Java - 将图像转换为Base64

Question

我在将gif图像转换为基本64字符串时遇到问题。

当我转换它时，代码为我增加了10万个AAAAAA，而图像真的很小！

这里是我的代码：

import java.io.BufferedWriter; 
import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileWriter; 
import java.util.ArrayList; 

public class Main 
{ 

    public static void main(String[] args) 
    { 
     try 
     { 
      FileWriter fstream = new FileWriter("./out.txt"); 
      BufferedWriter out = new BufferedWriter(fstream); 

      File folder = new File("./flags/"); 
      File[] listOfFiles = folder.listFiles(); 

      for (int i = 0; i < listOfFiles.length; i++) 
      { 
       if (listOfFiles[i].isFile()) 
       { 
        Main.readFile(out, listOfFiles[i]); 
       } 
      } 

      out.close(); 
      System.out.println("Done"); 
     } 
     catch (Exception e) {} 
    } 

    public static void readFile(BufferedWriter out, File file) 
    { 
     try 
     { 
      byte[] byteArray = new byte[102400]; 
      FileInputStream fis = new FileInputStream(file); 
      String base64String; 
      int bytesRead = 0; 
      while ((bytesRead = fis.read(byteArray)) != -1) 
      { 
       new String(byteArray, 0, bytesRead); 
       base64String = Base64.encode(byteArray); 
       out.write("public static ImageIcon getFlag" + file.getName() + "()"); 
       out.newLine(); 
       out.write("{"); 
       out.newLine(); 
       ArrayList<String> array = Main.cut(base64String); 
       out.write("return Utils.toImage(\"" + array.get(0) + "\""); 
       for (int i=1; i<array.size()-1; i++) 
       { 
        out.write("<tab>+\"" + array.get(i) + "\""); 
       } 
       out.write("<tab>\"" + array.get(array.size() - 1) + "\");"); 
       out.newLine(); 
       out.write("}"); 
       out.newLine(); 
       out.newLine(); 
      } 
     } 
     catch (Exception e) 
     { 
      e.printStackTrace(); 
     } 
    } 

    public static ArrayList<String> cut(String in) 
    { 
     ArrayList<String> array = new ArrayList<String>(); 
     while (in.length() > 76) 
     { 
      array.add(in.substring(0, 77)); 
      in = in.substring(77); 
     } 
     return array; 
    } 
} 

Basicaly，它在一个文本文件out.txt一堆Java方法里面基64码写入。

这里是输出的（小）部分：

return Utils.toImage("R0lGODlhEAALANUAANPTAPZva/n5AfLySPz8iYqY3O01NgoksbGZa+kYGOskJKi05vb2XZ+r4+05O"<tab>+"Pv7eO3tKPv7bZak4dSvebC76tC2iPNISPX1UMkAAMm6U/NWTeYAAF5y1LqlevNaWpSh3e7uQ+1CQt"<tab>+"gAAKOv5Vds1C1IvpGf37a/7OnTYZ6q6NGkamd71/LyPusvLvFiTEFbx9rPb/HuaczATd7eAPAAAH2"<tab>+"N2vE+PMqiYuXQUsKufJqn4jlRxUlhy+CpelFnz/PxbyH5BAAAAAAALAAAAAAQAAsAAAaQwBVnSBIY"<tab>+"jzTaZsk5OSmEKOHxCAQ8nk1zMUo9Ir8Y42Kx2Dyi5qihi1QqkxzZZtCISBS2JNILoFQDdC0WIj4UO"<tab>+"hImDBMoLjcsBi0KISI8C4kFMB0uOAgykgkOGC8LJgUFFx0IqxAKCQkGGDsjpzUDLBkZEBCvCS0YJW"<tab>+"wfBQxjAyAgDpG/OwfOBzPRANMY1dVBADsAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab>+"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"<tab> 

感谢。

编辑：我使用的base64编码从这样一个问题：https://stackoverflow.com/a/4265472/1295422

Answer 1

byte[] byteArray = new byte[102400]; 
base64String = Base64.encode(byteArray); 

无论数据中实际使用多少数据，该代码都会对102400个字节进行编码。

while ((bytesRead = fis.read(byteArray)) != -1) 

