001    /*
002    *
003    
004    Licensed under the Apache License, Version 2.0 (the "License");
005    you may not use this file except in compliance with the License.
006    You may obtain a copy of the License at
007    
008       http://www.apache.org/licenses/LICENSE-2.0
009    
010    Unless required by applicable law or agreed to in writing, software
011    distributed under the License is distributed on an "AS IS" BASIS,
012    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013    See the License for the specific language governing permissions and
014    limitations under the License.
015    */
016    
017    package railo.runtime.img.composite;
018    
019    import java.awt.CompositeContext;
020    import java.awt.RenderingHints;
021    import java.awt.image.ColorModel;
022    
023    public final class ScreenComposite extends RGBComposite {
024    
025            public ScreenComposite( float alpha ) {
026            super( alpha );
027            }
028    
029            public CompositeContext createContext( ColorModel srcColorModel, ColorModel dstColorModel, RenderingHints hints ) {
030                    return new Context( extraAlpha, srcColorModel, dstColorModel );
031            }
032    
033        static class Context extends RGBCompositeContext {
034            public Context( float alpha, ColorModel srcColorModel, ColorModel dstColorModel ) {
035                super( alpha, srcColorModel, dstColorModel );
036            }
037    
038            public void composeRGB( int[] src, int[] dst, float alpha ) {
039                int w = src.length;
040    
041                for ( int i = 0; i < w; i += 4 ) {
042                    int sr = src[i];
043                    int dir = dst[i];
044                    int sg = src[i+1];
045                    int dig = dst[i+1];
046                    int sb = src[i+2];
047                    int dib = dst[i+2];
048                    int sa = src[i+3];
049                    int dia = dst[i+3];
050                    int dor, dog, dob;
051    
052                    int t = (255-dir) * (255-sr) + 0x80;
053                    dor = 255 - ( ((t >> 8) + t) >> 8 );
054                    t = (255-dig) * (255-sg) + 0x80;
055                    dog = 255 - ( ((t >> 8) + t) >> 8 );
056                    t = (255-dib) * (255-sb) + 0x80;
057                    dob = 255 - ( ((t >> 8) + t) >> 8 );
058    
059                    float a = alpha*sa/255f;
060                    float ac = 1-a;
061    
062                    dst[i] = (int)(a*dor + ac*dir);
063                    dst[i+1] = (int)(a*dog + ac*dig);
064                    dst[i+2] = (int)(a*dob + ac*dib);
065                    dst[i+3] = (int)(sa*alpha + dia*ac);
066                }
067            }
068        }
069    
070    }