradient, zero-crossings have the advantage of producing closed curves of 1 pixel thickness. This is most interesting when precise object boundary detection is the goal.
See also

Function Syntax

This function returns outputBinaryImage. 
// Function prototype
std::shared_ptr< iolink::ImageView >
zeroCrossings2d( std::shared_ptr< iolink::ImageView > inputImage, std::shared_ptr< iolink::ImageView > outputBinaryImage = NULL );
This function returns outputBinaryImage. 
// Function prototype.
zero_crossings_2d( input_image, output_binary_image = None )
This function returns outputBinaryImage. 
// Function prototype.
public static IOLink.ImageView
ZeroCrossings2d( IOLink.ImageView inputImage, IOLink.ImageView outputBinaryImage = null );

Class Syntax

Parameters

Class Name ZeroCrossings2d

Parameter Name Description Type Supported Values Default Value
input
inputImage
The input image. Image Binary, Label, Grayscale or Multispectral nullptr
output
outputBinaryImage
The binary output image. Image nullptr

Object Examples

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

ZeroCrossings2d zeroCrossings2dAlgo;
zeroCrossings2dAlgo.setInputImage( polystyrene );
zeroCrossings2dAlgo.execute();

std::cout << "outputBinaryImage:" << zeroCrossings2dAlgo.outputBinaryImage()->toString();

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

zero_crossings_2d_algo = imagedev.ZeroCrossings2d()
zero_crossings_2d_algo.input_image = polystyrene
zero_crossings_2d_algo.execute()

print( "output_binary_image:", str( zero_crossings_2d_algo.output_binary_image ) )

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

ZeroCrossings2d zeroCrossings2dAlgo = new ZeroCrossings2d
{
    inputImage = polystyrene
};
zeroCrossings2dAlgo.Execute();

Console.WriteLine( "outputBinaryImage:" + zeroCrossings2dAlgo.outputBinaryImage.ToString() );

Function Examples

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

auto result = zeroCrossings2d( polystyrene );

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

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

result = imagedev.zero_crossings_2d( polystyrene )

print( "output_binary_image:", str( result ) )

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

IOLink.ImageView result = Processing.ZeroCrossings2d( polystyrene );

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