Class OrderedDither

All Implemented Interfaces:
RGBIndex

public class OrderedDither extends ImageToImageOperation implements RGBIndex
This operation reduces the color depth of RGB truecolor images and grayscale images by applying ordered dithering. A relatively nice output image (for a human observer) will be created at the cost of introducing noise into the output image. The algorithm is relatively fast, but its quality is usually inferior to what can be reached by using ErrorDiffusionDithering or similar other methods.

Supported conversions

  • Grayscale to bilevel maps GrayIntegerImage objects to BilevelImage objects.
  • Grayscale to grayscale maps GrayIntegerImage objects to other GrayIntegerImage objects. Right now, only Gray8Image objects are supported. After reducing the number of bits, each sample is immediately scaled back to 8 bits per pixel in order to fit into another Gray8Image object.
  • Truecolor to paletted maps RGBIntegerImage objects to Paletted8Image objects; the sum of the output bits must not be larger than 8

Usage example

The following code snippet demonstrates how to create a paletted image with 256 colors, using three bits for red and green and two bits for blue, from an RGB truecolor image.
 OrderedDither od = new OrderedDither();
 od.setRgbBits(3, 3, 2);
 od.setInputImage(image);
 od.process();
 Paletted8Image ditheredImage = (Paletted8Image)od.getOutputImage();
 
Author:
Marco Schmidt
  • Field Details

    • values

      private int[] values
    • valueWidth

      private int valueWidth
    • valueHeight

      private int valueHeight
    • grayBits

      private int grayBits
    • redBits

      private int redBits
    • greenBits

      private int greenBits
    • blueBits

      private int blueBits
  • Constructor Details

    • OrderedDither

      public OrderedDither()
  • Method Details

    • process

      private void process(Gray8Image in, Gray8Image out)
    • process

      private void process(Gray8Image in, BilevelImage out)
    • process

      private void process(RGB24Image in, Paletted8Image out)
    • process

      private void process(RGB24Image in, RGB24Image out)
    • process

      public void process() throws MissingParameterException, WrongParameterException
      Description copied from class: Operation
      This method does the actual work of the operation. It must be called after all parameters have been given to the operation object.
      Overrides:
      process in class Operation
      Throws:
      MissingParameterException - if any mandatory parameter was not given to the operation
      WrongParameterException - if at least one of the input parameters was not initialized appropriately (values out of the valid interval, etc.)
    • setOutputBits

      public void setOutputBits(int bits)
    • setRgbBits

      public void setRgbBits(int red, int green, int blue)
      Sets the number of bits to be used for each RGB component in the output image. Each argument must be one or larger. The values defined by this method are only used if the input image implements RGBIntegerImage. Later, in process(net.sourceforge.jiu.data.Gray8Image, net.sourceforge.jiu.data.Gray8Image), these values are checked against the actual number of bits per component in the input image. If any of the arguments of this method is equal to or larger than those actual bits per channel values, a WrongParameterException will then be thrown. Right now, there is no way how this can be checked, because the input image may not have been defined yet.
      Parameters:
      red - number of bits for the red channel in the output image
      green - number of bits for the green channel in the output image
      blue - number of bits for the blue channel in the output image
      Throws:
      IllegalArgumentException - if at least one argument is smaller than 1
    • setStandardThresholdValues

      public void setStandardThresholdValues()
      Calls setThresholdValues(int[], int, int) with a 16 x 16 matrix.
    • setThresholdValues

      public void setThresholdValues(int[] values, int valueWidth, int valueHeight)
      Defines a matrix of threshold values that will be used for grayscale dithering.
      Parameters:
      values - the int values to use for comparing
      valueWidth -
      valueHeight -