rescaleop.java

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/*
 * @(#)RescaleOp.java	1.42 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.awt.image;

import java.awt.color.ColorSpace;
import java.awt.geom.Rectangle2D;
import java.awt.Rectangle;
import java.awt.geom.Point2D;
import java.awt.RenderingHints;
import sun.awt.image.ImagingLib;

/**
 * This class performs a pixel-by-pixel rescaling of the data in the
 * source image by multiplying the sample values for each pixel by a scale
 * factor and then adding an offset. The scaled sample values are clipped
 * to the minimum/maximum representable in the destination image.
 * <p>
 * The pseudo code for the rescaling operation is as follows:
 * <pre>
 *for each pixel from Source object {
 *    for each band/component of the pixel {
 *        dstElement = (srcElement*scaleFactor) + offset
 *    }
 *}
 * </pre>
 * <p>
 * For Rasters, rescaling operates on bands.  The number of
 * sets of scaling constants may be one, in which case the same constants
 * are applied to all bands, or it must equal the number of Source
 * Raster bands.
 * <p>
 * For BufferedImages, rescaling operates on color and alpha components.
 * The number of sets of scaling constants may be one, in which case the
 * same constants are applied to all color (but not alpha) components.
 * Otherwise, the  number of sets of scaling constants may
 * equal the number of Source color components, in which case no
 * rescaling of the alpha component (if present) is performed.
 * If neither of these cases apply, the number of sets of scaling constants
 * must equal the number of Source color components plus alpha components,
 * in which case all color and alpha components are rescaled.
 * <p>
 * BufferedImage sources with premultiplied alpha data are treated in the same
 * manner as non-premultiplied images for purposes of rescaling.  That is,
 * the rescaling is done per band on the raw data of the BufferedImage source
 * without regard to whether the data is premultiplied.  If a color conversion
 * is required to the destination ColorModel, the premultiplied state of
 * both source and destination will be taken into account for this step.
 * <p>
 * Images with an IndexColorModel cannot be rescaled.
 * <p>
 * If a RenderingHints object is specified in the constructor, the
 * color rendering hint and the dithering hint may be used when color
 * conversion is required.
 * <p>
 * Note that in-place operation is allowed (i.e. the source and destination can
 * be the same object).
 * @version 10 Feb 1997
 * @see java.awt.RenderingHints#KEY_COLOR_RENDERING
 * @see java.awt.RenderingHints#KEY_DITHERING
 */
public class RescaleOp implements BufferedImageOp, RasterOp {
    float[] scaleFactors;
    float[] offsets;
    int length = 0;
    RenderingHints hints;

    private int srcNbits;
    private int dstNbits;

    
    /**
     * Constructs a new RescaleOp with the desired scale factors
     * and offsets.  The length of the scaleFactor and offset arrays
     * must meet the restrictions stated in the class comments above.
     * The RenderingHints argument may be null.
     * @param scaleFactors the specified scale factors
     * @param offsets the specified offsets
     * @param hints the specified <code>RenderingHints</code>, or
     *        <code>null</code>
     */
    public RescaleOp (float[] scaleFactors, float[] offsets,
                      RenderingHints hints) {
        length = scaleFactors.length;
        if (length > offsets.length) length = offsets.length;

        this.scaleFactors = new float[length];
        this.offsets      = new float[length];
        for (int i=0; i < length; i++) {
            this.scaleFactors[i] = scaleFactors[i];
            this.offsets[i]      = offsets[i];
        }
        this.hints = hints;
    }

    /**
     * Constructs a new RescaleOp with the desired scale factor
     * and offset.  The scaleFactor and offset will be applied to
     * all bands in a source Raster and to all color (but not alpha)
     * components in a BufferedImage.
     * The RenderingHints argument may be null.
     * @param scaleFactor the specified scale factor
     * @param offset the specified offset
     * @param hints the specified <code>RenderingHints</code>, or
     *        <code>null</code>
     */
    public RescaleOp (float scaleFactor, float offset, RenderingHints hints) {
        length = 1;
        this.scaleFactors = new float[1];
        this.offsets      = new float[1];
        this.scaleFactors[0] = scaleFactor;
        this.offsets[0]       = offset;
        this.hints = hints;
    }

    /** 
     * Returns the scale factors in the given array. The array is also
     * returned for convenience.  If scaleFactors is null, a new array
     * will be allocated.
     * @param scaleFactors the array to contain the scale factors of 
     *        this <code>RescaleOp</code>
     * @return the scale factors of this <code>RescaleOp</code>.
     */
    final public float[] getScaleFactors (float scaleFactors[]) {
        if (scaleFactors == null) {
            return (float[]) this.scaleFactors.clone();
        }
        System.arraycopy (this.scaleFactors, 0, scaleFactors, 0,
                          Math.min(this.scaleFactors.length,
                                   scaleFactors.length));
        return scaleFactors;
    }

    /**
     * Returns the offsets in the given array. The array is also returned
     * for convenience.  If offsets is null, a new array
     * will be allocated.
     * @param offsets the array to contain the offsets of 
     *        this <code>RescaleOp</code>
     * @return the offsets of this <code>RescaleOp</code>.
     */
    final public float[] getOffsets(float offsets[]) {
        if (offsets == null) {
            return (float[]) this.offsets.clone();
        }

