The C interface for histogram equalization. More...

afError	af_histequalize_S (float d_out, unsigned length, const float d_data, unsigned nbins, const float *d_bins)
	Equalize a given vector or matrix based on a given histogram. More...

Detailed Description

The C interface for histogram equalization.

A histogram is a representation of the distribution of data in an image. This representation is essentially a graph consisting of the data range or domain on one axis and frequency of occurence on the other axis. All the data in the domain is counted in the appropriate bin. The total number of elements belonging to each bin is known as the bin's frequency.

The regular histogram function creates bins of equal size between the minimum and maximum of the input data (calculated internally). The histogram min-max function takes input parameters minimum and maximum, and divides the bins into equal sizes within the range specified by min and max parameters. All values less than min in the data range are placed in the first (min) bin and all values greater than max will be placed in the last (max) bin.

// Create a histogram using 256 bins
array hist_out = histogram(hist_in, 256);
// Histogram with explicit min/max
// generate sample input data
// generates an array with 50 elements from -25 to 24.
array hist_in = seq(-25, 24)
// Create histogram using 10 bins,with bins scaled from 1 to 10
// bin[0] gets -inf to 1
// bin[9] gets   10 to inf
array hist_out = histogram(img_in, 10, 0, 10);
// hist_out will be [26, 1, 1, 1, 1, 1, 1, 1, 1, 16]

Data normalization via histogram equalization

// img_in and img_out are single channel images
array ihist = histogram(img_in, 256);
array img_out = histequal(img_in, ihist);

Function Documentation

afError af_histequalize_S	(	float *	d_out,
		unsigned	length,
		const float *	d_data,
		unsigned	nbins,
		const float *	d_bins
	)

Equalize a given vector or matrix based on a given histogram.

Parameters

[out]	d_out	Device-side equalized data
[in]	length	Length of input vector `d_data` (M*N for matrix)
[in]	d_data	Device-side vector or matrix of elements to equalize
[in]	nbins	Number of bins in `h_bins`
[in]	d_bins	Device-side bins

Note: Currently only vector input histograms are supported; Only the range [0-255] (256 bins) is supported.Single-precision histogram normalization.