source: trunk/src_apollo/org/apollo/gui/FastAlphaEffect.java@ 315

package org.apollo.gui;

import java.awt.Rectangle;
import java.awt.image.ColorModel;
import java.awt.image.WritableRaster;

/**
 * I remember this little trick back in days of DirectDraw:
 * 
 * A fast technique for drawing a 50% alpha blend.
 * 
 * @author Brook Novak
 *
 */
public final class FastAlphaEffect {

        private FastAlphaEffect() {
        }

        /**
         * @see FastAlphaEffect#fastBlendSingleColor(WritableRaster, ColorModel, int, int, int, int, int)
         * @param raster
         * @param colorModel
         * @param area
         * @param rgb
         */
        public static final void fastBlendSingleColor(
                        WritableRaster raster,
                        ColorModel colorModel,
                        Rectangle area,
                        int rgb) {
                fastBlendSingleColor(raster, colorModel, area.x, area.y, area.width, area.height, rgb);
        }
        
        /**
         * 
         * @param raster
         * 
         * @param colorModel
         * 
         * @param x
         * 
         * @param y
         * 
         * @param width
         * 
         * @param height
         * 
         * @param rgb
         *              The color to blend.
         * 
         * 
         * @throws NullPointerException
         *                      If raster or colorModel is null
         * 
         */
        public static final void fastBlendSingleColor(
                        WritableRaster raster,
                        ColorModel colorModel,
                        int x, int y, 
                        int width, int height,
                        int rgb) {
                
                if (raster == null)
                        throw new NullPointerException("raster");
                else if (colorModel == null)
                        throw new NullPointerException("raster");
                
                int endcol = x + width;
                int endrow = y + height;
                
                // Clamp bounds
                if (x < 0) x = 0;
                if (y < 0) y = 0;
                if (endcol >= raster.getWidth()) endcol = raster.getWidth() - 1;
                if (endrow >= raster.getHeight()) endrow = raster.getHeight() - 1;
                
                // Safe note: If endrow <= y or endcol <= x then the loops wont be entered

                boolean offsetStart = false;
                
                Object colorData = colorModel.getDataElements(rgb, null);

                for (int row = y; row < endrow; row++) {
                        
                                
                        for (int col = (offsetStart) ? x + 1 : x; col < endcol; col+=2) { // paint every second pixel
                
                                        raster.setDataElements(col, row, colorData);
                                
                        }
                        
                        // Get checker effect
                        offsetStart = !offsetStart;
                
                }
                
        }
}