你需要使用bytesRead的地方值。另外，这可能不会一次将整个文件读入数组中（它只读取I/O缓冲区中的数据），因此您的循环可能不起作用，最终可能会有一半图像在你的数组中。

我在这里使用Apache的百科全书IOUtils：

Base64.encode(FileUtils.readFileToByteArray(file)); 

Answer 2

首先，这行代码：

while ((bytesRead = fis.read(byteArray)) != -1) 

相当于

while ((bytesRead = fis.read(byteArray, 0, byteArray.length)) != -1) 

所以这写入从offset 0开始的byteArray，而不是从之前写入的地方开始。

你需要的东西是这样的：

int offset = 0; 
int bytesRead = 0; 

while ((bytesRead = fis.read(byteArray, offset, byteArray.length - offset) != -1) { 
    offset += bytesRead; 
} 

您在随后读取数据（字节）后，就可以将其转换为Base64。

虽然存在更大的问题 - 您使用的是固定大小的数组，因此太大的文件将无法正确转换，并且代码也因此而更加狡猾。

我会沟字节数组，像这样的东西去：

ByteArrayOutputStream buffer = new ByteArrayOutputStream(); 
// commons-io IOUtils 
IOUtils.copy(fis, buffer); 
byte [] data = buffer.toByteArray(); 
Base64.encode(data); 

或进一步压缩它作为蒂洛与文件实用程序。

Answer 3

线

base64String = Base64.encode(byteArray); 

全阵列（102400个字节）为Base64，不只是你读取的字节数转换。你需要传递它的字节数。

Answer 4

new String(byteArray, 0, bytesRead);不修改数组。您需要使用System.arrayCopy将阵列修剪为实际的数据大小。否则，你正在处理所有102400字节，其中大部分是零。

Answer 5

晚GraveDig ...只要你限制字节数组文件的大小。

FileInputStream fis = new FileInputStream(file); 
byte[] byteArray= new byte[(int) file.length()]; 

Answer 6

您可以使用File对象获取文件的长度来初始化数组：

int length = Long.valueOf(file.length()).intValue(); 
byte[] byteArray = new byte[length]; 

Answer 7

您可以创建一个大阵，然后将其复制到使用System.arrayCopy一个新的数组

 int contentLength = 100000000; 
     byte[] byteArray = new byte[contentLength]; 

     BufferedInputStream inputStream = new BufferedInputStream(connection.getInputStream()); 
     while ((bytesRead = inputStream.read()) != -1) 
     { 
      byteArray[count++] = (byte)bytesRead; 
     } 

     byte[] destArray = new byte[count]; 
     System.arraycopy(byteArray, 0, destArray , 0, count); 

destArray将包含你想

Answer 8

的信息我知道这是一个老问题，但也许有人会发现我的代码示例有用。此代码在Base64中编码文件，然后对其进行解码并将其保存在新位置。

import java.io.IOException; 
import java.nio.file.Files; 
import java.nio.file.Path; 
import java.nio.file.Paths; 
import java.util.Arrays; 

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

public class Base64Example { 

    public static void main(String[] args) { 

     Base64Example tempObject = new Base64Example(); 

     // convert file to regular byte array 
     byte[] codedFile = tempObject.convertFileToByteArray("your_input_file_path"); 

     // encoded file in Base64 
     byte[] encodedFile = Base64.encodeBase64(codedFile); 

     // print out the byte array 
     System.out.println(Arrays.toString(encodedFile)); 

     // print the encoded String 
     System.out.println(encodedFile); 

     // decode file back to regular byte array 
     byte[] decodedByteArray = Base64.decodeBase64(encodedFile); 

     // save decoded byte array to a file 
     boolean success = tempObject.saveFileFromByteArray("your_output_file_path", decodedByteArray); 

     // print out success 
     System.out.println("success : " + success); 
    } 

    public byte[] convertFileToByteArray(String filePath) { 

     Path path = Paths.get(filePath); 

     byte[] codedFile = null; 

     try { 
      codedFile = Files.readAllBytes(path); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

     return codedFile; 
    } 

    public boolean saveFileFromByteArray(String filePath, byte[] decodedByteArray) { 

     boolean success = false; 

     Path path = Paths.get(filePath); 

     try { 
      Files.write(path, decodedByteArray); 
      success = true; 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

     return success; 
    } 
}