Base64 image

2022-09-30 09:00:38

【前端攻略】：玩转图片Base64编码

什么是 base64 编码?　　

我不是来讲概念的，直接切入正题，图片的 base64 编码就是可以将一副图片数据编码成一串字符串，使用该字符串代替图像地址。

这样做有什么意义呢？我们知道，我们所看到的网页上的每一个图片，都是需要消耗一个 http 请求下载而来的（所有才有了 csssprites 技术的应运而生，但是 csssprites 有自身的局限性，下文会提到）。

没错，不管如何，图片的下载始终都要向服务器发出请求，要是图片的下载不用向服务器发出请求，而可以随着 HTML 的下载同时下载到本地那就太好了，而 base64 正好能解决这个问题。

http://www.cnblogs.com/coco1s/p/4375774.html

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

在html中的使用

<img src='data:image/gif;base64,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'/> <br />

效果：

Base64 image

法1：

        ByteArrayOutputStream output = new ByteArrayOutputStream();

        RenderedImage image = producer.createImage(imageCode);

        ImageIO.write(image, "PNG", output);

        return DatatypeConverter.printBase64Binary(output.toByteArray());

法2：

import org.apache.commons.codec.binary.Base64;

import org.apache.commons.imaging.*;

import org.apache.commons.io.FileUtils;

import java.awt.*;

import java.awt.image.BufferedImage;

import java.io.File;

import java.io.IOException;

import java.util.HashMap;

import java.util.Map;

public class Base64Image {

    public static String getBase64(String path) throws IOException {

        byte[] bytes = FileUtils.readFileToByteArray(new File(path));

        String base64String = Base64.encodeBase64String(bytes);

        return base64String;

    }

    public static void getImage(String base64,String outPath) throws IOException, ImageReadException, ImageWriteException {

        if (base64!=null&&!"".equals(base64)){

            int i = base64.lastIndexOf(",");

            if (i>=0){

                base64=base64.substring(i+1);

            }

            byte[] bytes = Base64.decodeBase64(base64);

            BufferedImage bufferedImage = Imaging.getBufferedImage(bytes);

            Map<String, Object> params = new HashMap<String,Object>();

            Imaging.writeImage(bufferedImage,new File(outPath), ImageFormats.BMP, params);

        }

    }

}

https://github.com/xuejike/Base64Image/blob/6b31d9931019184f0efcc6e3d9009f0d94d374ee/src/main/java/com/bidanet/image/Base64Image.java

法3
II. Java 8 Encode an Image to Base64

public static String encoder(String imagePath) {

    String base64Image = "";

    File file = new File(imagePath);

    try (FileInputStream imageInFile = new FileInputStream(file)) {

        // Reading a Image file from file system

        byte imageData[] = new byte[(int) file.length()];

        imageInFile.read(imageData);

        base64Image = Base64.getEncoder().encodeToString(imageData);

    } catch (FileNotFoundException e) {

        System.out.println("Image not found" + e);

    } catch (IOException ioe) {

        System.out.println("Exception while reading the Image " + ioe);

    }

    return base64Image;

}

III. Java 8 Decode an Base64 String to an Image

public static void decoder(String base64Image, String pathFile) {

    try (FileOutputStream imageOutFile = new FileOutputStream(pathFile)) {

        // Converting a Base64 String into Image byte array

        byte[] imageByteArray = Base64.getDecoder().decode(base64Image);

        imageOutFile.write(imageByteArray);

    } catch (FileNotFoundException e) {

        System.out.println("Image not found" + e);

    } catch (IOException ioe) {

        System.out.println("Exception while reading the Image " + ioe);

    }

}

http://javasampleapproach.com/java/java-advanced/java-8-encode-decode-an-image-base64

http://javasampleapproach.com/java-integration/transfer-image-restfulapi-image-restfulapi
convert image to base64 with java
https://*.com/questions/28268511/convert-image-to-base64-with-java

页面以base64输出图片http://www.cnblogs.com/LittleMing/p/4882366.html

JavaWeb: 搞定验证码
http://www.jianshu.com/p/9284a31e6ce8

import sun.misc.BASE64Decoder;

import sun.misc.BASE64Encoder;

import javax.imageio.ImageIO;

import javax.imageio.stream.FileImageOutputStream;

import java.awt.*;

import java.awt.image.BufferedImage;

import java.io.*;

import java.util.Random;