        System.arraycopy (this.offsets, 0, offsets, 0, 
                          Math.min(this.offsets.length, offsets.length));
        return offsets;
    }

    /**
     * Returns the number of scaling factors and offsets used in this
     * RescaleOp.
     * @return the number of scaling factors and offsets of this 
     *         <code>RescaleOp</code>.
     */
    final public int getNumFactors() {
        return length;
    }
     

    /**
     * Creates a ByteLookupTable to implement the rescale.
     * The table may have either a SHORT or BYTE input.
     * @param nElems    Number of elements the table is to have.
     *                  This will generally be 256 for byte and
     *                  65536 for short.
     */
    private ByteLookupTable createByteLut(float scale[],
                                          float off[],
                                          int   nBands,
                                          int   nElems) {
 
        byte[][]        lutData = new byte[scale.length][nElems];
 
        for (int band=0; band<scale.length; band++) {
            float  bandScale   = scale[band];
            float  bandOff     = off[band];
            byte[] bandLutData = lutData[band];
            for (int i=0; i<nElems; i++) {
                int val = (int)(i*bandScale + bandOff);
                if ((val & 0xffffff00) != 0) {
                    if (val < 0) {
                        val = 0;
                    } else {
                        val = 255;
                    } 
                }
                bandLutData[i] = (byte)val;
            }

        }
 
        return new ByteLookupTable(0, lutData);
    }
 
    /**
     * Creates a ShortLookupTable to implement the rescale.
     * The table may have either a SHORT or BYTE input.
     * @param nElems    Number of elements the table is to have.
     *                  This will generally be 256 for byte and
     *                  65536 for short.
     */
    private ShortLookupTable createShortLut(float scale[],
                                            float off[],
                                            int   nBands,
                                            int   nElems) {
 
        short[][]        lutData = new short[scale.length][nElems];
 
        for (int band=0; band<scale.length; band++) {
            float   bandScale   = scale[band];
            float   bandOff     = off[band];
            short[] bandLutData = lutData[band];
            for (int i=0; i<nElems; i++) {
                int val = (int)(i*bandScale + bandOff);
                if ((val & 0xffff0000) != 0) {
                    if (val < 0) {
                        val = 0;
                    } else {
                        val = 65535;
                    }
                }
                bandLutData[i] = (short)val;
            }
        }
 
        return new ShortLookupTable(0, lutData);
    }
 
 
    /**
     * Determines if the rescale can be performed as a lookup.
     * The dst must be a byte or short type.
     * The src must be less than 16 bits.
     * All source band sizes must be the same and all dst band sizes
     * must be the same.
     */
    private boolean canUseLookup(Raster src, Raster dst) {

        //
        // Check that the src datatype is either a BYTE or SHORT
        //
        int datatype = src.getDataBuffer().getDataType();
        if(datatype != DataBuffer.TYPE_BYTE &&
           datatype != DataBuffer.TYPE_USHORT) {
            return false;
        }
 
        //
        // Check dst sample sizes. All must be 8 or 16 bits.
        //
        SampleModel dstSM = dst.getSampleModel();
        dstNbits = dstSM.getSampleSize(0);

        if (!(dstNbits == 8 || dstNbits == 16)) {
            return false;
        }
        for (int i=1; i<src.getNumBands(); i++) {
            int bandSize = dstSM.getSampleSize(i);
            if (bandSize != dstNbits) {
                return false;
            }
        }
 
        //
        // Check src sample sizes. All must be the same size 
        //
        SampleModel srcSM = src.getSampleModel();
        srcNbits = srcSM.getSampleSize(0);
        if (srcNbits > 16) {
            return false;
        }
        for (int i=1; i<src.getNumBands(); i++) {
            int bandSize = srcSM.getSampleSize(i);
            if (bandSize != srcNbits) {
                return false;
            }
        }
 
        return true;
    }
 
    /**
     * Rescales the source BufferedImage.  
     * If the color model in the source image is not the same as that
     * in the destination image, the pixels will be converted
     * in the destination.  If the destination image is null,
     * a BufferedImage will be created with the source ColorModel.
     * An IllegalArgumentException may be thrown if the number of
     * scaling factors/offsets in this object does not meet the
     * restrictions stated in the class comments above, or if the
     * source image has an IndexColorModel.
     * @param src the <code>BufferedImage</code> to be filtered
     * @param dst the destination for the filtering operation 
     *            or <code>null</code>
     * @return the filtered <code>BufferedImage</code>.
     * @throws IllegalArgumentException if the <code>ColorModel</code>
     *         of <code>src</code> is an <code>IndexColorModel</code>,  
     *         or if the number of scaling factors and offsets in this
     *         <code>RescaleOp</code> do not meet the requirements 
     *         stated in the class comments.
     */
    public final BufferedImage filter (BufferedImage src, BufferedImage dst) {
        ColorModel srcCM = src.getColorModel();
        ColorModel dstCM;
        int numBands = srcCM.getNumColorComponents();

        
        if (srcCM instanceof IndexColorModel) {
            throw new
                IllegalArgumentException("Rescaling cannot be "+
                                         "performed on an indexed image");
        }
        if (length != 1 && length != numBands &&
            length != srcCM.getNumComponents())
        {
            throw new IllegalArgumentException("Number of scaling constants "+
                                               "does not equal the number of"+
                                               " of color or color/alpha "+