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Accessing Grayscale Images Example

Accessing Grayscale Images Example

This example creates a a grayscale ramp image within a Java class, which is contained in a file named GreyBandsImage.java. IDL then accesses this data through the ShowGreyImage routine, which is in the showgreyimage.pro file.

Note: These files are located in the resource/bridges/import/java/examples directory of the IDL distribution. Run this example procedure by entering window by entering .EDIT showgreyimage.pro.

The GreyBandsImage.java file contains the following text for creating a grayscale image in Java:

import java.awt.*;
import java.awt.image.*;
public class GreyBandsImage extends BufferedImage
  // Members
  private int m_height;
  private int m_width;
  // ctor
  public GreyBandsImage()
  super(100, 100, BufferedImage.TYPE_INT_ARGB);
  m_height = 100;
  m_width = 100;
  // private method to generate the image
  private void generateImage()
  Color c;
  int width	= getWidth();
  int height = getHeight();
  WritableRaster raster = getRaster();
  ColorModel model = getColorModel();
  int nBands = width/BAND_PIXEL_WIDTH;
  int greyDelta = 255 / nBands;
  for (int i=0 ; i < nBands; i++)
  c = new Color(i*greyDelta, i*greyDelta, i*greyDelta);
  int argb = c.getRGB();
  Object colorData = model.getDataElements(argb, null);
  for (int j=0; j < height; j++)
  for (int k=0; k < BAND_PIXEL_WIDTH; k++)
  raster.setDataElements(j, (i*5)+k, colorData);
  // mutators
  public int[] getRawData()
  Raster oRaster = getRaster();
  Rectangle oBounds = oRaster.getBounds();
  int[] data = new int[m_height * m_width * 4];
  data = oRaster.getPixels(0,0,100,100, data);
  return data;
  public int getH()
  return m_height;
  public int getW()
  return m_width;

The showgreyimage.pro file contains the following text for accessing the grayscale image within IDL:

PRO ShowGreyImage
  ; Construct the GreyBandImage in Java. This is a sub-class of BufferedImage.
  ; It is actually a 4 band image that happens to display bands in greyscale.
  ; It is 100x100 pixels.
  oGrey = OBJ_NEW('IDLjavaObject$GreyBandsImage', 'GreyBandsImage')
  ; Get the 4 byte pixel values.
  data = oGrey -> GetRawData()
  ; Get the height and width.
  h = oGrey -> GetH()
  w = oGrey -> GetW()
  ; Display the graphic in an IDL window
  WINDOW, 0, XSIZE = 100, YSIZE = 100
  TV, REBIN(data, h, w)
  ; Cleanup

After saving and compiling the above files (GreyBandsImage.java in Java and showgreyimage.pro in IDL), you can run the ShowGreyImage routine in IDL. The routine should produce the following image:

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