/**

 * 生成随机数字或字母串，以图像方式显示，用于人工识别，使程序很难识别。

 * 减小系统被程序自动攻击的可能性。

 * 生成的图形颜色由红、黑、蓝、紫4中随机组合而成，数字或字母垂直方向位置在

 * 一定范围内也是随机的，减少被程序自动识别的几率。

 * 由于数字的0，1，2易和字母的o，l,z混淆，使人眼难以识别，因此不生成数字和字母的混合串。

 * 生成的串字母统一用小写，串的最大长度为16。

 *

 */

public class RandomGraphic {

//字符的高度和宽度，单位为像素

    private int wordHeight = 10;

    private int wordWidth = 15;

//字符大小

    private int fontSize = 16;

//最大字符串个数

    private  static final int MAX_CHARCOUNT = 16;

//垂直方向起始位置

    private final int initypos = 5;

//要生成的字符个数，由工厂方法得到

    private int charCount = 0;

//颜色数组，绘制字串时随机选择一个

    private static final Color[] CHAR_COLOR = {Color.RED,Color.BLUE,Color.MAGENTA,Color.blue};

//随机数生成器

    private Random r = new Random();

    /**

     * 生成图像的格式常量，JPEG格式,生成为文件时扩展名为.jpg；

     * 输出到页面时需要设置MIME type 为image/jpeg

     */

    public static String GRAPHIC_JPEG = "JPEG";

    /**

     * 生成图像的格式常量，PNG格式,生成为文件时扩展名为.png；

     * 输出到页面时需要设置MIME type 为image/png

     */

    public static String GRAPHIC_PNG = "PNG";

//用工厂方法创建对象

    protected RandomGraphic(int charCount){

        this.charCount = charCount;

    }

    /**

     * 创建对象的工厂方法

     * @param charCount 要生成的字符个数，个数在1到16之间

     * @return 返回RandomGraphic对象实例

     * @throws Exception 参数charCount错误时抛出

     */

    public static RandomGraphic createInstance(int charCount) throws Exception{

        if (charCount < 1 || charCount > MAX_CHARCOUNT){

            throw new Exception("Invalid parameter charCount,charCount should between in 1 and 16");

        }

        return new RandomGraphic(charCount);

    }

    /**

     *  随机生成一个数字串，并以图像方式绘制，绘制结果输出到流out中

     * @param graphicFormat 设置生成的图像格式，值为GRAPHIC_JPEG或GRAPHIC_PNG

     * @param out 图像结果输出流

     * @return 随机生成的串的值

     * @throws IOException

     */

    public String drawNumber(String graphicFormat,OutputStream out) throws IOException{

// 随机生成的串的值

        String charValue = "";

        /*charValue = randNumber();*/

        charValue = randAlphaStr(4);

        return draw(charValue,graphicFormat,out);

    }

    /**

     * 随机生成一个字母串，并以图像方式绘制，绘制结果输出到流out中

     * @param graphicFormat 设置生成的图像格式，值为GRAPHIC_JPEG或GRAPHIC_PNG

     * @param out 图像结果输出流

     * @return 随机生成的串的值

     * @throws IOException

     */

    public String drawAlpha(String graphicFormat,OutputStream out) throws IOException{

//  随机生成的串的值

        String charValue = "";

        charValue = randAlphaStr(4);

        return draw(charValue,graphicFormat,out);

    }

    // 给定范围获得随机颜色

    Color getRandColor(int fc, int bc) {

        Random random = new Random();

        if (fc > 255) {

            fc = 255;

        }

        if (bc > 255) {

            bc = 255;

        }

        int r = fc + random.nextInt(bc - fc);

        int g = fc + random.nextInt(bc - fc);

        int b = fc + random.nextInt(bc - fc);

        return new Color(r, g, b);

    }

    /**

     * 以图像方式绘制字符串，绘制结果输出到流out中

     * @param charValue 要绘制的字符串

     * @param graphicFormat 设置生成的图像格式，值为GRAPHIC_JPEG或GRAPHIC_PNG

     * @param out 图像结果输出流

     * @return 随机生成的串的值

     * @throws IOException

     */

    protected String draw(String charValue,String graphicFormat,OutputStream out) throws IOException{

        int width = (charCount+2) * wordWidth;

        int height = wordHeight * 3;

        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        // 创建一个随机数生成器类。

        Random random = new Random();

        // 获取图形上下文

        Graphics g = image.getGraphics();

        // 设定背景色

        g.setColor(getColor(100));

        g.fillRect(0, 0, width, height);

        // 设定字体

        g.setFont(new Font("宋体", Font.BOLD, 18));

        // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到

        g.setColor(getRandColor(160, 200));

        for (int i = 0; i < 155; i++) {

            int x = random.nextInt(width);

            int y = random.nextInt(height);

            int xl = random.nextInt(12);

            int yl = random.nextInt(12);

            g.setColor(getColor(25));

            g.drawLine(x, y, x + xl, y + yl);

        }

        // 绘制charValue,每个字符颜色随机

        for(int i = 0; i < charCount; i++){

            String c = charValue.substring(i,i+1);

            Color color =  CHAR_COLOR[randomInt(0,CHAR_COLOR.length)];

            g.setColor(color);

            int xpos = (i+1) * wordWidth;

            // 垂直方向上随机

            int ypos = randomInt(initypos+wordHeight,initypos+wordHeight*2);

            g.drawString(c,xpos,ypos);

        }

        g.dispose();

        image.flush();

        // 输出到流

        ImageIO.write(image,graphicFormat,out);

        return charValue;

    }

    /*** 随机返回一种颜色,透明度0~255 0表示全透

     * @return 随机返回一种颜色

     * @param alpha 透明度0~255 0表示全透

     */

    private Color getColor(int alpha)

    {

        int R=(int) (Math.random()*255);

        int G=(int) (Math.random()*255);

        int B=(int) (Math.random()*255);

        return new Color(R,G,B,alpha);

    }

    public String drawInputstr(int num,String graphicFormat,OutputStream out) throws IOException{

        String charValue = randAlphaStr(num);

        int width = (charCount+2) * wordWidth;

        int height = wordHeight * 3;

        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        ByteArrayOutputStream byteOut = new ByteArrayOutputStream();

        // 创建一个随机数生成器类。

        Random random = new Random();

        // 获取图形上下文

        Graphics g = image.getGraphics();

        // 设定背景色

        g.setColor(getColor(80));

        g.fillRect(0, 0, width, height);

        //设置干扰点

        CreateRandomPoint(width, height,50,g,255);

        // 设定字体

        g.setFont(new Font("宋体", Font.BOLD, 18));

        // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到

        g.setColor(getRandColor(160, 200));

        for (int i = 0; i < 135; i++) {

            int x = random.nextInt(width);

            int y = random.nextInt(height);

            int xl = random.nextInt(12);

            int yl = random.nextInt(12);

            g.setColor(getColor(200));

            g.drawLine(x, y, x + xl, y + yl);

        }

        // 绘制charValue,每个字符颜色随机

        for(int i = 0; i < charCount; i++){

            String c = charValue.substring(i,i+1);

            Color color =  CHAR_COLOR[randomInt(0,CHAR_COLOR.length)];

            g.setColor(color);

            int xpos = (i+1) * wordWidth;

            // 垂直方向上随机

            int ypos = randomInt(initypos+wordHeight,initypos+wordHeight*2);

            g.drawString(c,xpos,ypos);

        }

        g.dispose();

        image.flush();

        // 输出到流

        ImageIO.write( image, graphicFormat, out);

        return charValue;

    }

// 生成随机数字串

    protected String randNumber(){

        String charValue = "";

        for (int i = 0; i < charCount; i++){

            charValue += String.valueOf(randomInt(0,10));

        }

        return charValue;

    }

// 生成随机字母串

    private String randAlpha(){

        String charValue = "";

        for (int i = 0; i < charCount; i++){

            char c = (char) (randomInt(0,26)+'a');

            charValue += String.valueOf(c);

        }

        return charValue;

    }

// 生成随机字符串

    private String randAlphaStr(int num){

        StringBuffer charValue = new StringBuffer();

        String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";

        Random random=new Random();

        StringBuffer sb=new StringBuffer();

        for(int i=0;i<num;i++){

            int number=random.nextInt(62);

            charValue.append(str.charAt(number));

        }

        return charValue.toString();

    }

    /**

     * 返回[from,to)之间的一个随机整数

     * @param from 起始值

     * @param to 结束值

     * @return [from,to)之间的一个随机整数

     */

    protected int randomInt(int from,int to){

        return from+r.nextInt(to-from);

    }

    /**

     * 随机产生干扰点

     * @param width

     * @param height

     * @param many

     * @param g

     * @param alpha 透明度0~255 0表示全透

     */

    private void CreateRandomPoint(int width,int height,int many,Graphics g,int alpha)

    {  // 随机产生干扰点

        Random random = new Random();

        for (int i=0;i<many;i++) {

            int x = random.nextInt(width);

            int y = random.nextInt(height);

            g.setColor(getColor(alpha));

            g.drawOval(x,y,random.nextInt(3),random.nextInt(3));

        }

    }

    public static void main(String[] args) throws FileNotFoundException, IOException, Exception {

