TransparentMaximumFilter.java

/*******************************************************************************
 * Copyright 2012 Geoscience Australia
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/
package au.gov.ga.earthsci.worldwind.common.layers.delegate.filters;

import java.awt.Rectangle;

import com.jhlabs.image.MaximumFilter;
import com.jhlabs.image.PixelUtils;

/**
 * Maximum (erode) filter that fixes the {@link MaximumFilter} to support
 * transparency.
 * 
 * @author Michael de Hoog (michael.dehoog@ga.gov.au)
 */
public class TransparentMaximumFilter extends MaximumFilter
{
	@Override
	protected int[] filterPixels(int width, int height, int[] inPixels, Rectangle transformedSpace)
	{
		int index = 0;
		int[] outPixels = new int[width * height];

		for (int y = 0; y < height; y++)
		{
			int yoffset = y * width;
			for (int x = 0; x < width; x++)
			{
				int pixel = inPixels[yoffset + x] & 0xff000000;
				for (int dy = -1; dy <= 1; dy++)
				{
					int iy = y + dy;
					int ioffset;
					if (0 <= iy && iy < height)
					{
						ioffset = iy * width;
						for (int dx = -1; dx <= 1; dx++)
						{
							int ix = x + dx;
							if (0 <= ix && ix < width)
							{
								pixel = PixelUtils.combinePixels(pixel, inPixels[ioffset + ix], PixelUtils.MAX);
							}
						}
					}
				}
				outPixels[index++] = pixel;
			}
		}
		return outPixels;
	}
}