/* RGBImageFilter.java -- Java class for filtering Pixels by RGB values
   Copyright (C) 1999, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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02110-1301 USA.

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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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package java.awt.image;

/**
 * A filter designed to filter images in the default RGBColorModel regardless of 
 * the ImageProducer's ColorModel.
 *
 * @author Mark Benvenuto (mcb54@columbia.edu)
 */
public abstract class RGBImageFilter extends ImageFilter
{
    protected ColorModel origmodel;

    protected ColorModel newmodel;
    
    /**
       Specifies whether to apply the filter to the index entries of the 
       IndexColorModel. Subclasses should set this to true if the filter 
       does not depend on the pixel's coordinate.
     */
    protected boolean canFilterIndexColorModel = false;

    /**
       Construct new RGBImageFilter.
     */
    public RGBImageFilter() 
    {
    }

    /**
     * Sets the ColorModel used to filter with. If the specified ColorModel is IndexColorModel 
     * and canFilterIndexColorModel is true, we subsitute the ColorModel for a filtered one
     * here and in setPixels whenever the original one appears. Otherwise overrides the default
     * ColorModel of ImageProducer and specifies the default RGBColorModel
     *
     * @param model the color model to be used most often by setPixels
     * @see ColorModel */
    public void setColorModel(ColorModel model) 
    {
	origmodel = model;
	newmodel = model;

	if( ( model instanceof IndexColorModel) && canFilterIndexColorModel  ) {
		newmodel = filterIndexColorModel( (IndexColorModel) model );
		consumer.setColorModel(newmodel);
	    }
	else {
		consumer.setColorModel(ColorModel.getRGBdefault());
	}
    }
    
    /**
       Registers a new ColorModel to subsitute for the old ColorModel when 
       setPixels encounters the a pixel with the old ColorModel. The pixel 
       remains unchanged except for a new ColorModel.
       
       @param oldcm the old ColorModel
       @param newcm the new ColorModel
     */
    public void substituteColorModel(ColorModel oldcm,
				     ColorModel newcm)
    {
	origmodel = oldcm;
	newmodel = newcm;
    }

    /**
       Filters an IndexColorModel through the filterRGB function. Uses
       coordinates of -1 to indicate its filtering an index and not a pixel.

       @param icm an IndexColorModel to filter
     */
    public IndexColorModel filterIndexColorModel(IndexColorModel icm) 
    {
	int len = icm.getMapSize(), rgb;
	byte reds[] = new byte[len], greens[] = new byte[len], blues[] = new byte[len], alphas[]  = new byte[len];
	
	icm.getAlphas( alphas );
	icm.getReds( reds );
	icm.getGreens( greens );
	icm.getBlues( blues );

	for( int i = 0; i < len; i++ )
	    {
		rgb = filterRGB( -1, -1, makeColor ( alphas[i], reds[i], greens[i], blues[i] ) );
		alphas[i] = (byte)(( 0xff000000 & rgb ) >> 24);
		reds[i] = (byte)(( 0xff0000 & rgb ) >> 16);
		greens[i] = (byte)(( 0xff00 & rgb ) >> 8);
		blues[i] = (byte)(0xff & rgb);
	    }
	return new IndexColorModel( icm.getPixelSize(), len, reds, greens, blues, alphas );
    }

    private int makeColor( byte a, byte r, byte g, byte b )
    {
	return ( 0xff000000 & (a << 24) | 0xff0000 & (r << 16) | 0xff00 & (g << 8) | 0xff & b ); 
    }

    /**
       This functions filters a set of RGB pixels through filterRGB.

       @param x the x coordinate of the rectangle
       @param y the y coordinate of the rectangle
       @param w the width of the rectangle
       @param h the height of the rectangle
       @param pixels the array of pixel values
       @param offset the index of the first pixels in the <code>pixels</code> array
       @param scansize the width to use in extracting pixels from the <code>pixels</code> array
    */
    public void filterRGBPixels(int x, int y, int w, int h, int[] pixels,
				int offset, int scansize)
    {
      for (int yp = 0; yp < h; yp++)
	{
	  for (int xp = 0; xp < w; xp++)
	    {
	      pixels[offset + xp] = filterRGB(xp + x, yp + y, pixels[offset + xp]);
	    }
	  offset += scansize;
	}
    }


