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package java.awt.image;

import java.awt.image.ImageConsumer;
import java.awt.image.ColorModel;


This class provides an easy way to create an ImageFilter which modifies
the pixels of an image in the default RGB ColorModel.  It is meant to
be used in conjunction with a FilteredImageSource object to produce
filtered versions of existing images.  It is an abstract class that
provides the calls needed to channel all of the pixel data through a
single method which converts pixels one at a time in the default RGB
ColorModel regardless of the ColorModel being used by the ImageProducer.
The only method which needs to be defined to create a useable image
filter is the filterRGB method.  Here is an example of a definition
of a filter which swaps the red and blue components of an image:


     class RedBlueSwapFilter extends RGBImageFilter {
         public RedBlueSwapFilter() {
             // The filter's operation does not depend on the
             // pixel's location, so IndexColorModels can be
             // filtered directly.
             canFilterIndexColorModel = true;
         }
         public int filterRGB(int x, int y, int rgb) {
             return ((rgb & 0xff00ff00)
                     | ((rgb & 0xff0000) >> 16)
                     | ((rgb & 0xff) << 16));
         }
     }



Author:     Jim Graham
See Also:
/**
 * This class provides an easy way to create an ImageFilter which modifies
 * the pixels of an image in the default RGB ColorModel.  It is meant to
 * be used in conjunction with a FilteredImageSource object to produce
 * filtered versions of existing images.  It is an abstract class that
 * provides the calls needed to channel all of the pixel data through a
 * single method which converts pixels one at a time in the default RGB
 * ColorModel regardless of the ColorModel being used by the ImageProducer.
 * The only method which needs to be defined to create a useable image
 * filter is the filterRGB method.  Here is an example of a definition
 * of a filter which swaps the red and blue components of an image:
 * <pre>{@code
 *
 *      class RedBlueSwapFilter extends RGBImageFilter {
 *          public RedBlueSwapFilter() {
 *              // The filter's operation does not depend on the
 *              // pixel's location, so IndexColorModels can be
 *              // filtered directly.
 *              canFilterIndexColorModel = true;
 *          }
 *
 *          public int filterRGB(int x, int y, int rgb) {
 *              return ((rgb & 0xff00ff00)
 *                      | ((rgb & 0xff0000) >> 16)
 *                      | ((rgb & 0xff) << 16));
 *          }
 *      }
 *
 * }</pre>
 *
 * @see FilteredImageSource
 * @see ImageFilter
 * @see ColorModel#getRGBdefault
 *
 * @author      Jim Graham
 */
public abstract class RGBImageFilter extends ImageFilter {

    
The ColorModel to be replaced by newmodel when the user calls substituteColorModel. 
/**
     * The {@code ColorModel} to be replaced by
     * {@code newmodel} when the user calls
     * {@link #substituteColorModel(ColorModel, ColorModel) substituteColorModel}.
     */
    protected ColorModel origmodel;

    
The ColorModel with which to replace origmodel when the user calls substituteColorModel. 
/**
     * The {@code ColorModel} with which to
     * replace {@code origmodel} when the user calls
     * {@code substituteColorModel}.
     */
    protected ColorModel newmodel;

    
This boolean indicates whether or not it is acceptable to apply
the color filtering of the filterRGB method to the color table
entries of an IndexColorModel object in lieu of pixel by pixel
filtering.  Subclasses should set this variable to true in their
constructor if their filterRGB method does not depend on the
coordinate of the pixel being filtered.

See Also:
/**
     * This boolean indicates whether or not it is acceptable to apply
     * the color filtering of the filterRGB method to the color table
     * entries of an IndexColorModel object in lieu of pixel by pixel
     * filtering.  Subclasses should set this variable to true in their
     * constructor if their filterRGB method does not depend on the
     * coordinate of the pixel being filtered.
     * @see #substituteColorModel
     * @see #filterRGB
     * @see IndexColorModel
     */
    protected boolean canFilterIndexColorModel;

    
If the ColorModel is an IndexColorModel and the subclass has
set the canFilterIndexColorModel flag to true, we substitute
a filtered version of the color model here and wherever
that original ColorModel object appears in the setPixels methods.
If the ColorModel is not an IndexColorModel or is null, this method
overrides the default ColorModel used by the ImageProducer and
specifies the default RGB ColorModel instead.

