Java判断图片文件格式，不是根据文件后缀判断

系统管理员 2023-06-20 04:59 51阅读 0赞

1、创建测试类（FileUtils.java）

package com.jeff.utils;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    
    public class FileUtils { 
    
    	public static final String TYPE_JPG = "jpg";
    	public static final String TYPE_GIF = "gif";
    	public static final String TYPE_PNG = "png";
    	public static final String TYPE_BMP = "bmp";
    	public static final String TYPE_UNKNOWN = "unknown";
    
    	/** * * @description: 根据文件流判断图片类型 * @author: Jeff * @date: 2019年12月7日 * @param fis 文件输入流 * @return */
    	public static String getPicType(FileInputStream fis) { 
    		// 读取文件的前几个字节来判断图片格式
    		byte[] b = new byte[4];
    		try { 
    			fis.read(b, 0, b.length);
    			String type = bytesToHexString(b).toUpperCase();
    			if (type.contains("FFD8FF")) { 
    				return TYPE_JPG;
    			} else if (type.contains("89504E47")) { 
    				return TYPE_PNG;
    			} else if (type.contains("47494638")) { 
    				return TYPE_GIF;
    			} else if (type.contains("424D")) { 
    				return TYPE_BMP;
    			} else { 
    				return TYPE_UNKNOWN;
    			}
    		} catch (IOException e) { 
    			e.printStackTrace();
    		} finally { 
    			if (fis != null) { 
    				try { 
    					fis.close();
    				} catch (IOException e) { 
    					e.printStackTrace();
    				}
    			}
    		}
    		return null;
    	}
    
    	/** * * @description: byte数组转换成16进制字符串 * @author: Jeff * @date: 2019年12月7日 * @param src * @return */
    	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();
    	}
    
    	public static void main(String[] args) { 
    		try { 
    			System.out.println("图片1格式： " + getPicType(new FileInputStream(new File("F:\\Jeff\\images\\jie.jpg"))));
    			System.out.println("图片2格式： " + getPicType(new FileInputStream(new File("F:\\Jeff\\images\\1.png"))));
    			System.out.println("图片3格式： " + getPicType(new FileInputStream(new File("F:\\Jeff\\images\\2.gif"))));
    			System.out.println("图片4格式： " + getPicType(new FileInputStream(new File("F:\\Jeff\\images\\3.bmp"))));
    			System.out.println("图片5格式： " + getPicType(new FileInputStream(new File("F:\\Jeff\\images\\jie.png"))));
    		} catch (FileNotFoundException e) { 
    			e.printStackTrace();
    		}
    	}
    
    }

2、控制台输出结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTczOTcyMA_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTczOTcyMA_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191207192425466.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTczOTcyMA==,size_16,color_FFFFFF,t_70