前言

常见的图像任务通常需要把照片统一成相同的格式，所以此文章正是为了统一格式而生，常见的主要有cv2和PIL.Image的相关操作，照片格式是一串数字加上后缀名

工具一：cv2

pip install opencv-python

之后就可以

import cv2

1.1 导包

import os

import cv2

import sys

import numpy as np

1.2 路径设置

path = r"C:\\Users\\86775\\test_change\\"
path2 = r"C:\\Users\\86775\\test_change2\\"

1.3 改格式重新传

1.3.1 用os.path.splitext()来判断

images = os.listdir(path)
for i in os.listdir(path):
    print(os.path.splitext(i))  # ('34474006827920603', '.png')
    if os.path.splitext(i)[1] == ".jpeg":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".jpeg", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif os.path.splitext(i)[1] == ".png":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".png", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif os.path.splitext(i)[1] == ".JPG":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".JPG", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif os.path.splitext(i)[1] == ".PNG":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".PNG", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif os.path.splitext(i)[1] == ".jpg":
        img = cv2.imread(path + i)
        # print(img)
        cv2.imwrite(path2 + i, img)

1.3.2 用split()来判断

images = os.listdir(path)
for i in os.listdir(path):
    print(i.split("."))
    if i.split(".")[1] == "jpeg":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".jpeg", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif i.split(".")[1] == "png":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".png", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif i.split(".")[1] == "JPG":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".JPG", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif i.split(".")[1] == "PNG":
        img = cv2.imread(path + i)
        # print(img)
        new_imagename = i.replace(".PNG", ".jpg")
        cv2.imwrite(path2 + new_imagename, img)
 
    elif i.split(".")[1] == "jpg":
        img = cv2.imread(path + i)
        # print(img)
        cv2.imwrite(path2 + i, img)

1.4 查看结果

工具二：pillow

pip install pillow

之后就可以

from PIL import Image

2.1 导包

import os

from PIL import Image

2.2 路径设置

path = r"C:\\Users\\86775\\test_change\\"
path2 = r"C:\\Users\\86775\\test_change2\\"

2.3 写格式修改函数

RGBA意思是红色，绿色，蓝色，Alpha的色彩空间，Alpha指透明度，而JPG不支持透明度。
所以其他格式不转jpg可以直接保存为.png格式，转jpg就需要丢弃Alpha
img = img.convert(“RGB”)，转换成RGB，保证和jpg格式的通道数相同，也算一种图片类型变换的防报错机制

def jpeg2jpg(path_in, path_out):
    img = Image.open(path_in)
    img = img.convert("RGB")
    img.save(path_out, "JPEG", quality=80, optimize=True, progressive=True)
 
 
def png2jpg(path_in, path_out):
    img = Image.open(path_in)
    img = img.convert("RGB")
    img.save(path_out, "JPEG", quality=80, optimize=True, progressive=True)
 
 
def JPG2jpg(path_in, path_out):
    img = Image.open(path_in)
    img = img.convert("RGB")
    img.save(path_out, "JPEG", quality=80, optimize=True, progressive=True)
 
 
def PNG2jpg(path_in, path_out):
    img = Image.open(path_in)
    img = img.convert("RGB")
    img.save(path_out, "JPEG", quality=80, optimize=True, progressive=True)
 
 
def jpg2jpg(path_in, path_out):
    img = Image.open(path_in)
    img = img.convert("RGB")
    img.save(path_out, "JPEG", quality=80, optimize=True, progressive=True)

2.4 开始转换

images = os.listdir(path1)
for i in images:
    print(i)
    if os.path.splitext(i)[1] == ".jpeg":
        source = path1 + "\\" + str(i.split(".")[0]) + ".jpeg"
        target = path2 + "\\" + str(i.split(".")[0]) + ".jpg"
        jpeg2jpg(source, target)
    elif os.path.splitext(i)[1] == ".png":
        source = path1 + "\\" + str(i.split(".")[0]) + ".png"
        target = path2 + "\\" + str(i.split(".")[0]) + ".jpg"
        png2jpg(source, target)
    elif os.path.splitext(i)[1] == ".JPG":
        source = path1 + "\\" + str(i.split(".")[0]) + ".JPG"
        target = path2 + "\\" + str(i.split(".")[0]) + ".jpg"
        JPG2jpg(source, target)
    elif os.path.splitext(i)[1] == ".PNG":
        source = path1 + "\\" + str(i.split(".")[0]) + ".PNG"
        target = path2 + "\\" + str(i.split(".")[0]) + ".jpg"
        PNG2jpg(source, target)
    elif os.path.splitext(i)[1] == ".jpg":
        source = path1 + "\\" + str(i.split(".")[0]) + ".jpg"
        target = path2 + "\\" + str(i.split(".")[0]) + ".jpg"
        jpg2jpg(source, target)