 Note: This method is intended to be called by the ImageProducer of the Image whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation. 
See Also:
/**
     * If the ColorModel is an IndexColorModel and the subclass has
     * set the canFilterIndexColorModel flag to true, we substitute
     * a filtered version of the color model here and wherever
     * that original ColorModel object appears in the setPixels methods.
     * If the ColorModel is not an IndexColorModel or is null, this method
     * overrides the default ColorModel used by the ImageProducer and
     * specifies the default RGB ColorModel instead.
     * <p>
     * Note: This method is intended to be called by the
     * {@code ImageProducer} of the {@code Image} whose pixels
     * are being filtered. Developers using
     * this class to filter pixels from an image should avoid calling
     * this method directly since that operation could interfere
     * with the filtering operation.
     * @see ImageConsumer
     * @see ColorModel#getRGBdefault
     */
    public void setColorModel(ColorModel model) {
        if (canFilterIndexColorModel && (model instanceof IndexColorModel)) {
            ColorModel newcm = filterIndexColorModel((IndexColorModel)model);
            substituteColorModel(model, newcm);
            consumer.setColorModel(newcm);
        } else {
            consumer.setColorModel(ColorModel.getRGBdefault());
        }
    }

    
Registers two ColorModel objects for substitution.  If the oldcm
is encountered during any of the setPixels methods, the newcm
is substituted and the pixels passed through
untouched (but with the new ColorModel object).

Params:
  • oldcm – the ColorModel object to be replaced on the fly
  • newcm – the ColorModel object to replace oldcm on the fly
/**
     * Registers two ColorModel objects for substitution.  If the oldcm
     * is encountered during any of the setPixels methods, the newcm
     * is substituted and the pixels passed through
     * untouched (but with the new ColorModel object).
     * @param oldcm the ColorModel object to be replaced on the fly
     * @param newcm the ColorModel object to replace oldcm on the fly
     */
    public void substituteColorModel(ColorModel oldcm, ColorModel newcm) {
        origmodel = oldcm;
        newmodel = newcm;
    }

    
Filters an IndexColorModel object by running each entry in its
color tables through the filterRGB function that RGBImageFilter
subclasses must provide.  Uses coordinates of -1 to indicate that
a color table entry is being filtered rather than an actual
pixel value.

Params:
  • icm – the IndexColorModel object to be filtered
Throws:
Returns:a new IndexColorModel representing the filtered colors
/**
     * Filters an IndexColorModel object by running each entry in its
     * color tables through the filterRGB function that RGBImageFilter
     * subclasses must provide.  Uses coordinates of -1 to indicate that
     * a color table entry is being filtered rather than an actual
     * pixel value.
     * @param icm the IndexColorModel object to be filtered
     * @exception NullPointerException if {@code icm} is null
     * @return a new IndexColorModel representing the filtered colors
     */
    public IndexColorModel filterIndexColorModel(IndexColorModel icm) {
        int mapsize = icm.getMapSize();
        byte r[] = new byte[mapsize];
        byte g[] = new byte[mapsize];
        byte b[] = new byte[mapsize];
        byte a[] = new byte[mapsize];
        icm.getReds(r);
        icm.getGreens(g);
        icm.getBlues(b);
        icm.getAlphas(a);
        int trans = icm.getTransparentPixel();
        boolean needalpha = false;
        for (int i = 0; i < mapsize; i++) {
            int rgb = filterRGB(-1, -1, icm.getRGB(i));
            a[i] = (byte) (rgb >> 24);
            if (a[i] != ((byte)0xff) && i != trans) {
                needalpha = true;
            }
            r[i] = (byte) (rgb >> 16);
            g[i] = (byte) (rgb >> 8);
            b[i] = (byte) (rgb >> 0);
        }
        if (needalpha) {
            return new IndexColorModel(icm.getPixelSize(), mapsize,
                                       r, g, b, a);
        } else {
            return new IndexColorModel(icm.getPixelSize(), mapsize,
                                       r, g, b, trans);
        }
    }

    
Filters a buffer of pixels in the default RGB ColorModel by passing
them one by one through the filterRGB method.

Params:
  • x – the X coordinate of the upper-left corner of the region
         of pixels
  • y – the Y coordinate of the upper-left corner of the region
         of pixels
  • w – the width of the region of pixels
  • h – the height of the region of pixels
  • pixels – the array of pixels
  • off – the offset into the pixels array
  • scansize – the distance from one row of pixels to the next
       in the array
See Also:
/**
     * Filters a buffer of pixels in the default RGB ColorModel by passing
     * them one by one through the filterRGB method.
     * @param x the X coordinate of the upper-left corner of the region
     *          of pixels
     * @param y the Y coordinate of the upper-left corner of the region
     *          of pixels
     * @param w the width of the region of pixels
     * @param h the height of the region of pixels
     * @param pixels the array of pixels
     * @param off the offset into the {@code pixels} array
     * @param scansize the distance from one row of pixels to the next
     *        in the array
     * @see ColorModel#getRGBdefault
     * @see #filterRGB
     */
    public void filterRGBPixels(int x, int y, int w, int h,
                                int pixels[], int off, int scansize) {
        int index = off;
        for (int cy = 0; cy < h; cy++) {
            for (int cx = 0; cx < w; cx++) {
                pixels[index] = filterRGB(x + cx, y + cy, pixels[index]);
                index++;
            }
            index += scansize - w;
        }
        consumer.setPixels(x, y, w, h, ColorModel.getRGBdefault(),
                           pixels, off, scansize);
    }

    
If the ColorModel object is the same one that has already
been converted, then simply passes the pixels through with the
converted ColorModel. Otherwise converts the buffer of byte
pixels to the default RGB ColorModel and passes the converted
buffer to the filterRGBPixels method to be converted one by one.

