图片转为byte[]、String、图片之间的转换

package com.horizon.action;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

import javax.imageio.stream.FileImageInputStream;
import javax.imageio.stream.FileImageOutputStream;

public class Hello {
    // 图片到byte数组
    public byte[] image2byte(String path) {
        byte[] data = null;
        FileImageInputStream input = null;
        try {
            input = new FileImageInputStream(new File(path));
            ByteArrayOutputStream output = new ByteArrayOutputStream();
            byte[] buf = new byte[1024];
            int numBytesRead = 0;
            while ((numBytesRead = input.read(buf)) != -1) {
                output.write(buf, 0, numBytesRead);
            }
            data = output.toByteArray();
            output.close();
            input.close();
        } catch (FileNotFoundException ex1) {
            ex1.printStackTrace();
        } catch (IOException ex1) {
            ex1.printStackTrace();
        }
        return data;
    }

    // byte数组到图片
    public void byte2image(byte[] data, String path) {
        if (data.length < 3 || path.equals(""))
            return;
        try {
            FileImageOutputStream imageOutput = new FileImageOutputStream(
                    new File(path));
            imageOutput.write(data, 0, data.length);
            imageOutput.close();
            System.out.println("Make Picture success,Please find image in "
                    + path);
        } catch (Exception ex) {
            System.out.println("Exception: " + ex);
            ex.printStackTrace();
        }
    }

    /**
     * Convert byte[] to hex
     * string.这里我们可以将byte转换成int，然后利用Integer.toHexString(int)来转换成16进制字符串。
     * 
     * @param src
     *            byte[] data
     * @return hex string
     */
    public static String bytesToHexString(byte[] src) {
        StringBuilder stringBuilder = new StringBuilder("");
        if (src == null || src.length <= 0) {
            return null;
        }
        for (int i = 0; i < src.length; i++) {
            int v = src[i] & 0xFF;
            String hv = Integer.toHexString(v);
            if (hv.length() < 2) {
                stringBuilder.append(0);
            }
            stringBuilder.append(hv);
        }
        return stringBuilder.toString();
    }

    /**
     * Convert hex string to byte[]
     * 
     * @param hexString
     *            the hex string
     * @return byte[]
     */
    public static byte[] hexStringToBytes(String hexString) {
        if (hexString == null || hexString.equals("")) {
            return null;
        }
        hexString = hexString.toUpperCase();
        int length = hexString.length() / 2;
        char[] hexChars = hexString.toCharArray();
        byte[] d = new byte[length];
        for (int i = 0; i < length; i++) {
            int pos = i * 2;
            d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));
        }
        return d;
    }

    /**
     * Convert char to byte
     * 
     * @param c
     *            char
     * @return byte
     */
    private static byte charToByte(char c) {
        return (byte) "0123456789ABCDEF".indexOf(c);
    }

    @SuppressWarnings("static-access")
    public static void main(String[] args) {
        String fromPath = "C:/Users/Administrator/123.jpg";
        String toPath = "C:/Users/Administrator/456.jpg";
        Hello hello = new Hello();
        byte[] bytes = hello.image2byte(fromPath);
        String hexString = hello.bytesToHexString(bytes);
        byte[] bytes2 = hello.hexStringToBytes(hexString);
        hello.byte2image(bytes2, toPath);
    }
}