Java 中图片与二进制之间如何相互转换？

Dear 丶 2023-09-24 15:34 58阅读 0赞

#### 1、 下面是一个完整的代码示例。 ####

*  指定文件路径转为二进制
 *  将网络图片转为二进制
 *  base64 转为图片资源

package com.xxx.example.file;
    
    import java.awt.image.BufferedImage;
    import java.io.ByteArrayInputStream;
    import java.io.ByteArrayOutputStream;
    import java.io.File;
    import java.io.IOException;
    import java.io.InputStream;
    import java.net.HttpURLConnection;
    import java.net.URL;
    
    import javax.imageio.ImageIO;
    
    import com.zxtc.syonline.support.common.StringUtil;
    
    import sun.misc.BASE64Decoder;
    import sun.misc.BASE64Encoder;
    
    public class ImageBioChangeUtil {
    	
    	static BASE64Encoder encoder = new sun.misc.BASE64Encoder();   
        static BASE64Decoder decoder = new sun.misc.BASE64Decoder();
        
        //从文件路径中获取图片转为二进制
    	public static String getImageBinary(String filePath){
    		if(StringUtil.isEmpty(filePath)) {
    			return null;
    		}
            File f = new File(filePath);	//这里gif动态图不可以，虽然在后面也能输出gif格式，但是却不是动图
            BufferedImage bi;   
            try {   
                bi = ImageIO.read(f);   
                ByteArrayOutputStream baos = new ByteArrayOutputStream();   
                ImageIO.write(bi, "jpg", baos);   
                byte[] bytes = baos.toByteArray();   
                   
                return encoder.encodeBuffer(bytes).trim();   
            } catch (IOException e) {   
                e.printStackTrace();   
            }   
            return null;   
        }
    	//从URl中获取图片转为二进制
    	public static String getImageBinaryFromUrl(String urlPath) throws Exception{
    		if(StringUtil.isEmpty(urlPath)) {
    			return "";
    		}
    		URL url=new URL(urlPath);
            HttpURLConnection conn= (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(3000);//超时提示1秒=1000毫秒
            InputStream inStream=conn.getInputStream();//获取输出流
            byte[] data=readInputStream(inStream);
    		return encoder.encodeBuffer(data).trim();   
    		
    	}   
    	 //readInputStream方法
        private static byte[] readInputStream(InputStream inStream) throws Exception{
            ByteArrayOutputStream outStream=new ByteArrayOutputStream();
            byte[] buffer=new byte[1024];//转换为二进制
            int len=0;
            while((len =inStream.read(buffer))!=-1){
                outStream.write(buffer,0,len);
            }
            return  outStream.toByteArray();
        }
        //将二进制转为图片
        public static void base64StringToImage(String base64String,String outFilePath){
        	if(StringUtil.isNotEmpty(base64String)&&StringUtil.isNotEmpty(outFilePath)) {
        		try {   
                    byte[] bytes1 = decoder.decodeBuffer(base64String);   
                       
                    ByteArrayInputStream bais = new ByteArrayInputStream(bytes1);   
                    BufferedImage bi1 =ImageIO.read(bais);   
                    File w2 = new File(outFilePath);//可以是jpg,png格式   
                    if (!w2.exists()) {   //文件不存在则创建文件，先创建目录
                        File dir = new File(w2.getParent());
                        dir.mkdirs();
                        w2.createNewFile(); // 创建新文件
                    }
                    ImageIO.write(bi1, "jpg", w2);//不管输出什么格式图片，此处不需改动   
                } catch (IOException e) {   
                    e.printStackTrace();   
                }   
    		}
        }
        
        public static void main(String[] args) {
        	String imageBinary=null;
    		try {
    			imageBinary = getImageBinaryFromUrl("");
    		} catch (Exception e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
            System.out.println(imageBinary);   
            String outFilePath= "E://test//bio//zhh/aa.png";   
            base64StringToImage(imageBinary,outFilePath);   
        }
    }

