IlvConvolutionFilter Class Reference

Convolution filter. More...

#include <ilviews/bitmaps/filters/convolve.h>

Inheritance diagram for IlvConvolutionFilter:

List of all members.

Public Member Functions
	IlvConvolutionFilter (IlvBitmapDataKernel *kernel=0, IlFloat divisor=0, IlFloat bias=0.0)
	Constructor.
	~IlvConvolutionFilter ()
	Destructor.
IlvBitmapData *	apply (IlUInt count=0, const IlvBitmapData **inputs=0)
	Applies the convolution to the given image.
IlFloat	getBias () const
	Returns the bias.
IlFloat	getDivisor () const
	Returns the divisor.
IlvConvolutionFilter::EdgeMode	getEdgeMode () const
	Returns the edge mode.
IlvBitmapDataKernel *	getKernel () const
	Returns the kernel.
void	setBias (IlFloat bias)
	Sets the bias.
void	setDivisor (IlFloat divisor)
	Sets the divisor.
void	setEdgeMode (IlvConvolutionFilter::EdgeMode mode)
	Sets the edge mode.
void	setKernel (IlvBitmapDataKernel *kernel)
	Sets the kernel.

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Detailed Description

Convolution filter.

Library: ilvbmpflt

This bitmap filter lets you apply a matrix convolution to an image. A convolution combines pixels in the input image with neighboring pixels to produce a resulting image. A wide variety of imaging operations can be achieved through convolutions, including blurring, edge detection, sharpening, embossing, and beveling. A matrix convolution is based on an n-by-m matrix (the convolution kernel) that describes how a given pixel value in the input image is combined width its neighboring pixel values to produce a resulting pixel value.

To illustrate, suppose you have an input image that is 5 by 5 pixels, whose color values are as follows:

   0   20   40  235  235
 100  120  140  235  235
 200  220  240  235  255
 225  225  255  255  255
 225  225  255  255  255
 

and you define a 3-by-3 convolution kernel as follows:

  1  2  3
  4  5  6
  7  8  9
 

Let's focus on the pixel at the second row and second column of the source image (source pixel value is 120). The resulting pixel value will be:

 (1 * 0 + 2 * 20 + 3 * 40 + 
 4 * 100 + 5 * 120 + 6 * 140 +
 7 * 200 + 8 * 220 + 9 * 240) / (1 + 2 + 3 +4 + 5 + 6 + 7 + 8 + 9)
 

By default the divisor is the sum of the kernel coefficients but can be specified. A bias value can be added after computing the value. An edge mode can be specified for border values. The edge mode can be one of:

• IlvConvolutionFilter::Duplicate: The border pixels are duplicated.
• IlvConvolutionFilter::Wrap: The border pixels are extended using the opposite edge.
• IlvConvolutionFilter::None: The border pixels are extended with 0 values.

See also:

IlvRGBBitmapData, IlvBitmapFilter, IlvBitmapKernel

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Constructor & Destructor Documentation

IlvConvolutionFilter::IlvConvolutionFilter	(	IlvBitmapDataKernel *	kernel = 0,
		IlFloat	divisor = 0,
		IlFloat	bias = 0.0
	)

Constructor.

Initializes a new instance of the class IlvConvolutionFilter. The default operator is a 3x3 identity kernel.

IlvConvolutionFilter::~IlvConvolutionFilter

(

)

Destructor.

The destructor releases all the memory used by the instance.

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Member Function Documentation

IlFloat IlvConvolutionFilter::getBias

(

)

const

Returns the bias.

Returns:

The bias.

IlFloat IlvConvolutionFilter::getDivisor

(

)

const

Returns the divisor.

Returns:

The divisor.

IlvConvolutionFilter::EdgeMode IlvConvolutionFilter::getEdgeMode

(

)

const

Returns the edge mode.

Returns:

The edge mode.

IlvBitmapDataKernel* IlvConvolutionFilter::getKernel

(

)

const

Returns the kernel.

Returns:

The kernel.

void IlvConvolutionFilter::setBias

(

IlFloat

bias

)

Sets the bias.

Parameters:

bias

The new bias.

void IlvConvolutionFilter::setDivisor

(

IlFloat

divisor

)

Sets the divisor.

If the divisor is 0 then the sum of the kernel coefficients is used. If this coefficient is 0 then the divisor is 1.0.

Parameters:

divisor

The new divisor.

void IlvConvolutionFilter::setEdgeMode

(

IlvConvolutionFilter::EdgeMode

mode

)

Sets the edge mode.

Parameters:

mode

The new edge mode.

void IlvConvolutionFilter::setKernel

(

IlvBitmapDataKernel *

kernel

)

Sets the kernel.

Parameters:

kernel

The new kernel.