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As it turns out, this is perhaps the simplest of the three overridden paint methods. The method begins in Listing 27 where the getColorPalette method is called to get a reference to the color palette discussed above.
Then a pair of nested for loops is set up to process every elevation value on the 3D surface.
| Listing 27. Beginning of overridden paint method. |
|---|
public void paint(Graphics g){
Color[]colorPalette = getColorPalette();
for(int row = 0;row<dataHeight;row++){
for(int col = 0;col<dataWidth;col++){
int quantizedData = (int)(Math.round(data[row][col]*(
colorPalette.length-1)/255)); |
The code in Listing 27 quantizes the elevation levels into a set of integer values ranging from 0 to one less than the number of elements in the colorpalette. As written, this redefines the normalized elevation values as extending from 0 to 22, instead of from 0 to 255.
(If you change the length of the color palette, the number of ranges will change accordingly.)
The code in Listing 28 uses the quantized elevation value to index into the color palette and retrieve a reference to a Color object. This reference is passed to the setColor method setting the current plotting color to the color represented by that index value.
| Listing 28. Set the color value. |
|---|
g.setColor(colorPalette[quantizedData]); |
Having set the current plotting color, as in the other two cases discussed earlier, the method goes on to paint a square of pixels in that color at thecorrect location. Then it draws the optional axes if specified. The code to accomplish these operations is the same as code discussed previously, so I won'trepeat that discussion here. You can view the code in Listing 29 near the end of the module.
This inner class is used to construct a color scale that matches the color algorithm used in the class named CanvasType2surface . Except for the difference in the overridden paint method, this class is essentially the same as the other two classes used to construct color scaleobjects. Therefore, I won't repeat that discussion.
You can view the class in its entirety in Listing 29 near the end of the module. You can view the graphic output produced by this class in thecalibration scale for the image at the rightmost end of Figure 1 .
I encourage you to copy, compile, and run the program that you will find in Listing 29 . Modify the program and experiment with it in order to learn as much as you can about the use of Java for displaying 3D data.
A better color scheme
See if you can come up with a better color scheme than the color schemes that I used in my version of the program. For example, you might add new colors tothe color palette used for the Color Contour plot. That will be very easy to do. All you need to do is add them to the array.
(The hard part will be to identify new colors that are visually separable from the colors that are already being used.)
You might also add new colors to the color algorithm for the Color Shift plot. This will be somewhat more difficult in that additional coding will berequired to incorporate those new colors.
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