chunk_plte.java

Mapserver的一个java客户端,包含两个applet支持地图显示。

// Copyright (C) 1998, 1999, 2001 Chris Nokleberg
// Please see included LICENSE.TXT

package com.sixlegs.image.png;

import java.awt.image.IndexColorModel;
import java.io.IOException;

final class Chunk_PLTE
extends Chunk
{
    private int size;

    /* package */ int[] r_raw;
    /* package */ int[] g_raw;
    /* package */ int[] b_raw;
    /* package */ int[] a_raw;

    /* package */ byte[] r;
    /* package */ byte[] g;
    /* package */ byte[] b;
    /* package */ byte[] a;

    Chunk_PLTE()
    {
        super(PLTE);
    }

    protected boolean multipleOK()
    {
        return false;
    }

    protected boolean beforeIDAT()
    {
        return true;
    }

    protected void readData()
    throws IOException
    {
        img.data.palette = this;
        if (img.getChunk(bKGD) != null) {
            throw new PngException("bKGD chunk must follow PLTE chunk");
        }
        if (!img.data.header.colorUsed) {
            throw new PngExceptionSoft("PLTE chunk found in grayscale image");
        }
        if (length % 3 != 0) {
            throw new PngException("PLTE chunk length indivisible by 3");
        }
        size = length / 3;

        /// look into this
        if (img.data.header.colorType == PngImage.COLOR_TYPE_PALETTE) {
            if (size > (2 << img.data.header.depth)) {
                throw new PngException("Too many palette entries");
            } else if (size > 256) {
                throw new PngExceptionSoft("Too many palette entries");
            }
        }

        r = new byte[size];
        g = new byte[size];
        b = new byte[size];

        int[][] raw  = new int[3][size];
        r_raw = raw[0];
        g_raw = raw[1];
        b_raw = raw[2];

        for (int i = 0; i < size; i++) {
            r_raw[i] = in_data.readUnsignedByte();
            g_raw[i] = in_data.readUnsignedByte();
            b_raw[i] = in_data.readUnsignedByte();
        }

        updateProperties(false);
    }

    // TODO: stop duplication of palette data?
    /* package */ void updateProperties(boolean alpha)
    {
        int[][] prop = new int[alpha ? 4 : 3][size];
        System.arraycopy(r_raw, 0, prop[0], 0, size);
        System.arraycopy(g_raw, 0, prop[1], 0, size);
        System.arraycopy(b_raw, 0, prop[2], 0, size);
        if (alpha) {
            System.arraycopy(a_raw, 0, prop[3], 0, size);
        }
        img.data.properties.put("palette", prop);
        img.data.properties.put("palette size", new Integer(size));
    }

    /* package */ void calculate()
    {
        for (int i = 0; i < size; i++) {
            r[i] = (byte)img.data.gammaTable[r_raw[i]];
            g[i] = (byte)img.data.gammaTable[g_raw[i]];
            b[i] = (byte)img.data.gammaTable[b_raw[i]];
        }
        if (img.data.header.paletteUsed) {
            if (a != null) {
                img.data.header.model = 
                    new IndexColorModel(img.data.header.cmBits, size, r, g, b, a);
            } else {
                img.data.header.model = 
                    new IndexColorModel(img.data.header.cmBits, size, r, g, b);
            }
        }
    }
}