#### 2、如何判断 base64 图片的格式？ ####

//判断图片base64字符串的文件格式
    	public static String checkImageBase64Format(String base64ImgData) {
    		byte[] b = Base64Util.decode(base64ImgData);
    		String type = "";
    		if (0x424D == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
    			type = "bmp";
    		} else if (0x8950 == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
    			type = "png";
    		} else if (0xFFD8 == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
    			type = "jpg";
    		}
    		return type;
    	}

#### 3、将网络图片转为 base64 字符串 ####

/**
         * 将网络路径图片转为base64的格式
         * @param requestUrl 请求网络路径
         * @throws Exception
         */
        public static String getUrlImageToBase64(String requestUrl) throws Exception {
            ByteArrayOutputStream data = new ByteArrayOutputStream();
            try {
                // 创建URL
                URL url = new URL(requestUrl);
                byte[] by = new byte[1024];
    
                // 创建链接
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.setRequestMethod("GET");
                conn.setConnectTimeout(5 * 1000);
                InputStream is = conn.getInputStream();
    
                // 将内容读取内存中
                int len = -1;
                while ((len = is.read(by)) != -1) {
                    data.write(by, 0, len);
                }
    
                // 关闭流
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
    
            // 对字节数组Base64编码
            Base64.Encoder encoder = Base64.getEncoder();
    //        return "data:image/" + photoType + ";base64," + encoder.encodeToString(data.toByteArray());
            return encoder.encodeToString(data.toByteArray());
        }

#### 4、将 base64 字符串转为图片输出 ####

/**
    	 * 将Base64编码的字符串转为文件输出
    	 * @param base64String 字符串
         * @param path 输出文件保存路径
    	 * @param fileName 输出文件名称
    	 * @return 是否转换成功
    	 */
    	public static boolean writeFileFromBase64(String base64String, String path, String fileName) {
    		if (base64String == null){
    			return false;
    		}
    		try	{
    			byte[] b = Base64Util.decode(base64String);
    			File file = new File(path);
    			if(!file.exists()){
    				makeDir(file);
    			}
    			OutputStream out = new FileOutputStream(path + fileName);
    			out.write(b);
    			out.flush();
    			out.close();
    			return true;
    		}catch(Exception e){
    			e.printStackTrace();
    			return false;
    		}
    	}

*注：该方法的入参，base64 格式文件不得有 文件头部标识信息，否则会转换失败。所以这里我们需要自行判断是否包含有头部信息。*

String urlImageToBase64 = "";//这里就是我们图片的base64字符串
    if(urlImageToBase64.indexOf(",")>-1) {//包含头信息
    				System.out.println("包含头部信息");
    				urlImageToBase64 = urlImageToBase64.substring(urlImageToBase64.indexOf(",")+1);
    }

#### 5、将文件转为 base64 字符串 ####

/**
    	 * 读入文件转换为Base64编码并返回
    	 * @param filePath 文件路径
    	 * @return base64 的文件
    	 * @throws Exception
    	 */
    	public static String readAsBase64FromFile(String filePath) {	
    		InputStream in = null;
    		byte[] data = null;
    		
    		try	{
    			in = new FileInputStream(fileName);
    			data = new byte[in.available()];
    			in.read(data);
    			in.close();
    		} catch(Exception e) {
    			e.printStackTrace();
    			return null;
    		}
    		return Base64Util.encode(data);
    	}

上面用到了一个 ***Base64Util.java***

package com.xxx.example.util;
    
    public final class Base64Util {
    
    	static private final int BASELENGTH = 128;
    	static private final int LOOKUPLENGTH = 64;
    	static private final int TWENTYFOURBITGROUP = 24;
    	static private final int EIGHTBIT = 8;
    	static private final int SIXTEENBIT = 16;
    	static private final int FOURBYTE = 4;
    	static private final int SIGN = -128;
    	static private final char PAD = '=';
    	static private final boolean fDebug = false;
    	static final private byte[] base64Alphabet = new byte[BASELENGTH];
    	static final private char[] lookUpBase64Alphabet = new char[LOOKUPLENGTH];
    
