mlib_ImageExtremaLocations

, mlib_ImageExtremaLocations_Fp

- image extrema and their locations

Synopsis

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

mlib_status mlib_ImageExtremaLocations( mlib_s32 *min, mlib_s32 *max,
     const mlib_image *img, mlib_s32 xStart, mlib_s32 yStart,
     mlib_s32 xPeriod, mlib_s32 yPeriod, mlib_s32 saveLocations,
     mlib_s32 maxRuns, mlib_s32 *minCounts, mlib_s32 *maxCounts,
     mlib_s32 **minLocations, mlib_s32 **maxLocations, mlib_s32 len);

mlib_status mlib_ImageExtremaLocations_Fp( mlib_d64 *min, mlib_d64 *max,
     const mlib_image *img, mlib_s32 xStart, mlib_s32 yStart,
     mlib_s32 xPeriod, mlib_s32 yPeriod, mlib_s32 saveLocations,
     mlib_s32 maxRuns, mlib_s32 *minCounts, mlib_s32 *maxCounts,
     mlib_s32 **minLocations, mlib_s32 **maxLocations, mlib_s32 len);

Description

Each of the functions finds the image-wise minimum and maximum pixel values for each channel, and optionally, their locations.

Each of the functions scans an image, finds the minimum and maximum pixel values for each channel, and finds the locations of those pixels with the minimum or maximum values.

The user provides initial minimum/maximum values through the arguments min and max. This function will update them based on findings.

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 scanned 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

The locations of the minimum/maximum, if asked, are recorded in a format of run-length coding. Each run-length code, or simply called a run, has a format of (xStart, yStart, length). Here length is defined on the low-resolution image (with downsampling factors of 1/xPeriod, 1/yPeriod) and does not cross rows. So the run-length code (xStart, yStart, length) means that the pixels at (xStart, yStart), (xStart + xPeriod, yStart), ..., (xStart + (length - 1)*xPeriod, yStart) of the original image have a value of the minimum/maximum.

The buffers for minLocations and maxLocations are organized in the following format for each channel i:

minLocations[i][0] = xStart0;  // the 1st run
minLocations[i][1] = yStart0;
minLocations[i][2] = length0;
minLocations[i][3] = xStart1;  // the 2nd run
minLocations[i][4] = yStart1;
minLocations[i][5] = length1;
            ......             // more runs
minLocations[i][len-1] = ...;

It is the user's responsibility to allocate enough memory for the buffers for minLocations and maxLocations. This function may return MLIB_OUTOFRANGE, if any of the buffers is not big enough.

Parameters

The function takes the following arguments:

min

Pointer to the minimum values.

max

Pointer to the maximum values.

img

Pointer to the input image.

xStart

Initial X sample coordinate.

yStart

Initial Y sample coordinate.

xPeriod

X sampling rate. xPeriod ≥ 1.

yPeriod

Y sampling rate. yPeriod ≥ 1.

saveLocations

If true (i.e., saveLocations != 0), find the extrema locations; otherwise only find the extrema.

maxRuns

Number of runs of the minimum/maximum the caller expects for each channel. maxRuns ≥ 1. If it is MLIB_S32_MAX, all the minimum/maximum locations should be recorded.

minCounts

Pointer to the numbers of runs of the minimum recorded in minLocations.

maxCounts

Pointer to the numbers of runs of the maximum recorded in maxLocations.

minLocations

Pointer to the minimum locations in a format of run-length coding.

maxLocations

Pointer to the maximum locations in a format of run-length coding.

len

Length of the buffers for the minimum/maximum locations in each channel.

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_ImageExtrema2(3MLIB), mlib_ImageMaximum(3MLIB), mlib_ImageMaximum_Fp(3MLIB), mlib_ImageMinimum(3MLIB), mlib_ImageMinimum_Fp(3MLIB), attributes(5)