2.5 查看结果

判断文件是否为图片格式

原理：1、使用JDK类库解析文件数据，如果能解析成功，获得图片长宽，即为正确的图片格式

           2、解析文件头信息，判断图片类型

工具代码

    /**
	 * 判断文件后缀是否为图片文件格式,bmp|gif|jpg|jpeg|png 返回true
	 * @param imageFileSuffix 图片文件后缀名
	 * @return
	 */
	public static boolean isImageBySuffix(String imageFileSuffix) {
		if (StringUtils.isNotEmpty(imageFileSuffix)) {
			//[JPG, jpg, bmp, BMP, gif, GIF, WBMP, png, PNG, wbmp, jpeg, JPEG]
			String[] formatNames = ImageIO.getReaderFormatNames();
			if (ArrayUtils.isNotEmpty(formatNames)) {
				for (String formatName : formatNames) {
					if (imageFileSuffix.toLowerCase().equals(formatName)) {
						return true;
					}
				}
			}
		}
		return false;
	}
	
	/**
	 * 判断文件是否为图片文件格式, bmp|gif|jpg|jpeg|png 后缀的图片文件返回true
	 * @param imageName 图片文件名
	 * @return
	 */
	public static boolean isImageByFileName(String imageName) {
		if (StringUtils.isNotEmpty(imageName)) {
			String[] imageNames = imageName.split(FILE_CONNECTOR_POINT);
			return isImageBySuffix(imageNames[imageNames.length - 1]);
		}
		return false;
	}
	
	/**
	 * 判断文件是否为合法图片
	 * @param srcPath 图片文件绝对路径
	 * @param checkImageName 是否校验图片文件名
	 * @return
	 */
	public static boolean isImage(String srcPath, boolean checkImageName) {
		if (checkImageName) {
			return isImageByFileName(srcPath);
		} else {
			if (StringUtils.isNotEmpty(srcPath)) {
				File imageFile = new File(srcPath);
				if (imageFile.isFile() && imageFile.length() > 0) {
					return isImage(imageFile);
				}
			}
		}
		return false;
	}
	
	/**
	 * 判断文件流是否为合法图片
	 * @param file 图片文件
	 * @return
	 */
	public static boolean isImage(File file) {
		return isImage((Object)file);
	}
	
	/**
	 * 判断文件流是否为合法图片
	 * @param srcInputStream 图片文件的流
	 * @return
	 */
	public static boolean isImage(InputStream srcInputStream) {
		return isImage((Object)srcInputStream);
	}
	
	/**
	 * 判断文件流是否为合法图片
	 * @param srcInputStream 图片文件的流
	 * @return
	 */
	public static boolean isImage(URL url) {
		return isImage((Object)url);
	}
	
	/**
	 * 图片文件读取
	 * @param obj (URL|InputStream|File)
	 * @return
	 */
	private static boolean isImage(Object obj) {
		Image image = null;
		if (obj != null) {
			try {
				if (obj instanceof URL) {
					image = ImageIO.read((URL)obj);
				} else if (obj instanceof InputStream) {
					image = ImageIO.read((InputStream)obj);
				} else if (obj instanceof File) {
					image = ImageIO.read((File)obj);
				} else {
					throw new IllegalArgumentException("不支持这种类型["+obj.getClass().getCanonicalName()+"]");
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (image != null && image.getWidth(null) > 0 && image.getHeight(null) > 0) {
				return true;
			}
		}
		return false;
	}

/**
	 * 获取图片类型
	 * JPG图片头信息:FFD8FF
	 * PNG图片头信息:89504E47
	 * GIF图片头信息:47494638
	 * BMP图片头信息:424D
	 * 
	 * @param is 图片文件流
	 * @return 图片类型:jpg|png|gif|bmp
	 */
	public static String getImageType(InputStream is) {
		String type = null;
		if (is != null) {
			byte[] b = new byte[4];
			try {
				is.read(b, 0, b.length);
			} catch (IOException e) {
				e.printStackTrace();
			}
			String hexStr = HexConverter.byteArrayToHexString(b, true);//图片文件流前4个字节的头信息（子文字母）
			if (hexStr != null) {
				if (hexStr.startsWith(JPG_HEX)) {
					type = JPG;
				} else if (hexStr.startsWith(PNG_HEX)) {
					type = PNG;
				} else if (hexStr.startsWith(GIF_HEX)) {
					type = GIF;
				} else if (hexStr.startsWith(BMP_HEX)) {
					type = BMP;
				}
			}
		}
		return type;
	}
	
