001/*
002Copyright 2006 Jerry Huxtable
003
004Licensed under the Apache License, Version 2.0 (the "License");
005you may not use this file except in compliance with the License.
006You may obtain a copy of the License at
007
008   http://www.apache.org/licenses/LICENSE-2.0
009
010Unless required by applicable law or agreed to in writing, software
011distributed under the License is distributed on an "AS IS" BASIS,
012WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013See the License for the specific language governing permissions and
014limitations under the License.
015*/
016
017package com.jhlabs.image;
018
019import java.awt.*;
020import java.awt.image.*;
021
022/**
023 * A filter which converts an image to grayscale using the NTSC brightness calculation.
024 */
025public class GrayscaleFilter extends PointFilter {
026
027        public GrayscaleFilter() {
028                canFilterIndexColorModel = true;
029        }
030
031        public int filterRGB(int x, int y, int rgb) {
032                int a = rgb & 0xff000000;
033                int r = (rgb >> 16) & 0xff;
034                int g = (rgb >> 8) & 0xff;
035                int b = rgb & 0xff;
036//              rgb = (r + g + b) / 3;  // simple average
037                rgb = (r * 77 + g * 151 + b * 28) >> 8; // NTSC luma
038                return a | (rgb << 16) | (rgb << 8) | rgb;
039        }
040
041        public String toString() {
042                return "Colors/Grayscale";
043        }
044
045}
046
047