 Note: This method is intended to be called by the ImageProducer of the Image whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation. 
See Also:
/**
     * If the ColorModel object is the same one that has already
     * been converted, then simply passes the pixels through with the
     * converted ColorModel. Otherwise converts the buffer of byte
     * pixels to the default RGB ColorModel and passes the converted
     * buffer to the filterRGBPixels method to be converted one by one.
     * <p>
     * Note: This method is intended to be called by the
     * {@code ImageProducer} of the {@code Image} whose pixels
     * are being filtered. Developers using
     * this class to filter pixels from an image should avoid calling
     * this method directly since that operation could interfere
     * with the filtering operation.
     * @see ColorModel#getRGBdefault
     * @see #filterRGBPixels
     */
    public void setPixels(int x, int y, int w, int h,
                          ColorModel model, byte pixels[], int off,
                          int scansize) {
        if (model == origmodel) {
            consumer.setPixels(x, y, w, h, newmodel, pixels, off, scansize);
        } else {
            int filteredpixels[] = new int[w];
            int index = off;
            for (int cy = 0; cy < h; cy++) {
                for (int cx = 0; cx < w; cx++) {
                    filteredpixels[cx] = model.getRGB((pixels[index] & 0xff));
                    index++;
                }
                index += scansize - w;
                filterRGBPixels(x, y + cy, w, 1, filteredpixels, 0, w);
            }
        }
    }

    
If the ColorModel object is the same one that has already
been converted, then simply passes the pixels through with the
converted ColorModel, otherwise converts the buffer of integer
pixels to the default RGB ColorModel and passes the converted
buffer to the filterRGBPixels method to be converted one by one.
Converts a buffer of integer pixels to the default RGB ColorModel
and passes the converted buffer to the filterRGBPixels method.

 Note: This method is intended to be called by the ImageProducer of the Image whose pixels are being filtered. Developers using this class to filter pixels from an image should avoid calling this method directly since that operation could interfere with the filtering operation. 
See Also:
/**
     * If the ColorModel object is the same one that has already
     * been converted, then simply passes the pixels through with the
     * converted ColorModel, otherwise converts the buffer of integer
     * pixels to the default RGB ColorModel and passes the converted
     * buffer to the filterRGBPixels method to be converted one by one.
     * Converts a buffer of integer pixels to the default RGB ColorModel
     * and passes the converted buffer to the filterRGBPixels method.
     * <p>
     * Note: This method is intended to be called by the
     * {@code ImageProducer} of the {@code Image} whose pixels
     * are being filtered. Developers using
     * this class to filter pixels from an image should avoid calling
     * this method directly since that operation could interfere
     * with the filtering operation.
     * @see ColorModel#getRGBdefault
     * @see #filterRGBPixels
     */
    public void setPixels(int x, int y, int w, int h,
                          ColorModel model, int pixels[], int off,
                          int scansize) {
        if (model == origmodel) {
            consumer.setPixels(x, y, w, h, newmodel, pixels, off, scansize);
        } else {
            int filteredpixels[] = new int[w];
            int index = off;
            for (int cy = 0; cy < h; cy++) {
                for (int cx = 0; cx < w; cx++) {
                    filteredpixels[cx] = model.getRGB(pixels[index]);
                    index++;
                }
                index += scansize - w;
                filterRGBPixels(x, y + cy, w, 1, filteredpixels, 0, w);
            }
        }
    }

    
Subclasses must specify a method to convert a single input pixel
in the default RGB ColorModel to a single output pixel.

Params:
  • x – the X coordinate of the pixel
  • y – the Y coordinate of the pixel
  • rgb – the integer pixel representation in the default RGB
           color model
See Also:
Returns:a filtered pixel in the default RGB color model.
/**
     * Subclasses must specify a method to convert a single input pixel
     * in the default RGB ColorModel to a single output pixel.
     * @param x the X coordinate of the pixel
     * @param y the Y coordinate of the pixel
     * @param rgb the integer pixel representation in the default RGB
     *            color model
     * @return a filtered pixel in the default RGB color model.
     * @see ColorModel#getRGBdefault
     * @see #filterRGBPixels
     */
    public abstract int filterRGB(int x, int y, int rgb);
}