    /**
     * If the ColorModel is the same ColorModel which as already converted 
     * then it converts it the converted ColorModel. Otherwise it passes the 
     * array of pixels through filterRGBpixels.
     *
     * @param x the x coordinate of the rectangle
     * @param y the y coordinate of the rectangle
     * @param w the width of the rectangle
     * @param h the height of the rectangle
     * @param model the <code>ColorModel</code> used to translate the pixels
     * @param pixels the array of pixel values
     * @param offset the index of the first pixels in the <code>pixels</code> array
     * @param scansize the width to use in extracting pixels from the <code>pixels</code> array
     */
    public void setPixels(int x, int y, int w, int h, 
                          ColorModel model, byte[] pixels,
                          int offset, int scansize)
    {
	if(model == origmodel && (model instanceof IndexColorModel) && canFilterIndexColorModel)
	{
	    consumer.setPixels(x, y, w, h, newmodel, pixels, offset, scansize);
	}
	else
	{
	    int intPixels[] =
		convertColorModelToDefault( x, y, w, h, model, pixels, offset, scansize );
	    filterRGBPixels( x, y, w, h, intPixels, offset, scansize );
	    consumer.setPixels(x, y, w, h, ColorModel.getRGBdefault(), intPixels, offset, scansize);
	}
    }

    /**
     * This function delivers a rectangle of pixels where any
     * pixel(m,n) is stored in the array as an <code>int</code> at
     * index (n * scansize + m + offset).  
     *
     * @param x the x coordinate of the rectangle
     * @param y the y coordinate of the rectangle
     * @param w the width of the rectangle
     * @param h the height of the rectangle
     * @param model the <code>ColorModel</code> used to translate the pixels
     * @param pixels the array of pixel values
     * @param offset the index of the first pixels in the <code>pixels</code> array
     * @param scansize the width to use in extracting pixels from the <code>pixels</code> array
     */
    public void setPixels(int x, int y, int w, int h, 
                          ColorModel model, int[] pixels,
                          int offset, int scansize)
    {
	if(model == origmodel && (model instanceof IndexColorModel) && canFilterIndexColorModel)
	{
	    consumer.setPixels(x, y, w, h, newmodel, pixels, offset, scansize);
	}
	else
	{
	    //FIXME: Store the filtered pixels in a separate temporary buffer?
	  convertColorModelToDefault( x, y, w, h, model, pixels, offset, scansize );
	  filterRGBPixels( x, y, w, h, pixels, offset, scansize );
	  consumer.setPixels(x, y, w, h, ColorModel.getRGBdefault(), pixels, offset, scansize);
	}
    }

    private int[] convertColorModelToDefault(int x, int y, int w, int h, 
                                            ColorModel model, byte pixels[],
                                            int offset, int scansize)
    {
	int intPixels[] = new int[pixels.length];
	for (int i = 0; i < pixels.length; i++)
	    intPixels[i] = makeColorbyDefaultCM(model, pixels[i]);
	return intPixels;
    }

    private void convertColorModelToDefault(int x, int y, int w, int h, 
                                            ColorModel model, int pixels[],
                                            int offset, int scansize)
    {
	for (int i = 0; i < pixels.length; i++)
	    pixels[i] = makeColorbyDefaultCM(model, pixels[i]);
    }

    private int makeColorbyDefaultCM(ColorModel model, byte rgb) 
    {
	return makeColor( model.getAlpha( rgb ) * 4, model.getRed( rgb ) * 4, model.getGreen( rgb ) * 4, model.getBlue( rgb ) * 4 );
    }

    private int makeColorbyDefaultCM(ColorModel model, int rgb) 
    {
	return makeColor( model.getAlpha( rgb ), model.getRed( rgb ), model.getGreen( rgb ), model.getBlue( rgb ) );
    }

    private int makeColor( int a, int r, int g, int b )
    {
	return (int)( 0xff000000 & (a << 24) | 0xff0000 & (r << 16) | 0xff00 & (g << 8) | 0xff & b ); 
    }


    /**
       Filters a single pixel from the default ColorModel.

       @param x x-coordinate
       @param y y-coordinate
       @param rgb color
     */
    public abstract int filterRGB(int x,
				  int y,
				  int rgb);
}