	/**
	 * 获取图片类型
	 * JPG图片头信息:FFD8FF
	 * PNG图片头信息:89504E47
	 * GIF图片头信息:47494638
	 * BMP图片头信息:424D
	 * 
	 * @param file 图片文件
	 * @return 图片类型:jpg|png|gif|bmp
	 * @throws FileNotFoundException 未找到文件
	 */
	public static String getImageType(File file) throws FileNotFoundException {
		return getImageType(new FileInputStream(file));
	}
	
	/**
	 * 根据文件头，判断文件流是否为合法图片
	 * @param is 文件流
	 * @return
	 */
	public static boolean isImageByHeader(InputStream is) {
		return isImageBySuffix(getImageType(is));
	}
	
	/**
	 * 根据文件头，判断文件流是否为合法图片
	 * @param file 图片文件
	 * @return
	 * @throws FileNotFoundException 
	 */
	public static boolean isImageByHeader(File file) throws FileNotFoundException {
		return isImageBySuffix(getImageType(file));
	}

测试代码

    /**
	 * 测试文件是否为图片
	 * @throws FileNotFoundException 
	 * @throws MalformedURLException 
	 */
	@SuppressWarnings("resource")
	@Test
	public void testIsImage() throws FileNotFoundException, MalformedURLException {
		String imageName = "simple.jpg";
		String srcPath = IMAGE_PATH + imageName;
		Assert.assertTrue(ImageUtil.isImage(srcPath, true));
		
		Assert.assertTrue(ImageUtil.isImage(new File(srcPath)));
		
		Assert.assertTrue(ImageUtil.isImage(new FileInputStream(srcPath)));
		
		String baiduLogoUrl = "https://www.baidu.com/img/bd_logo1.png";//百度logo图片
		Assert.assertTrue(ImageUtil.isImage(new URL(baiduLogoUrl)));
		
		String textName = "text.txt";
		String txtPath = FILE_PATH + textName;
		Assert.assertFalse(ImageUtil.isImage(txtPath, true));
	}

    @SuppressWarnings("resource")
	@Test
	public void testIsImageByHeader() throws FileNotFoundException {
		String imageName = "simple.jpg";
		String srcPath = IMAGE_PATH + imageName;
		Assert.assertTrue(ImageUtil.isImageByHeader(new FileInputStream(srcPath)));
		
		imageName = "bd_logo1.png";
		srcPath = IMAGE_PATH + imageName;
		Assert.assertTrue(ImageUtil.isImageByHeader(new File(srcPath)));
		
		imageName = "simple.bmp";
		srcPath = IMAGE_PATH + imageName;
		Assert.assertTrue(ImageUtil.isImageByHeader(new File(srcPath)));
		
		imageName = "simple.gif";
		srcPath = IMAGE_PATH + imageName;
		Assert.assertTrue(ImageUtil.isImageByHeader(new File(srcPath)));
	}

完整源码：https://github.com/ConstXiong/xtools

【Java面试题与答案】整理推荐

• 基础与语法
• 集合
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• 并发编程
• Web
• 安全
• 设计模式
• 框架
• 算法与数据结构
• 异常
• 文件解析与生成
• Linux
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• Dubbo

Java修改图片格式

Java修改图片格式，支持bmp|gif|jpg|jpeg|png之间的转换

工具代码

/**
	 * 修改原图的文件格式
	 * @param srcPath 原图路径
	 * @param destPath 新图路径
	 * @param formatName 图片格式，支持bmp|gif|jpg|jpeg|png
	 * @return
	 */
	public static boolean modifyImageFormat(String srcPath, String destPath, String formatName) {
		boolean isSuccess = false;
		InputStream fis = null;
		try {
			fis = new FileInputStream(srcPath); 
			BufferedImage bufferedImg = ImageIO.read(fis);
			isSuccess = ImageIO.write(bufferedImg, formatName, new File(destPath));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if (fis != null) {
				try {
					fis.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		return isSuccess;
	}

测试代码

/**
	 * 测试修改图片格式
	 * @throws FileNotFoundException
	 */
	@Test
	public void testModifyImageFormat() throws FileNotFoundException {
		String imageName = "java_coffee.jpg";
		String srcPath = IMAGE_PATH + imageName;
		
		imageName = "java_coffee_midify.gif";
		String destPath = IMAGE_PATH + imageName;
		Assert.assertTrue(ImageUtil.modifyImageFormat(srcPath, destPath, "gif"));
		
		Assert.assertEquals(ImageUtil.getImageType(new File(destPath)),  "gif");
	}

 完整源码：https://github.com/ConstXiong/xtools

【Java面试题与答案】整理推荐

• 基础与语法
• 集合
• 网络编程
• 并发编程
• Web
• 安全
• 设计模式
• 框架
• 算法与数据结构
• 异常
• 文件解析与生成
• Linux
• MySQL
• Oracle
• Redis
• Dubbo