    	static {
    		for (int i = 0; i < BASELENGTH; ++i) {
    			base64Alphabet[i] = -1;
    		}
    		for (int i = 'Z'; i >= 'A'; i--) {
    			base64Alphabet[i] = (byte) (i - 'A');
    		}
    		for (int i = 'z'; i >= 'a'; i--) {
    			base64Alphabet[i] = (byte) (i - 'a' + 26);
    		}
    
    		for (int i = '9'; i >= '0'; i--) {
    			base64Alphabet[i] = (byte) (i - '0' + 52);
    		}
    
    		base64Alphabet['+'] = 62;
    		base64Alphabet['/'] = 63;
    
    		for (int i = 0; i <= 25; i++) {
    			lookUpBase64Alphabet[i] = (char) ('A' + i);
    		}
    
    		for (int i = 26, j = 0; i <= 51; i++, j++) {
    			lookUpBase64Alphabet[i] = (char) ('a' + j);
    		}
    
    		for (int i = 52, j = 0; i <= 61; i++, j++) {
    			lookUpBase64Alphabet[i] = (char) ('0' + j);
    		}
    		lookUpBase64Alphabet[62] = (char) '+';
    		lookUpBase64Alphabet[63] = (char) '/';
    
    	}
    
    	private static boolean isWhiteSpace(char octect) {
    		return (octect == 0x20 || octect == 0xd || octect == 0xa || octect == 0x9);
    	}
    
    	private static boolean isPad(char octect) {
    		return (octect == PAD);
    	}
    
    	private static boolean isData(char octect) {
    		return (octect < BASELENGTH && base64Alphabet[octect] != -1);
    	}
    
    	/**
    	 * Encodes hex octects into Base64
    	 *
    	 * @param binaryData
    	 *            Array containing binaryData
    	 * @return Encoded Base64 array
    	 */
    	public static String encode(byte[] binaryData) {
    
    		if (binaryData == null) {
    			return null;
    		}
    
    		int lengthDataBits = binaryData.length * EIGHTBIT;
    		if (lengthDataBits == 0) {
    			return "";
    		}
    
    		int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
    		int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
    		int numberQuartet = fewerThan24bits != 0 ? numberTriplets + 1 : numberTriplets;
    		char encodedData[] = null;
    
    		encodedData = new char[numberQuartet * 4];
    
    		byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;
    
    		int encodedIndex = 0;
    		int dataIndex = 0;
    		if (fDebug) {
    			System.out.println("number of triplets = " + numberTriplets);
    		}
    
    		for (int i = 0; i < numberTriplets; i++) {
    			b1 = binaryData[dataIndex++];
    			b2 = binaryData[dataIndex++];
    			b3 = binaryData[dataIndex++];
    
    			if (fDebug) {
    				System.out.println("b1= " + b1 + ", b2= " + b2 + ", b3= " + b3);
    			}
    
    			l = (byte) (b2 & 0x0f);
    			k = (byte) (b1 & 0x03);
    
    			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
    			byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
    			byte val3 = ((b3 & SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6 ^ 0xfc);
    
    			if (fDebug) {
    				System.out.println("val2 = " + val2);
    				System.out.println("k4   = " + (k << 4));
    				System.out.println("vak  = " + (val2 | (k << 4)));
    			}
    
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
    		}
    
    		// form integral number of 6-bit groups
    		if (fewerThan24bits == EIGHTBIT) {
    			b1 = binaryData[dataIndex];
    			k = (byte) (b1 & 0x03);
    			if (fDebug) {
    				System.out.println("b1=" + b1);
    				System.out.println("b1<<2 = " + (b1 >> 2));
    			}
    			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
    			encodedData[encodedIndex++] = PAD;
    			encodedData[encodedIndex++] = PAD;
    		} else if (fewerThan24bits == SIXTEENBIT) {
    			b1 = binaryData[dataIndex];
    			b2 = binaryData[dataIndex + 1];
    			l = (byte) (b2 & 0x0f);
    			k = (byte) (b1 & 0x03);
    
    			byte val1 = ((b1 & SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2 ^ 0xc0);
    			byte val2 = ((b2 & SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4 ^ 0xf0);
    