// TODO Auto-generated method stub

        ByteArrayOutputStream output = new ByteArrayOutputStream();

        String str = RandomGraphic.createInstance(4).drawInputstr(4,RandomGraphic.GRAPHIC_PNG,output);

        System.out.println("----------------str:"+str);

        byte[] captcha = output.toByteArray();

        BASE64Encoder encoder = new BASE64Encoder();

        String imagestr =  encoder.encode(captcha);// 返回Base64编码过的字节数组字符串

        System.out.println("----------------:"+imagestr);

        System.out.println("----------------:"+captcha.toString());

        String path = "D:/myimg.png";

        String path2 = "D:/myimg2.png";

        byte[] data = captcha;

        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();

        }

        BASE64Decoder decoder = new BASE64Decoder();

        try {

            // Base64解码

            byte[] bytes = decoder.decodeBuffer(imagestr);

            for (int i = 0; i < bytes.length; ++i) {

                if (bytes[i] < 0) {// 调整异常数据

                    bytes[i] += 256;

                }

            }

            // 生成jpeg图片

            OutputStream out = new FileOutputStream(path2);

            out.write(bytes);

            out.flush();

            out.close();

        } catch (Exception e) {

        }

      //

       // System.out.println(RandomGraphic.createInstance(4).drawAlpha(RandomGraphic.GRAPHIC_JPEG,new FileOutputStream("D:/myimg2.png")));

    }

上一篇介绍中，我们将二进制文件(BLOB)保存为Base64编码的文本，这些文本可以内嵌在XML的标签中，因此二进制信息它可以随着XML文件被拷贝、下载而不用担心信息会缺失。这项技术也在email邮件中被广泛使用。

浏览器对Base64的支持
图像是最经常被使用的一种二进制文件。而现代的浏览器的进步日新月异，IE7，FireFox和其他浏览器为包括Base64在内各种编码的图像信息提供了很好的支持。因此图形信息可以以下面的形式呈现在页面中、

<img src="data:image/gif;base64,R0lGODlhDwAPAKECAAAAzMzM/////
wAAACwAAAAADwAPAAACIISPeQHsrZ5ModrLlN48CXF8m2iQ3YmmKqVlRtW4ML
wWACH+H09wdGltaXplZCBieSBVbGVhZCBTbWFydFNhdmVyIQAAOw=="
alt="Base64 encoded image" width="150" height="150"/>

这种data: URI的格式能把Base64（或其他数据）可以内嵌在image标签的属性当中（或者CSS中）。我们可以看到在大部分浏览器中的显示效果：
Base64 image

这种做法有利有弊，好处是浏览器可以在一个连接中得到完成的页面内容，不好的地方时图像的大小会增加1/3。因此，这种内嵌的方法适合对小的图形元素比如图标、圆角等等进行处理，从而减少浏览器打开的连接数，但对大的照片、图片（量少而大）等等则不应该使用Base64编码以免影响下载速度。

为了得到刚才的Base64编码，我们将上一篇的Java修改成Struts Action，并借用了JIMI进行图形的读取和格式转换，Base64编码器则改为更普遍的Apache Commons组件，代码如下：

public class Base64ImageAction extends ActionSupport {
private final static String galleryName = "gallery";
private static String parent = null;
private String encodeString = null;
public String getEncodeString() {
return encodeString;
}
public void setEncodeString(String encodeString) {
this.encodeString = encodeString;
}
private String getImageFullPath() {
parent = new File(this.getClass().getClassLoader().getResource(
File.separator).getPath()).getParent()+File.separator+"flag.jpg";
}
public String execute() {
ByteArrayOutputStream output = new ByteArrayOutputStream();
try {
JimiReader reader = Jimi.createJimiReader(this.getImageFullPath());
Image image = reader.getImage();
Jimi.putImage("image/png", image, output);
output.flush();
output.close();
this.encodeString = Base64.encodeBase64String(output.toByteArray());
} catch (IOException e) {
e.printStackTrace();
} catch (JimiException e) {
e.printStackTrace();
}
return SUCCESS;
}
}

对应的View端是个十分简单的Freemarker模板:

<html>
<head>
<title>Hello,World</title>
</head>
<body>
<img src="data:image/png;base64,${encodeString}" />
</body>
</html>

处理古代浏览器
世界总是不是那么完美，尽管大部分现代浏览器对Base64的处理都十分完善，但是我们不能不考虑到一些“古老”的浏览器，而现在还是普遍使用的“古老”的浏览器，就当属IE6，在IE6里试图浏览上面的图片可能会得到一个红叉叉。我们不得不为IE6做一些特殊处理,利用下面的javascript,我们把Base64字串传回服务器端，重新解析成图片

