import java.awt.image.*;

// This class implements a gray color model
// scheme based on another color model. It acts
// like a gray filter. To compute the amount of
// gray for a pixel, it takes the max of the red,
// green, and blue components and uses that value
// for all three color components.

public class GrayModel extends ColorModel
{
   ColorModel originalModel;

   public GrayModel(ColorModel originalModel)
   {
      super(originalModel.getPixelSize());
      this.originalModel = originalModel;
   }

// The amount of gray is the max of the red, green, and blue
   protected int getGrayLevel(int pixel)
   {
      return Math.max(originalModel.getRed(pixel),
         Math.max(originalModel.getGreen(pixel),
            originalModel.getBlue(pixel)));
   }

// Leave the alpha values untouched
   public int getAlpha(int pixel)
   {
      return originalModel.getAlpha(pixel);
   }

// Since gray requires red, green and blue to be the same,
// use the same gray level value for red, green, and blue

   public int getRed(int pixel)
   {
      return getGrayLevel(pixel);
   }

   public int getGreen(int pixel)
   {
      return getGrayLevel(pixel);
   }

   public int getBlue(int pixel)
   {
      return getGrayLevel(pixel);
   }

// Normally, this method queries the red, green, blue and
// alpha values and returns them in the form 0xaarrggbb. To
// keep from computing the gray level 3 times, we just override
// this method, get the gray level once, and return it as the
// red, green, and blue, and add in the original alpha value.

   public int getRGB(int pixel)
   {
      int gray = getGrayLevel(pixel);
      return (getAlpha(pixel) << 24) + (gray << 16) +
         (gray << 8) + gray;
   }
}