Problem extracting red, green and blue from ColorModel

Question

Hi everyone,
I'm attempting to write a piece of code to extract the red, green and blue components from an image using the ColorModel class. When I attempt to run my code below, I get the following error: Exception in thread "main" java.lang.IllegalArgumentException: More than one component per pixel. Does anyone know how to extract an integer representation of the red in a pixel in order to solve the problem? Here's the code snippet:
public void getRGBValues()
          String imageFilename = new String("C:\\Documents and Settings\\David\\My Documents\\My Pictures\\blue hills1.jpg");
         PlanarImage image = JAI.create("fileload", imageFilename);
         //Get the color model for that particular image
         ColorModel imageColorModel = image.getColorModel();
         //ints to store the appropriate values for each colour component
         int totalRed = 0;
         int totalGreen = 0;
         int totalBlue = 0;
         int averageRed = 0;
         int averageGreen = 0;
         int averageBlue = 0;
         int pixelNumber = 0;
         int pixelCount = 0;
         //Loop to extract the colour values out of each pixel in an image passed into the class
         for(int i = 0; i < image.getWidth(); i++)
              for (int j = 0; j < image.getHeight(); j++)
                   totalRed += imageColorModel.getRed(pixelNumber);
                   totalGreen += imageColorModel.getGreen(pixelNumber);
                   totalBlue += imageColorModel.getBlue(pixelNumber);
                   pixelCount++;
                   pixelNumber++;
              pixelCount++;
              pixelNumber++;
         averageRed = Math.round(totalRed / pixelCount);
          averageGreen = Math.round(totalGreen / pixelCount);
          averageBlue = Math.round(totalBlue / pixelCount);
          System.out.println("Average red is " + averageRed);
          System.out.println("Average green is " + averageGreen);
          System.out.println("Average blue is " + averageBlue);
}

Answer 1

You are misunderstanding the ColorModel methods. The color model can translate between colors and pixels, but it doesn't know or hold pixel data.
I don't know the JAI, but if you use J2SE classes like BufferedImage, this is easy to do:
BufferedImage im = ImageIO.read(input);
int argb = im.getRGB(x, y);
int r = 0xff & (argb>>16);
int g = 0xff & (argb >>8);
int b = 0xff & argb;