poi/src/java/org/apache/poi/hssf/usermodel/HSSFPalette.java

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package org.apache.poi.hssf.usermodel;

import org.apache.poi.hssf.record.PaletteRecord;
import org.apache.poi.hssf.util.HSSFColor;

/**
 * Represents a workbook color palette.
 * Internally, the XLS format refers to colors using an offset into the palette
 * record.  Thus, the first color in the palette has the index 0x8, the second
 * has the index 0x9, etc. through 0x40
 *
 * @author Brian Sanders (bsanders at risklabs dot com)
 */
public class HSSFPalette
{
    private PaletteRecord palette;
    
    protected HSSFPalette(PaletteRecord palette)
    {
        this.palette = palette;
    }
    
    /**
     * Retrieves the color at a given index
     *
     * @param index the palette index, between 0x8 to 0x40 inclusive
     * @return the color, or null if the index is not populated
     */
    public HSSFColor getColor(short index)
    {
        byte[] b = palette.getColor(index);
        if (b != null)
        {
            return new CustomColor(index, b);
        }
        return null;
    }
    
    /**
     * Finds the first occurance of a given color
     *
     * @param red the RGB red component, between 0 and 255 inclusive
     * @param green the RGB green component, between 0 and 255 inclusive
     * @param blue the RGB blue component, between 0 and 255 inclusive
     * @return the color, or null if the color does not exist in this palette
     */
    public HSSFColor findColor(byte red, byte green, byte blue)
    {
        byte[] b = palette.getColor(PaletteRecord.FIRST_COLOR_INDEX);
        for (short i = (short) PaletteRecord.FIRST_COLOR_INDEX; b != null;
            b = palette.getColor(++i))
        {
            if (b[0] == red && b[1] == green && b[2] == blue)
            {
                return new CustomColor(i, b);
            }
        }
        return null;
    }
    
    /**
     * Sets the color at the given offset
     *
     * @param index the palette index, between 0x8 to 0x40 inclusive
     * @param red the RGB red component, between 0 and 255 inclusive
     * @param green the RGB green component, between 0 and 255 inclusive
     * @param blue the RGB blue component, between 0 and 255 inclusive
     */
    public void setColorAtIndex(short index, byte red, byte green, byte blue)
    {
        palette.setColor(index, red, green, blue);
    }
    
    private static class CustomColor extends HSSFColor
    {
        private short byteOffset;
        private byte red;
        private byte green;
        private byte blue;
        
        private CustomColor(short byteOffset, byte[] colors)
        {
            this(byteOffset, colors[0], colors[1], colors[2]);
        }
        
        private CustomColor(short byteOffset, byte red, byte green, byte blue)
        {
            this.byteOffset = byteOffset;
            this.red = red;
            this.green = green;
            this.blue = blue;
        }
        
        public short getIndex()
        {
            return byteOffset;
        }
        
        public short[] getTriplet()
        {
            return new short[]
            {
                (short) (red   & 0xff),
                (short) (green & 0xff),
                (short) (blue  & 0xff)
            };
        }
        
        public String getHexString()
        {
            StringBuffer sb = new StringBuffer();
            sb.append(getGnumericPart(red));
            sb.append(':');
            sb.append(getGnumericPart(green));
            sb.append(':');
            sb.append(getGnumericPart(blue));
            return sb.toString();
        }
        
        private String getGnumericPart(byte color)
        {
            String s;
            if (color == 0)
            {
                s = "0";
            }
            else
            {
                int c = color & 0xff; //as unsigned
                c = (c << 8) | c; //pad to 16-bit
                s = Integer.toHexString(c).toUpperCase();
                while (s.length() < 4)
                {
                    s = "0" + s;
                }
            }
            return s;
        }
    }
}