从位图解码

/*

 * Syncany, www.syncany.org

 * Copyright (C) 2011 Philipp C. Heckel <philipp.heckel@gmail.com> 

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

//package com.nowjava;

import java.io.File;
/* from 
时代Java公众号 - nowjava.com*/

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.InputStream;

import java.io.OutputStream;


public class Main {

    public static void main(String[] argv) throws Exception {

        File srcFile = new File("Main.java");

        File dstFile = new File("Main.java");

        decodeFromBitmap(srcFile, dstFile);
        /**
         * 时 代 J a v a 公 众 号 - nowjava.com 提 供 
        **/

    }


    private static final int BMP_OFFSET_IMAGE_WIDTH = 18;


    public static void decodeFromBitmap(File srcFile, File dstFile)

            throws Exception {

        // NOTE: For some reason, decoding from a non-FileInputStream does not

        //       always work properly. Do not create a method 

        //       decodeFromBitmap(InputStream, ...)


        InputStream is = new FileInputStream(srcFile);


        // Read BMP width from header

        is.skip(BMP_OFFSET_IMAGE_WIDTH);


        byte[] imageWidthBytes = new byte[4];

        is.read(imageWidthBytes);

        int imageWidth = toIntLE(imageWidthBytes);


        // Row length must be divisible by 4; calculate padding

        int linePadding = 4 - (imageWidth * 3 % 4);


        // Skip to the 'horizontal resolution' field

        is.skip(16);

        byte[] payloadLengthBytes = new byte[4];

        is.read(payloadLengthBytes);

        int payloadLength = toIntLE(payloadLengthBytes);


        is.skip(12);//BMP_HEADER_LENGTH - OFFSET_IMAGE_WIDTH - 4);   


        OutputStream os = new FileOutputStream(dstFile);


        byte[] row = new byte[imageWidth * 3];

        int read;

        int restOfPayload = payloadLength;


        while ((read = is.read(row)) != -1) {

            if (restOfPayload >= read) {

                os.write(