ImageDev

Pruning2d

Point detector removing spurs from a two-dimensional binary image.

Access to parameter description

For an introduction: This algorithm prunes the result of a skeletonization. It removes all object pixels having only one neighbor.
It can be applied either specifying a number of iterations or until convergence.
This filter can be used for removing terminal branches from a skeleton, also known as spurs.

The skeleton is very sensitive to small distortions on the edges of the objects, generating artifacts. The pruning algorithm eliminates these artifacts by thinning with the following structuring element until convergence or for a predefined number of iterations.

The skeleton is first detected, and then this algorithm performs a thinning transform with the following configuration and its 7 associated rotations: $$ \begin{array}{ccc} 0 & 0 & \times\\ 0 & 1 & 0\\ 0 & 0 & 0 \end{array} $$ Where $\times$ means "don't care".

It is generally tedious to determine the number of iterations for the pruning and thinning until convergence removes all the skeletons except loops and branches intersecting the frame of the image in permissive mode.
The strict mode stops when an intersection or a right angle is encountered.

See also

Function Syntax

This function returns outputBinaryImage. 
// Function prototype
std::shared_ptr< iolink::ImageView >
pruning2d( std::shared_ptr< iolink::ImageView > inputBinaryImage,
           Pruning2d::PruningMode pruningMode,
           int32_t numberOfIterations,
           std::shared_ptr< iolink::ImageView > outputBinaryImage = NULL );
This function returns outputBinaryImage. 
// Function prototype.
pruning_2d( input_binary_image,
            pruning_mode = Pruning2d.PruningMode.RIGOROUS,
            number_of_iterations = 1,
            output_binary_image = None )
This function returns outputBinaryImage. 
// Function prototype.
public static IOLink.ImageView
Pruning2d( IOLink.ImageView inputBinaryImage,
           Pruning2d.PruningMode pruningMode = ImageDev.Pruning2d.PruningMode.RIGOROUS,
           Int32 numberOfIterations = 1,
           IOLink.ImageView outputBinaryImage = null );

Class Syntax

Parameters

Parameter Name Description Type Supported Values Default Value
input
inputBinaryImage
The binary input image. Image Binary nullptr
input
pruningMode
The mode for removing end points.
RIGOROUS Each iteration removes only the end points having one neighbor. Using this mode, the pruning stops when an intersection or a right angle is encountered.
PERMISSIVE A skeletonization is reapplied between two iterations. Using this mode, only the closed-loops are kept.
Enumeration RIGOROUS
input
numberOfIterations
The number of iterations. If equal to 0, the algorithm is run until convergence. Int32 >=0 1
output
outputBinaryImage
The binary output image. Its size and type are forced to the same values as the input. Image nullptr
Parameter Name Description Type Supported Values Default Value
input
input_binary_image
The binary input image. image Binary None
input
pruning_mode
The mode for removing end points.
RIGOROUS Each iteration removes only the end points having one neighbor. Using this mode, the pruning stops when an intersection or a right angle is encountered.
PERMISSIVE A skeletonization is reapplied between two iterations. Using this mode, only the closed-loops are kept.
enumeration RIGOROUS
input
number_of_iterations
The number of iterations. If equal to 0, the algorithm is run until convergence. int32 >=0 1
output
output_binary_image
The binary output image. Its size and type are forced to the same values as the input. image None
Parameter Name Description Type Supported Values Default Value
input
inputBinaryImage
The binary input image. Image Binary null
input
pruningMode
The mode for removing end points.
RIGOROUS Each iteration removes only the end points having one neighbor. Using this mode, the pruning stops when an intersection or a right angle is encountered.
PERMISSIVE A skeletonization is reapplied between two iterations. Using this mode, only the closed-loops are kept.
Enumeration RIGOROUS
input
numberOfIterations
The number of iterations. If equal to 0, the algorithm is run until convergence. Int32 >=0 1
output
outputBinaryImage
The binary output image. Its size and type are forced to the same values as the input. Image null

Object Examples

auto polystyrene_sep = readVipImage( std::string( IMAGEDEVDATA_IMAGES_FOLDER ) + "polystyrene_sep.vip" );

Pruning2d pruning2dAlgo;
pruning2dAlgo.setInputBinaryImage( polystyrene_sep );
pruning2dAlgo.setPruningMode( Pruning2d::PruningMode::RIGOROUS );
pruning2dAlgo.setNumberOfIterations( 1 );
pruning2dAlgo.execute();

std::cout << "outputBinaryImage:" << pruning2dAlgo.outputBinaryImage()->toString();

polystyrene_sep = imagedev.read_vip_image(imagedev_data.get_image_path("polystyrene_sep.vip"))

pruning_2d_algo = imagedev.Pruning2d()
pruning_2d_algo.input_binary_image = polystyrene_sep
pruning_2d_algo.pruning_mode = imagedev.Pruning2d.RIGOROUS
pruning_2d_algo.number_of_iterations = 1
pruning_2d_algo.execute()

print( "output_binary_image:", str( pruning_2d_algo.output_binary_image ) )

ImageView polystyrene_sep = Data.ReadVipImage( @"Data/images/polystyrene_sep.vip" );

Pruning2d pruning2dAlgo = new Pruning2d
{
    inputBinaryImage = polystyrene_sep,
    pruningMode = Pruning2d.PruningMode.RIGOROUS,
    numberOfIterations = 1
};
pruning2dAlgo.Execute();

Console.WriteLine( "outputBinaryImage:" + pruning2dAlgo.outputBinaryImage.ToString() );

Function Examples

auto polystyrene_sep = readVipImage( std::string( IMAGEDEVDATA_IMAGES_FOLDER ) + "polystyrene_sep.vip" );

auto result = pruning2d( polystyrene_sep, Pruning2d::PruningMode::RIGOROUS, 1 );

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

polystyrene_sep = imagedev.read_vip_image(imagedev_data.get_image_path("polystyrene_sep.vip"))

result = imagedev.pruning_2d( polystyrene_sep, imagedev.Pruning2d.RIGOROUS, 1 )

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

ImageView polystyrene_sep = Data.ReadVipImage( @"Data/images/polystyrene_sep.vip" );

IOLink.ImageView result = Processing.Pruning2d( polystyrene_sep, Pruning2d.PruningMode.RIGOROUS, 1 );

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