ColorThreshold 

Overview

ColorThreshold is the color value used by the control to decide whether a pixel should be considered to be black or white. The value should be in the range 0 to 255.

Default value = 128

void STSetParameter(hBarcode, ST_CONTRAST, uint16 *value) ;

void STGetParameter(hBarcode, ST_CONTRAST, uint16 *value) ;

e.g

// Set the ColorThreshold to 140
#include "barcode.h"
uint16 value = 140 ;
STSetParameter(hBarcode, ST_CONTRAST, &value) ;