path: root/java/awt/image/ConvolveOp.java

/* ConvolveOp.java --
   Copyright (C) 2004, 2005, 2006, Free Software Foundation -- ConvolveOp

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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permission to link this library with independent modules to produce an
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package java.awt.image;

import java.awt.RenderingHints;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;

/**
 * Convolution filter.
 * 
 * ConvolveOp convolves the source image with a Kernel to generate a
 * destination image.  This involves multiplying each pixel and its neighbors
 * with elements in the kernel to compute a new pixel.
 * 
 * Each band in a Raster is convolved and copied to the destination Raster.
 * For BufferedImages, convolution is applied to all components.  Color 
 * conversion will be applied if needed.
 * 
 * Note that this filter ignores whether the source or destination is alpha
 * premultiplied.  The reference spec states that data will be premultiplied
 * prior to convolving and divided back out afterwards (if needed), but testing
 * has shown that this is not the case with their implementation.
 * 
 * @author jlquinn@optonline.net
 */
public class ConvolveOp implements BufferedImageOp, RasterOp
{
  /** Edge pixels are set to 0. */
  public static final int EDGE_ZERO_FILL = 0;
  
  /** Edge pixels are copied from the source. */
  public static final int EDGE_NO_OP = 1;
  
  private Kernel kernel;
  private int edge;
  private RenderingHints hints;

  /**
   * Construct a ConvolveOp.
   * 
   * The edge condition specifies that pixels outside the area that can be
   * filtered are either set to 0 or copied from the source image.
   * 
   * @param kernel The kernel to convolve with.
   * @param edgeCondition Either EDGE_ZERO_FILL or EDGE_NO_OP.
   * @param hints Rendering hints for color conversion, or null.
   */
  public ConvolveOp(Kernel kernel,
      				int edgeCondition,
      				RenderingHints hints)
  {
    this.kernel = kernel;
    edge = edgeCondition;
    this.hints = hints;
  }
  
  /**
   * Construct a ConvolveOp.
   * 
   * The edge condition defaults to EDGE_ZERO_FILL.
   * 
   * @param kernel The kernel to convolve with.
   */
  public ConvolveOp(Kernel kernel)
  {
    this.kernel = kernel;
    edge = EDGE_ZERO_FILL;
    hints = null;
  }

  /**
   * Converts the source image using the kernel specified in the
   * constructor.  The resulting image is stored in the destination image if one
   * is provided; otherwise a new BufferedImage is created and returned. 
   * 
   * The source and destination BufferedImage (if one is supplied) must have
   * the same dimensions.
   *
   * @param src The source image.
   * @param dst The destination image.
   * @throws IllegalArgumentException if the rasters and/or color spaces are
   *            incompatible.
   * @return The convolved image.
   */
  public final BufferedImage filter(BufferedImage src, BufferedImage dst)
  {
    if (src == dst)
      throw new IllegalArgumentException("Source and destination images " +
            "cannot be the same.");
    
    if (dst == null)
      dst = createCompatibleDestImage(src, src.getColorModel());
    
    // Make sure source image is premultiplied
    BufferedImage src1 = src;
    // The spec says we should do this, but mauve testing shows that Sun's
    // implementation does not check this.
    /*
    if (!src.isAlphaPremultiplied())
    {
      src1 = createCompatibleDestImage(src, src.getColorModel());
      src.copyData(src1.getRaster());
      src1.coerceData(true);
    }
    */

    BufferedImage dst1 = dst;
    if (src1.getColorModel().getColorSpace().getType() != dst.getColorModel().getColorSpace().getType())
      dst1 = createCompatibleDestImage(src, src.getColorModel());

    filter(src1.getRaster(), dst1.getRaster());
    
    // Since we don't coerceData above, we don't need to divide it back out.
    // This is wrong (one mauve test specifically tests converting a non-
    // premultiplied image to a premultiplied image, and it shows that Sun
    // simply ignores the premultipled flag, contrary to the spec), but we
    // mimic it for compatibility.
    /*
	if (! dst.isAlphaPremultiplied())
	  dst1.coerceData(false);
    */

    // Convert between color models if needed
    if (dst1 != dst)
      new ColorConvertOp(hints).filter(dst1, dst);

    return dst;
  }

  /**
   * Creates an empty BufferedImage with the size equal to the source and the
   * correct number of bands. The new image is created with the specified 
   * ColorModel, or if no ColorModel is supplied, an appropriate one is chosen.
   *
   * @param src The source image.
   * @param dstCM A color model for the destination image (may be null).
   * @return The new compatible destination image.
   */
  public BufferedImage createCompatibleDestImage(BufferedImage src,
                                                 ColorModel dstCM)
  {
    if (dstCM != null)
      return new BufferedImage(dstCM,
                               src.getRaster().createCompatibleWritableRaster(),
                               src.isAlphaPremultiplied(), null);

    return new BufferedImage(src.getWidth(), src.getHeight(), src.getType());
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#getRenderingHints()
   */
  public final RenderingHints getRenderingHints()
  {
    return hints;
  }
  
  /**
   * Get the edge condition for this Op.
   * 
   * @return The edge condition.
   */
  public int getEdgeCondition()
  {
    return edge;
  }
  
  /**
   * Returns (a clone of) the convolution kernel.
   *
   * @return The convolution kernel.
   */
  public final Kernel getKernel()
  {
    return (Kernel) kernel.clone();
  }

