mlib_ImageHistogram2

- histogram

Synopsis

cc [ flag... ] file... -lmlib [ library... ]
#include <mlib.h>

mlib_status mlib_ImageHistogram2(mlib_s32 **histo, const mlib_image *img,
     const mlib_s32 *numBins, const mlib_s32 *lowValue,
     const mlib_s32 *highValue, mlib_s32 xStart, mlib_s32 yStart,
     mlib_s32 xPeriod, mlib_s32 yPeriod);

Description

The mlib_ImageHistogram2() function creates a histogram by scanning an image, counting the number of pixels within a given range for each channel of the image, and then generating a histogram.

The image can have 1, 2, 3 or 4 channels. The data type of the image can be MLIB_BYTE, MLIB_SHORT, MLIB_USHORT, or MLIB_INT. The histogram must have the same number of channels as the image has.

One entry of the histogram, or a bin, is used to accumulate the number of pixels within a certain sub-range. The legal pixel range and the number of bins may be controlled separately.

If binWidth is defined as (highValue - lowValue )/numBins then bin i counts pixel values in the following range:

lowValue + i*binWidth ≤ x < lowValue + (i + 1)*binWidth

The set of pixels scanned may furthermore be reduced by specifying xPeriod and yPeriod parameters that specify the sampling rate along each axis.

The set of pixels to be accumulated may be obtained from the following equation:

x = xStart + p*xPeriod;  0 ≤ p < (w - xStart)/xPeriod
y = yStart + q*yPeriod;  0 ≤ q < (h - yStart)/yPeriod

It is the user's responsibility to clear the histogram table before this function is called and to ensure that the histogram table supplied is suitable for the source image and the parameters. Otherwise, the result of this function is undefined.

The range from lowValue[k] to (highValue[k] - 1) must be a valid subrange of the image type range.

Parameters

The function takes the following arguments:

histo

Pointer to histogram. The format of the histogram is histo[channel][index]. The index values for channel i can be 0, 1, ..., numBins[i]-1.

img

Pointer to source image.

numBins

The number of bins for each channel of the image.

lowValue

The lowest pixel value checked for each channel.

highValue

The highest pixel value checked for each channel. When counting the pixel values, highValue is not included.

xStart

The initial X sample coordinate.

yStart

The initial Y sample coordinate.

xPeriod

The X sampling rate. xPeriod ≥ 1.

yPeriod

The Y sampling rate. yPeriod ≥ 1.

Return Values

The function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

mlib_ImageHistogram(3MLIB), attributes(5)