Interface BilevelImage

All Superinterfaces:
GrayImage, GrayIntegerImage, IntegerImage, PixelImage
All Known Implementing Classes:
MemoryBilevelImage

public interface BilevelImage extends GrayIntegerImage
An interface for bilevel pixel image data classes. Each pixel in a bilevel image can have two possible values, BLACK and WHITE. Those two constants are guaranteed to be 0 and 1, although you should not make any assumptions about what value any of the two constants has. This is the type of image used for faxes. Black and white photos are usually stored as grayscale images.

Apart from implementing PixelImage - like all image data classes in JIU - this interface is also an IntegerImage (each sample is either 0 or 1) and a GrayImage (black and white are both grayscale values). The combination of IntegerImage and GrayImage is GrayIntegerImage, which is the direct superinterface of this interface.

Packed bytes

There are methods to get and put packed bytes in this interface. A packed byte is a byte value that stores eight horizontally neighbored bilevel pixels in it (pixel and sample can be used interchangeably in the context of bilevel images because there is only one sample per pixel). The most significant bit of such a packed bit is defined to be the leftmost of the eight pixels, the second-most significant bit is the pixel to the right of that leftmost pixel, and so on. The least significant bit is the rightmost pixel. If a bit is set, the corresponing pixel value is supposed to be white, otherwise black.

Usage examples

Here are some code examples that demonstrate how to access image data with this class.
 BilevelImage image = new MemoryBilevelImage(2000, 500);
 // now set all pixels in the first row to white
 for (int x = 0; x < image.getWidth(); x++)
 {
   image.putWhite(x, 0);
 }
 // put vertical stripes on the rest
 for (int y = 1; y < image.getHeight(); y++)
 {
   for (int x = 0; x < image.getWidth(); x++)
   {
     int sample;
     if ((x % 2) == 0)
     {
       sample = BilevelImage.BLACK;
     }
     else
     {
       sample = BilevelImage.WHITE;
     }
     image.putSample(x, y, sample);
   }
 }
 
Author:
Marco Schmidt
  • Field Details

    • BLACK

      static final int BLACK
      The value for a black pixel. To be used with all methods that require int arguments for sample values. You can rely on this value being either 0 or 1 (that way you can safely store it in a byte or short).
      See Also:
    • WHITE

      static final int WHITE
      The value for a white pixel. To be used with all methods that require int arguments for sample values. You can rely on this value being either 0 or 1 (that way you can safely store it in a byte or short).
      See Also:
  • Method Details

    • getPackedBytes

      void getPackedBytes(int x, int y, int numSamples, byte[] dest, int destOffset, int destBitOffset)
      Sets a number of samples in the argument array from this image.
      Parameters:
      x - horizontal position of first sample of this image to read
      y - vertical position of samples to be read from this image
      numSamples - number of samples to be set
      dest - array with packed pixels to which samples are copied
      destOffset - index into dest array of the first byte value to write sample values to
      destBitOffset - index of first bit of dest[destOffset] to write a sample to (0 is leftmost, 1 is second-leftmost up to 7, which is the rightmost)
    • putPackedBytes

      void putPackedBytes(int x, int y, int numSamples, byte[] src, int srcOffset, int srcBitOffset)
      Sets a number of samples in the image from the argument array data.
      Parameters:
      x - horizontal position of first sample to be set
      y - vertical position of samples to be set
      numSamples - number of samples to be set
      src - array with packed pixels to be set
      srcOffset - index into src array of the first byte value to read sample values from
      srcBitOffset - index of first bit of src[srcOffset] to read a sample from (0 is leftmost, 1 is second-leftmost up to 7, which is the rightmost)