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   25   
   26   package java.awt.image;
   27   
   28   import java.awt.image.ImageConsumer;
   29   import java.awt.image.ColorModel;
   30   
   31   /**
   32    * This class provides an easy way to create an ImageFilter which modifies
   33    * the pixels of an image in the default RGB ColorModel.  It is meant to
   34    * be used in conjunction with a FilteredImageSource object to produce
   35    * filtered versions of existing images.  It is an abstract class that
   36    * provides the calls needed to channel all of the pixel data through a
   37    * single method which converts pixels one at a time in the default RGB
   38    * ColorModel regardless of the ColorModel being used by the ImageProducer.
   39    * The only method which needs to be defined to create a useable image
   40    * filter is the filterRGB method.  Here is an example of a definition
   41    * of a filter which swaps the red and blue components of an image:
   42    * <pre>
   43    *
   44    *      class RedBlueSwapFilter extends RGBImageFilter {
   45    *          public RedBlueSwapFilter() {
   46    *              // The filter's operation does not depend on the
   47    *              // pixel's location, so IndexColorModels can be
   48    *              // filtered directly.
   49    *              canFilterIndexColorModel = true;
   50    *          }
   51    *
   52    *          public int filterRGB(int x, int y, int rgb) {
   53    *              return ((rgb & 0xff00ff00)
   54    *                      | ((rgb & 0xff0000) >> 16)
   55    *                      | ((rgb & 0xff) << 16));
   56    *          }
   57    *      }
   58    *
   59    * </pre>
   60    *
   61    * @see FilteredImageSource
   62    * @see ImageFilter
   63    * @see ColorModel#getRGBdefault
   64    *
   65    * @author      Jim Graham
   66    */
   67   public abstract class RGBImageFilter extends ImageFilter {
   68   
   69       /**
   70        * The <code>ColorModel</code> to be replaced by
   71        * <code>newmodel</code> when the user calls
   72        * {@link #substituteColorModel(ColorModel, ColorModel) substituteColorModel}.
   73        */
   74       protected ColorModel origmodel;
   75   
   76       /**
   77        * The <code>ColorModel</code> with which to
   78        * replace <code>origmodel</code> when the user calls
   79        * <code>substituteColorModel</code>.
   80        */
   81       protected ColorModel newmodel;
   82   
   83       /**
   84        * This boolean indicates whether or not it is acceptable to apply
   85        * the color filtering of the filterRGB method to the color table
   86        * entries of an IndexColorModel object in lieu of pixel by pixel
   87        * filtering.  Subclasses should set this variable to true in their
   88        * constructor if their filterRGB method does not depend on the
   89        * coordinate of the pixel being filtered.
   90        * @see #substituteColorModel
   91        * @see #filterRGB
   92        * @see IndexColorModel
   93        */
   94       protected boolean canFilterIndexColorModel;
   95   
   96       /**
   97        * If the ColorModel is an IndexColorModel and the subclass has
   98        * set the canFilterIndexColorModel flag to true, we substitute
   99        * a filtered version of the color model here and wherever
  100        * that original ColorModel object appears in the setPixels methods.
  101        * If the ColorModel is not an IndexColorModel or is null, this method
  102        * overrides the default ColorModel used by the ImageProducer and
  103        * specifies the default RGB ColorModel instead.
  104        * <p>
  105        * Note: This method is intended to be called by the
  106        * <code>ImageProducer</code> of the <code>Image</code> whose pixels
  107        * are being filtered. Developers using
  108        * this class to filter pixels from an image should avoid calling
  109        * this method directly since that operation could interfere
  110        * with the filtering operation.
  111        * @see ImageConsumer
  112        * @see ColorModel#getRGBdefault
  113        */
  114       public void setColorModel(ColorModel model) {
  115           if (canFilterIndexColorModel && (model instanceof IndexColorModel)) {
  116               ColorModel newcm = filterIndexColorModel((IndexColorModel)model);
  117               substituteColorModel(model, newcm);
  118               consumer.setColorModel(newcm);
  119           } else {
  120               consumer.setColorModel(ColorModel.getRGBdefault());
  121           }
  122       }
  123   
  124       /**
  125        * Registers two ColorModel objects for substitution.  If the oldcm
  126        * is encountered during any of the setPixels methods, the newcm
  127        * is substituted and the pixels passed through
  128        * untouched (but with the new ColorModel object).
  129        * @param oldcm the ColorModel object to be replaced on the fly
  130        * @param newcm the ColorModel object to replace oldcm on the fly
  131        */
  132       public void substituteColorModel(ColorModel oldcm, ColorModel newcm) {
  133           origmodel = oldcm;
  134           newmodel = newcm;
  135       }
  136   
  137       /**
  138        * Filters an IndexColorModel object by running each entry in its
  139        * color tables through the filterRGB function that RGBImageFilter
  140        * subclasses must provide.  Uses coordinates of -1 to indicate that
  141        * a color table entry is being filtered rather than an actual
  142        * pixel value.