// a regular expression to test for Base64 data
var BASE64_DATA = /^data:.*;base64/i;
// path to the PHP module that will decode the encoded data
var base64Path = "/my/path/base64.php";
function fixBase64(img) {
// check the image source
if (BASE64_DATA.test(img.src)) {
// pass the data to the PHP routine
img.src = base64Path + "?" + img.src.slice(5);
}
};
// fix images on page load
onload = function() {
for (var i = 0; i < document.images.length; i++) {
fixBase64(document.images[i]);
}
};

服务器端的Struts可以参考上面的例子做反向操作，具体从略。

更完美的方法
将Base64传回服务器解码是不错的IE6补丁，但是违背了我们的初衷，对IE6来说，浏览器连接数并未有任何减少。更直接的想法，是否能用Javascript直接在浏览器中，对Base64文本进行解码呢？我们构思的场景如下：服务器端先将图片转换成PNG格式以方便客户端进行处理，Base64编码之后，利用JSON将文本传递给浏览器客户端进行处理。

我们选择PNG图形格式是因为PNG已经俨然成为新的Web图形标准，它格式非常简单，可以很方便的用javascript进行处理而不需要借助浏览器的支持。我们知道javascript直接不能处理二进制数据，但是现在这不是个问题，服务器端已经准备好了Base64编码的文本数据，现在我们只需要一个javascript的Base64解析器，你可以在这里找到一个notmasteryet的Base64解析器。

现在PNG图形格式采用了DEFLATE作为唯一的压缩算法，该算法也广泛应用在ZIP,GZIP等压缩格式中。PNG图像格式文件(或者称为数据流)由一个8字节的PNG文件署名(PNG file signature)域和按照特定结构组织的3个以上的数据块(chunk)组成。

PNG定义了两种类型的数据块，一种是称为关键数据块(critical chunk)，这是标准的数据块，另一种叫做辅助数据块(ancillary chunks)，这是可选的数据块。关键数据块定义了4个标准数据块，其中图像数据块IDAT(image data chunk)：它存储实际的数据, PNG总的数据流采用DEFLAT进行压缩。此外还擦用三角过滤“delta filters”来过滤每一行的像素的未压缩数据。DEFLAT和delta压缩在其他数据和文本处理中也被广泛应用。PNG格式你可以参考<a href="http://www.libpng.org/pub/png/spec/1.1/PNG-Contents.html">官方文档</a>。

很棒的，notmasteryet也为我们提供了一个DEFLAT解压器。

最后，我们把这些组合起来:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Demo JavaScript PNG Viewer</title>
</head>
<body onload="show(gravatar);">
<script src="../Source/Base64.js" type="text/javascript"></script>
<script src="../Source/Deflate.js" type="text/javascript"></script>
<script src="../Source/PNG.js" type="text/javascript"></script>
<script type="text/javascript">
var gravatar = 'iVBORw0KGgoAAAANSUhEUgAAA.......数据从略......55CYII=';
String.prototype.padRight = function(c, n){
var txt = '';
for(var i=0;i<n-this.length;i++) txt += c;
return txt + this;
};
function show(data){
var png = new PNG(data);
var img = document.getElementById('image'), limg = document.getElementById('largeimage');
document.getElementById('nativeimage').src = 'data:image/png;base64,' + data;
img.innerHTML = '';
limg.innerHTML = '';
img.style.width = png.width + 'px';
img.style.height = png.height + 'px';
limg.style.width = (png.width * 3) + 'px';
limg.style.width = (png.height * 3) + 'px';
var line;
while(line = png.readLine())
{
for (var x = 0; x < line.length; x++){
var px = document.createElement('div'), px2 = document.createElement('div');
px.className = px2.className = 'pixel';
px.style.backgroundColor = px2.style.backgroundColor = '#' + line[x].toString(16).padRight('0', 6);
img.appendChild(px);
limg.appendChild(px2);
}
}
}
</script>
<div id="image"></div>
<div id="largeimage"></div>
<img id="nativeimage" />
</body>
</html>

相关的javascript请到blogs.ejb.cc下载。

还可以更完美
回顾上一篇的例子，我们用了ihard.net提供了Base64编码，它提供一个GZIP编码参数，你可以发现如此编码之后的文本大小和原来的图形大小相差无几。利用上一节提供了javascript是不是可以解决Base64编码后文件大小增加的问题？留着思考吧。

http://blog.csdn.net/elf8848/article/details/39927385

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