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
    			encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
    			encodedData[encodedIndex++] = PAD;
    		}
    
    		return new String(encodedData);
    	}
    
    	/**
    	 * Decodes Base64 data into octects
    	 *
    	 * @param encoded
    	 *            string containing Base64 data
    	 * @return Array containind decoded data.
    	 */
    	public static byte[] decode(String encoded) {
    
    		if (encoded == null) {
    			return null;
    		}
    
    		char[] base64Data = encoded.toCharArray();
    		// remove white spaces
    		int len = removeWhiteSpace(base64Data);
    
    		if (len % FOURBYTE != 0) {
    			return null;// should be divisible by four
    		}
    
    		int numberQuadruple = (len / FOURBYTE);
    
    		if (numberQuadruple == 0) {
    			return new byte[0];
    		}
    
    		byte decodedData[] = null;
    		byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
    		char d1 = 0, d2 = 0, d3 = 0, d4 = 0;
    
    		int i = 0;
    		int encodedIndex = 0;
    		int dataIndex = 0;
    		decodedData = new byte[(numberQuadruple) * 3];
    
    		for (; i < numberQuadruple - 1; i++) {
    
    			if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))
    					|| !isData((d3 = base64Data[dataIndex++])) || !isData((d4 = base64Data[dataIndex++]))) {
    				return null;
    			} // if found "no data" just return null
    
    			b1 = base64Alphabet[d1];
    			b2 = base64Alphabet[d2];
    			b3 = base64Alphabet[d3];
    			b4 = base64Alphabet[d4];
    
    			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
    			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
    			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
    		}
    
    		if (!isData((d1 = base64Data[dataIndex++])) || !isData((d2 = base64Data[dataIndex++]))) {
    			return null;// if found "no data" just return null
    		}
    
    		b1 = base64Alphabet[d1];
    		b2 = base64Alphabet[d2];
    
    		d3 = base64Data[dataIndex++];
    		d4 = base64Data[dataIndex++];
    		if (!isData((d3)) || !isData((d4))) {// Check if they are PAD characters
    			if (isPad(d3) && isPad(d4)) {
    				if ((b2 & 0xf) != 0)// last 4 bits should be zero
    				{
    					return null;
    				}
    				byte[] tmp = new byte[i * 3 + 1];
    				System.arraycopy(decodedData, 0, tmp, 0, i * 3);
    				tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
    				return tmp;
    			} else if (!isPad(d3) && isPad(d4)) {
    				b3 = base64Alphabet[d3];
    				if ((b3 & 0x3) != 0)// last 2 bits should be zero
    				{
    					return null;
    				}
    				byte[] tmp = new byte[i * 3 + 2];
    				System.arraycopy(decodedData, 0, tmp, 0, i * 3);
    				tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
    				tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
    				return tmp;
    			} else {
    				return null;
    			}
    		} else { // No PAD e.g 3cQl
    			b3 = base64Alphabet[d3];
    			b4 = base64Alphabet[d4];
    			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
    			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
    			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
    
    		}
    
    		return decodedData;
    	}
    
    	/**
    	 * remove WhiteSpace from MIME containing encoded Base64 data.
    	 *
    	 * @param data
    	 *            the byte array of base64 data (with WS)
    	 * @return the new length
    	 */
    	private static int removeWhiteSpace(char[] data) {
    		if (data == null) {
    			return 0;
    		}
    
    		// count characters that's not whitespace
    		int newSize = 0;
    		int len = data.length;
    		for (int i = 0; i < len; i++) {
    			if (!isWhiteSpace(data[i])) {
    				data[newSize++] = data[i];
    			}
    		}
    		return newSize;
    	}
    }

--------------------

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