  143        * @param icm the IndexColorModel object to be filtered
  144        * @exception NullPointerException if <code>icm</code> is null
  145        * @return a new IndexColorModel representing the filtered colors
  146        */
  147       public IndexColorModel filterIndexColorModel(IndexColorModel icm) {
  148           int mapsize = icm.getMapSize();
  149           byte r[] = new byte[mapsize];
  150           byte g[] = new byte[mapsize];
  151           byte b[] = new byte[mapsize];
  152           byte a[] = new byte[mapsize];
  153           icm.getReds(r);
  154           icm.getGreens(g);
  155           icm.getBlues(b);
  156           icm.getAlphas(a);
  157           int trans = icm.getTransparentPixel();
  158           boolean needalpha = false;
  159           for (int i = 0; i < mapsize; i++) {
  160               int rgb = filterRGB(-1, -1, icm.getRGB(i));
  161               a[i] = (byte) (rgb >> 24);
  162               if (a[i] != ((byte)0xff) && i != trans) {
  163                   needalpha = true;
  164               }
  165               r[i] = (byte) (rgb >> 16);
  166               g[i] = (byte) (rgb >> 8);
  167               b[i] = (byte) (rgb >> 0);
  168           }
  169           if (needalpha) {
  170               return new IndexColorModel(icm.getPixelSize(), mapsize,
  171                                          r, g, b, a);
  172           } else {
  173               return new IndexColorModel(icm.getPixelSize(), mapsize,
  174                                          r, g, b, trans);
  175           }
  176       }
  177   
  178       /**
  179        * Filters a buffer of pixels in the default RGB ColorModel by passing
  180        * them one by one through the filterRGB method.
  181        * @param x the X coordinate of the upper-left corner of the region
  182        *          of pixels
  183        * @param y the Y coordinate of the upper-left corner of the region
  184        *          of pixels
  185        * @param w the width of the region of pixels
  186        * @param h the height of the region of pixels
  187        * @param pixels the array of pixels
  188        * @param off the offset into the <code>pixels</code> array
  189        * @param scansize the distance from one row of pixels to the next
  190        *        in the array
  191        * @see ColorModel#getRGBdefault
  192        * @see #filterRGB
  193        */
  194       public void filterRGBPixels(int x, int y, int w, int h,
  195                                   int pixels[], int off, int scansize) {
  196           int index = off;
  197           for (int cy = 0; cy < h; cy++) {
  198               for (int cx = 0; cx < w; cx++) {
  199                   pixels[index] = filterRGB(x + cx, y + cy, pixels[index]);
  200                   index++;
  201               }
  202               index += scansize - w;
  203           }
  204           consumer.setPixels(x, y, w, h, ColorModel.getRGBdefault(),
  205                              pixels, off, scansize);
  206       }
  207   
  208       /**
  209        * If the ColorModel object is the same one that has already
  210        * been converted, then simply passes the pixels through with the
  211        * converted ColorModel. Otherwise converts the buffer of byte
  212        * pixels to the default RGB ColorModel and passes the converted
  213        * buffer to the filterRGBPixels method to be converted one by one.
  214        * <p>
  215        * Note: This method is intended to be called by the
  216        * <code>ImageProducer</code> of the <code>Image</code> whose pixels
  217        * are being filtered. Developers using
  218        * this class to filter pixels from an image should avoid calling
  219        * this method directly since that operation could interfere
  220        * with the filtering operation.
  221        * @see ColorModel#getRGBdefault
  222        * @see #filterRGBPixels
  223        */
  224       public void setPixels(int x, int y, int w, int h,
  225                             ColorModel model, byte pixels[], int off,
  226                             int scansize) {
  227           if (model == origmodel) {
  228               consumer.setPixels(x, y, w, h, newmodel, pixels, off, scansize);
  229           } else {
  230               int filteredpixels[] = new int[w];
  231               int index = off;
  232               for (int cy = 0; cy < h; cy++) {
  233                   for (int cx = 0; cx < w; cx++) {
  234                       filteredpixels[cx] = model.getRGB((pixels[index] & 0xff));
  235                       index++;
  236                   }
  237                   index += scansize - w;
  238                   filterRGBPixels(x, y + cy, w, 1, filteredpixels, 0, w);
  239               }
  240           }
  241       }
  242   
  243       /**
  244        * If the ColorModel object is the same one that has already
  245        * been converted, then simply passes the pixels through with the
  246        * converted ColorModel, otherwise converts the buffer of integer
  247        * pixels to the default RGB ColorModel and passes the converted
  248        * buffer to the filterRGBPixels method to be converted one by one.
  249        * Converts a buffer of integer pixels to the default RGB ColorModel
  250        * and passes the converted buffer to the filterRGBPixels method.
  251        * <p>
  252        * Note: This method is intended to be called by the
  253        * <code>ImageProducer</code> of the <code>Image</code> whose pixels
  254        * are being filtered. Developers using
  255        * this class to filter pixels from an image should avoid calling
  256        * this method directly since that operation could interfere
  257        * with the filtering operation.
  258        * @see ColorModel#getRGBdefault
  259        * @see #filterRGBPixels
  260        */
  261       public void setPixels(int x, int y, int w, int h,
  262                             ColorModel model, int pixels[], int off,
  263                             int scansize) {
  264           if (model == origmodel) {
  265               consumer.setPixels(x, y, w, h, newmodel, pixels, off, scansize);
  266           } else {
  267               int filteredpixels[] = new int[w];
  268               int index = off;
  269               for (int cy = 0; cy < h; cy++) {
  270                   for (int cx = 0; cx < w; cx++) {
  271                       filteredpixels[cx] = model.getRGB(pixels[index]);
  272                       index++;
  273                   }
  274                   index += scansize - w;
  275                   filterRGBPixels(x, y + cy, w, 1, filteredpixels, 0, w);
  276               }
  277           }
  278       }
  279   
  280       /**
  281        * Subclasses must specify a method to convert a single input pixel
  282        * in the default RGB ColorModel to a single output pixel.
  283        * @param x the X coordinate of the pixel
  284        * @param y the Y coordinate of the pixel
  285        * @param rgb the integer pixel representation in the default RGB
  286        *            color model
  287        * @return a filtered pixel in the default RGB color model.
  288        * @see ColorModel#getRGBdefault
  289        * @see #filterRGBPixels
  290        */
  291       public abstract int filterRGB(int x, int y, int rgb);
  292   }

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