How to use

histogram

method

in

boofcv.alg.misc.GImageStatistics

/**
 * <p>
 * Computes the variance based threshold using a modified Otsu method from an input image. Internally it uses
 * {@link #computeOtsu2(int[], int, int)} and {@link boofcv.alg.misc.GImageStatistics#histogram(ImageGray, double, int[])}
 * </p>
 *
 * @param input Input gray-scale image
 * @param minValue The minimum value of a pixel in the image.  (inclusive)
 * @param maxValue The maximum value of a pixel in the image.  (inclusive)
 * @return Selected threshold.
 */
public static int computeOtsu2(ImageGray input , int minValue , int maxValue ) {
  int range = 1+maxValue - minValue;
  int histogram[] = new int[ range ];
  GImageStatistics.histogram(input,minValue,histogram);
  // Total number of pixels
  int total = input.width*input.height;
  return computeOtsu2(histogram,range,total)+minValue;
}

/**
 * <p>
 * Computes the variance based threshold using Otsu's method from an input image. Internally it uses
 * {@link #computeOtsu(int[], int, int)} and {@link boofcv.alg.misc.GImageStatistics#histogram(ImageGray, double, int[])}
 * </p>
 *
 * @param input Input gray-scale image
 * @param minValue The minimum value of a pixel in the image.  (inclusive)
 * @param maxValue The maximum value of a pixel in the image.  (inclusive)
 * @return Selected threshold.
 */
public static double computeOtsu(ImageGray input , double minValue , double maxValue ) {
  int range = (int)(1+maxValue - minValue);
  int histogram[] = new int[ range ];
  GImageStatistics.histogram(input,minValue,histogram);
  // Total number of pixels
  int total = input.width*input.height;
  return computeOtsu(histogram,range,total)+minValue;
}

/**
 * <p>
 * Computes a threshold which maximizes the entropy between the foreground and background regions.  See
 * {@link #computeEntropy(int[], int, int)} for more details.
 * </p>
 *
 * @see boofcv.alg.misc.GImageStatistics#histogram(ImageGray, double, int[])
 *
 * @param input Input gray-scale image
 * @param minValue The minimum value of a pixel in the image.  (inclusive)
 * @param maxValue The maximum value of a pixel in the image.  (inclusive)
 * @return Selected threshold.
 */
public static double computeEntropy(ImageGray input , double minValue , double maxValue ) {
  int range = (int)(1 + maxValue - minValue);
  int histogram[] = new int[ range ];
  GImageStatistics.histogram(input,minValue,histogram);
  // Total number of pixels
  int total = input.width*input.height;
  return computeEntropy(histogram, range, total)+minValue;
}