  /**
   * Converts the source raster using the kernel specified in the constructor.  
   * The resulting raster is stored in the destination raster if one is 
   * provided; otherwise a new WritableRaster is created and returned.
   * 
   * If the convolved value for a sample is outside the range of [0-255], it
   * will be clipped.
   * 
   * The source and destination raster (if one is supplied) cannot be the same,
   * and must also have the same dimensions.
   *
   * @param src The source raster.
   * @param dest The destination raster.
   * @throws IllegalArgumentException if the rasters identical.
   * @throws ImagingOpException if the convolution is not possible.
   * @return The transformed raster.
   */
  public final WritableRaster filter(Raster src, WritableRaster dest)
  {
    if (src == dest)
      throw new IllegalArgumentException("src == dest is not allowed.");
    if (kernel.getWidth() > src.getWidth() 
        || kernel.getHeight() > src.getHeight())
      throw new ImagingOpException("The kernel is too large.");
    if (dest == null)
      dest = createCompatibleDestRaster(src);
    else if (src.getNumBands() != dest.getNumBands())
      throw new ImagingOpException("src and dest have different band counts.");

    // calculate the borders that the op can't reach...
    int kWidth = kernel.getWidth();
    int kHeight = kernel.getHeight();
    int left = kernel.getXOrigin();
    int right = Math.max(kWidth - left - 1, 0);
    int top = kernel.getYOrigin();
    int bottom = Math.max(kHeight - top - 1, 0);
    
    // Calculate max sample values for clipping
    int[] maxValue = src.getSampleModel().getSampleSize();
    for (int i = 0; i < maxValue.length; i++)
      maxValue[i] = (int)Math.pow(2, maxValue[i]) - 1;
    
    // process the region that is reachable...
    int regionW = src.width - left - right;
    int regionH = src.height - top - bottom;
    float[] kvals = kernel.getKernelData(null);
    float[] tmp = new float[kWidth * kHeight];

    for (int x = 0; x < regionW; x++)
      {
        for (int y = 0; y < regionH; y++)
          {
            // FIXME: This needs a much more efficient implementation
            for (int b = 0; b < src.getNumBands(); b++)
            {
              float v = 0;
              src.getSamples(x, y, kWidth, kHeight, b, tmp);
              for (int i = 0; i < tmp.length; i++)
                v += tmp[tmp.length - i - 1] * kvals[i];
                // FIXME: in the above line, I've had to reverse the order of 
                // the samples array to make the tests pass.  I haven't worked 
                // out why this is necessary.

              // This clipping is is undocumented, but determined by testing.
              if (v > maxValue[b])
                v = maxValue[b];
              else if (v < 0)
                v = 0;

              dest.setSample(x + kernel.getXOrigin(), y + kernel.getYOrigin(), 
                             b, v);
            }
          }
      }
    
    // fill in the top border
    fillEdge(src, dest, 0, 0, src.width, top, edge);
    
    // fill in the bottom border
    fillEdge(src, dest, 0, src.height - bottom, src.width, bottom, edge);
    
    // fill in the left border
    fillEdge(src, dest, 0, top, left, regionH, edge);
    
    // fill in the right border
    fillEdge(src, dest, src.width - right, top, right, regionH, edge);
    
    return dest;  
  }
  
  /**
   * Fills a range of pixels (typically at the edge of a raster) with either
   * zero values (if <code>edgeOp</code> is <code>EDGE_ZERO_FILL</code>) or the 
   * corresponding pixel values from the source raster (if <code>edgeOp</code>
   * is <code>EDGE_NO_OP</code>).  This utility method is called by the 
   * {@link #fillEdge(Raster, WritableRaster, int, int, int, int, int)} method.
   * 
   * @param src  the source raster.
   * @param dest  the destination raster.
   * @param x  the x-coordinate of the top left pixel in the range.
   * @param y  the y-coordinate of the top left pixel in the range.
   * @param w  the width of the pixel range.
   * @param h  the height of the pixel range.
   * @param edgeOp  indicates how to determine the values for the range
   *     (either {@link #EDGE_ZERO_FILL} or {@link #EDGE_NO_OP}).
   */
  private void fillEdge(Raster src, WritableRaster dest, int x, int y, int w, 
                        int h, int edgeOp) 
  {
    if (w <= 0)
      return;
    if (h <= 0)
      return;
    if (edgeOp == EDGE_ZERO_FILL)  // fill region with zeroes
      {
        float[] zeros = new float[src.getNumBands() * w * h];
        dest.setPixels(x, y, w, h, zeros); 
      }
    else  // copy pixels from source
      {
        float[] pixels = new float[src.getNumBands() * w * h];
        src.getPixels(x, y, w, h, pixels);
        dest.setPixels(x, y, w, h, pixels);
      }
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#createCompatibleDestRaster(java.awt.image.Raster)
   */
  public WritableRaster createCompatibleDestRaster(Raster src)
  {
    return src.createCompatibleWritableRaster();
  }

  /* (non-Javadoc)
   * @see java.awt.image.BufferedImageOp#getBounds2D(java.awt.image.BufferedImage)
   */
  public final Rectangle2D getBounds2D(BufferedImage src)
  {
    return src.getRaster().getBounds();
  }

  /* (non-Javadoc)
   * @see java.awt.image.RasterOp#getBounds2D(java.awt.image.Raster)
   */
  public final Rectangle2D getBounds2D(Raster src)
  {
    return src.getBounds();
  }

  /**
   * Returns the corresponding destination point for a source point. Because
   * this is not a geometric operation, the destination and source points will
   * be identical.
   * 
   * @param src The source point.
   * @param dst The transformed destination point.
   * @return The transformed destination point.
   */
  public final Point2D getPoint2D(Point2D src, Point2D dst)
  {
    if (dst == null) return (Point2D)src.clone();
    dst.setLocation(src);
    return dst;
  }
}