ILHistogram Interface Reference

This interface provide functionalities of histogram calculation out of image. More...

Inheritance diagram for ILHistogram:

Public Member Functions
void	Build (ILImage *img, ILRegion *region, int binCount, int lowerBound, int upperBound)
void	BuildFromDataVec (LArray< double > dataVec, int binCount, double lowerBound, double upperBound)
void	Draw (HDC hdc, LPVChartDrawFlags drawFlags, int xGridStep, int yGridStep)
double	Item (int index)
void	MeanStdDev (double *meanValue, double *stdDevValue)
void	MinMax (int *minIdx, double *minValue, int *maxIdx, double *maxValue)
Public Member Functions inherited from ILObject
ILObject *	Copy ()
LPVErrorCode	Load (LString filename)
void	Reset ()
LPVErrorCode	Save (LString filename)
BOOL	Valid ()

Detailed Description

This interface provide functionalities of histogram calculation out of image.

Histogram collect count of data in provided image into a set of predefined bins. It is useful in a vision system for analysis and observe the frequency distributions of pixel intensity values, and later do detection or inspection based on it.

To use this interface, you should create a LHistogram object.

Example Code

C++

ILHistogramPtr histOp = LHistogram::Create();
histOp->Build(img, roi, 256, 0, 255);

C#

LHistogram histOp = new LHistogram();
histOp.Build(img, roi, 256, 0, 255);

COM

ILHistogramPtr histOp = LHistogram::Create();
// or, ILHistogramPtr histOp(__uuidof(LHistogram)), for absence of built-in Create functions (before 2.2.0)
histOp->Build(img, roi, 256, 0, 255);

Member Function Documentation

Build()

void Build	(	ILImage *	img,
		ILRegion *	region,
		int	binCount,
		int	lowerBound,
		int	upperBound
	)

Build the histogram with the given image and region.

Parameters

[in]	img	The input image.
[in]	region	Input region. It's optional, could be null.
[in]	binCount	The number of divisions in the histogram. It's recommended to be a factor of the total data range size, say 256 for a grayscale image.
[in]	lowerBound	The lower bound of data, usually it's 0 for a 8bit grayscale image.
[in]	upperBound	The upper bound of data, usually it's 255 for a 8bit grayscale image.

See also

BuildFromDataVec()

BuildFromDataVec()

void BuildFromDataVec	(	LArray< double >	dataVec,
		int	binCount,
		double	lowerBound,
		double	upperBound
	)

Build the histogram with the given data vector.

Parameters

[in]	dataVec	The input data vector, it's a collection of double values.
[in]	binCount	The number of divisions in the histogram.
[in]	lowerBound	The lower bound of data. By default, both the lower and upper bound is set to 0, means we'll use the minimum and maximum value of the inputs as the bounds.
[in]	upperBound	The upper bound of data.

See also

Build()

Draw()

void Draw	(	HDC	hdc,
		LPVChartDrawFlags	drawFlags,
		int	xGridStep,
		int	yGridStep
	)

Draw the histogram as a data chart onto provide device context, using the index as x axis and the value as y axis.

Parameters

[in]	hdc	Handle to the device context of the destination window or bitmap.
[in]	drawFlags	Flags to control which part of a data chart should be drawn, see LPVChartDrawFlags for usage.
[in]	xGridStep	Specify the step of label on x axis, 0 means we'll determine it on the fly according to the score data.
[in]	yGridStep	Specify the step of label on y axis, 0 means we'll determine it on the fly according to the score data. This function is currently not available on Linux / MacOS platform.

Item()

double Item

(

int

index

)

Get value of a specified bin. It represents the count of data in that bin.

Parameters

[in]

index

The index of the bin.

Return values

value

Return the value of the bin.

MeanStdDev()

void MeanStdDev	(	double *	meanValue,
		double *	stdDevValue
	)

Calculate the mean and standard deviation of the histogram.

Parameters

[out]	meanValue	Return the mean value.
[out]	stdDevValue	Return the standard deviation value.

MinMax()

void MinMax	(	int *	minIdx,
		double *	minValue,
		int *	maxIdx,
		double *	maxValue
	)

Find the bin of minimum or maximum value, report the value and bin index. If there's more than one bin with the same value, report the first one.

Parameters

[out]	minIdx	Return the index of the bin of minimum value.
[out]	minValue	Return the minimum value.
[out]	maxIdx	Return the index of the bin of maximum value.
[out]	maxValue	Return the maximum value。