Java通过图片url地址获取图片base64位字符串的两种方式
工作中遇到通过图片的url获取图片base64位的需求。一开始是用网上的方法，通过工具类Toolkit，虽然实现的代码比较简短，不过偶尔会遇到图片转成base64位不正确的情况，至今不知道为啥。
之后，又去网上搜了通过获取图片的二进制流转换成base64的方式，两种方式，都是亲测有效，通过Toolkit偶尔会出现，转base64后，展示不完整的问题。所以建议用通过下载二进制流转换的方式进行转换。
下面附上代码：
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import java.awt.Graphics;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.Transparency;
import java.net.HttpURLConnection;
import java.net.URL;
public class ImageUtils {
public static String getBase64ByImgUrl(String url){
String suffix = url.substring(url.lastIndexOf(".") + 1);
try {
URL urls = new URL(url);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
Image image = Toolkit.getDefaultToolkit().getImage(urls);
BufferedImage biOut = toBufferedImage(image);
ImageIO.write(biOut, suffix, baos);
String base64Str = Base64Util.encode(baos.toByteArray());
return base64Str;
} catch (Exception e) {
return "";
}
}
public static BufferedImage toBufferedImage(Image image) {
if (image instanceof BufferedImage) {
return (BufferedImage) image;
}
// This code ensures that all the pixels in the image are loaded
image = new ImageIcon(image).getImage();
BufferedImage bimage = null;
GraphicsEnvironment ge = GraphicsEnvironment
.getLocalGraphicsEnvironment();
try {
int transparency = Transparency.OPAQUE;
GraphicsDevice gs = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gs.getDefaultConfiguration();
bimage = gc.createCompatibleImage(image.getWidth(null),
image.getHeight(null), transparency);
} catch (HeadlessException e) {
// The system does not have a screen
}
if (bimage == null) {
// Create a buffered image using the default color model
int type = BufferedImage.TYPE_INT_RGB;
bimage = new BufferedImage(image.getWidth(null),
image.getHeight(null), type);
}
// Copy image to buffered image
Graphics g = bimage.createGraphics();
// Paint the image onto the buffered image
g.drawImage(image, 0, 0, null);
g.dispose();
return bimage;
}
/**
* 通过图片的url获取图片的base64字符串
* @param imgUrl 图片url
* @return 返回图片base64的字符串
*/
public static String image2Base64(String imgUrl) {
URL url = null;
InputStream is = null;
ByteArrayOutputStream outStream = null;
HttpURLConnection httpUrl = null;
try{
url = new URL(imgUrl);
httpUrl = (HttpURLConnection) url.openConnection();
httpUrl.connect();
httpUrl.getInputStream();
is = httpUrl.getInputStream();
outStream = new ByteArrayOutputStream();
//创建一个Buffer字符串
byte[] buffer = new byte[1024];
//每次读取的字符串长度，如果为-1，代表全部读取完毕
int len = 0;
//使用一个输入流从buffer里把数据读取出来
while( (len=is.read(buffer)) != -1 ){
//用输出流往buffer里写入数据，中间参数代表从哪个位置开始读，len代表读取的长度
outStream.write(buffer, 0, len);
}
// 对字节数组Base64编码
return Base64Util.encode(outStream.toByteArray());
}catch (Exception e) {
e.printStackTrace();
}
finally{
if(is != null)
{
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(outStream != null)
{
try {
outStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(httpUrl != null)
{
httpUrl.disconnect();
}
}
return imgUrl;
}
}
其中
getBase64ByImgUrl方法为通过Toolkit获取的方式，至于为啥没注释，因为我也看不懂原理，也是抄来的。
image2Base64方法为通过下载二进制流的方式，当然也是抄来的。写出来是为了总结一下。下次遇到相同的问题，不用到处查了。
附上Base64Util的代码：
1 import java.io.ByteArrayOutputStream;
2 import java.io.File;
3 import java.io.IOException;
4 import java.util.regex.Matcher;
5 import java.util.regex.Pattern;
6
7 import javax.imageio.stream.FileImageInputStream;
8
9 import sun.misc.BASE64Decoder;
10 import sun.misc.BASE64Encoder;
11
12 public class Base64Util{
13 /**
14 * 字符串转图片
15 * @param base64Str
16 * @return
17 */
18 public static byte[] decode(String base64Str){
19 byte[] b = null;
20 BASE64Decoder decoder = new BASE64Decoder();
21 try {
22 b = decoder.decodeBuffer(replaceEnter(base64Str));
23 } catch (IOException e) {
24 e.printStackTrace();
25 }
26 return b;
27 }
28
29 /**
30 * 图片转字符串
31 * @param image
32 * @return
33 */
34 public static String encode(byte[] image){
35 BASE64Encoder decoder = new BASE64Encoder();
36 return replaceEnter(decoder.encode(image));
37 }
38
39 public static String encode(String uri){
40 BASE64Encoder encoder = new BASE64Encoder();
41 return replaceEnter(encoder.encode(uri.getBytes()));
42 }
43
44 /**
45 *
46 * @path 图片路径
47 * @return
48 */
49
50 public static byte[] imageTobyte(String path){
51 byte[] data = null;
52 FileImageInputStream input = null;
53 try {
54 input = new FileImageInputStream(new File(path));
55 ByteArrayOutputStream output = new ByteArrayOutputStream();
56 byte[] buf = new byte[1024];
57 int numBytesRead = 0;
58 while((numBytesRead = input.read(buf)) != -1){
59 output.write(buf, 0, numBytesRead);
60 }
61 data = output.toByteArray();
62 output.close();
63 input.close();
64
65 } catch (Exception e) {
66 e.printStackTrace();
67 }
68
69 return data;
70 }
71
72
73
74 public static String replaceEnter(String str){
75 String reg ="[\n-\r]";
76 Pattern p = Pattern.compile(reg);
77 Matcher m = p.matcher(str);
78 return m.replaceAll("");
79 }
80
81
82 }
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