想必你碰到这些情况：

哈哈大部分我们都会去干嘛呢？

作为计算机学者啊肯定会想到一些这些坑爹收费的垃圾东西我们自己搞搞
其实这不就是我们经常写过的文件上传下载业务吗
参考：https://www.cnblogs.com/gaodiyuanjin/p/18410900
结合博客园博主与统义灵码结合

 图片插件依赖
        <dependency>
            <groupId>net.coobird</groupId>
            <artifactId>thumbnailator</artifactId>
            <version>0.4.20</version>
        </dependency>

 前页面显示：
<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>图片上传和下载</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
            background-color: #f4f4f9;
        }
        .container {
            text-align: center;
            background: white;
            padding: 20px;
            border-radius: 8px;
            box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
        }
        button {
            margin: 10px;
            padding: 10px 20px;
            font-size: 16px;
            cursor: pointer;
        }
    </style>
</head>
<body>
    <div class="container">
        <h1>图片上传和下载</h1>
        <button id="uploadButton">上传图片</button>
        <button id="downloadButton">下载图片</button>
        <input type="file" id="fileInput" style="display:none;" accept="image/*">
        <img id="previewImage" src="" alt="预览图片" style="display:none; max-width: 300px; margin-top: 20px;">
    </div>
 
    <script>
        document.getElementById('uploadButton').addEventListener('click', function() {
            document.getElementById('fileInput').click();
        });
 
        document.getElementById('fileInput').addEventListener('change', function(event) {
            const file = event.target.files[0];
            if (file) {
                const formData = new FormData();
                formData.append('file', file);
 
                fetch('/api/images/upload', {
                    method: 'POST',
                    body: formData
                })
                .then(response => response.text())
                .then(message => {
                    alert(message);
                    if (message === "图片上传成功") {
                        const reader = new FileReader();
                        reader.onload = function(e) {
                            const img = document.getElementById('previewImage');
                            img.src = e.target.result;
                            img.style.display = 'block';
                        };
                        reader.readAsDataURL(file);
                    }
                })
                .catch(error => console.error('Error:', error));
            }
        });
 
        document.getElementById('downloadButton').addEventListener('click', function() {
            const img = document.getElementById('previewImage');
            if (img.src) {
                const filename = img.src.split('/').pop();
                window.location.href = `/api/images/download/${filename}`;
            } else {
                alert('请先上传图片');
            }
        });
    </script>
</body>
</html>

 业务controller
package com.example.demo;
 
import net.coobird.thumbnailator.Thumbnails;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
 
import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.stream.ImageOutputStream;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Iterator;
 
@RestController
@RequestMapping("/api/images")
public class ImageController {
    private static final String UPLOAD_DIR = "D:/zhaowenya/";
    private static final int MAX_WIDTH = 380; // 最大宽度
    private static final int MAX_HEIGHT = 640; // 最大高度
 
    @PostMapping("/upload")
    public ResponseEntity<String> uploadImage(@RequestParam("file") MultipartFile file) {
        try {
            if (file.isEmpty()) {
                return ResponseEntity.badRequest().body("请选择一个文件");
            }
 
            // 检查文件类型
            if (!file.getContentType().startsWith("image")) {
                return ResponseEntity.badRequest().body("文件类型不支持");
            }
 
            // 读取图片
            BufferedImage originalImage = ImageIO.read(file.getInputStream());
 
            // 调整图片大小
            BufferedImage resizedImage = Thumbnails.of(originalImage)
                    .size(MAX_WIDTH, MAX_HEIGHT)
                    .keepAspectRatio(false) // 不保持宽高比
                    .outputFormat("jpg") // 指定输出格式
                    .asBufferedImage();
 
            // 压缩图片到指定大小
            File destFile = new File(UPLOAD_DIR, file.getOriginalFilename());
            compressImageToSize(resizedImage, destFile, 20 * 1024); // 20 KB
 
            return ResponseEntity.ok("图片上传成功");
        } catch (IOException e) {
            e.printStackTrace();
            return ResponseEntity.status(500).body("上传失败");
        }
    }
 
    @GetMapping("/download/{filename}")
    public ResponseEntity<Resource> downloadImage(@PathVariable String filename) {
        try {
            File file = new File(UPLOAD_DIR + filename);
            if (!file.exists()) {
                return ResponseEntity.notFound().build();
            }
 
            Resource resource = new FileSystemResource(file);
 
            return ResponseEntity.ok()
                    .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + resource.getFilename() + "\"")
                    .contentType(MediaType.IMAGE_JPEG) // 根据实际情况调整媒体类型
                    .body(resource);
        } catch (Exception e) {
            e.printStackTrace();
            return ResponseEntity.status(500).body(null);
        }
    }
 
    private void compressImageToSize(BufferedImage image, File destFile, int targetSizeInBytes) throws IOException {
        float quality = 1.0f; // 初始质量
        float minQuality = 0.1f; // 最小质量
        float maxQuality = 1.0f; // 最大质量
 
        byte[] compressedImageBytes;
        do {
            compressedImageBytes = compressImage(image, quality);
            quality -= 0.1f; // 减少质量以减小文件大小
        } while (compressedImageBytes.length > targetSizeInBytes && quality >= minQuality);
 
        if (compressedImageBytes.length > targetSizeInBytes) {
            throw new IOException("无法将图片压缩到指定大小");
        }
 
        try (FileOutputStream fos = new FileOutputStream(destFile)) {
            fos.write(compressedImageBytes);
        }
    }
 
    private byte[] compressImage(BufferedImage image, float quality) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("jpg");
        if (!writers.hasNext()) {
            throw new IOException("不支持的图片格式");
        }
        ImageWriter writer = writers.next();
        ImageWriteParam param = writer.getDefaultWriteParam();
        param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
        param.setCompressionQuality(quality);
 
        try (ImageOutputStream ios = ImageIO.createImageOutputStream(baos)) {
            writer.setOutput(ios);
            writer.write(null, new IIOImage(image, null, null), param);
        } finally {
            writer.dispose();
        }
 
        return baos.toByteArray();
    }
}

通过上述你可以自定义去修改一些什么kb 宽高保存位置图片格式啊什么的
其实这些业务从来都是“大自然的搬运工” 只不过需要的是你持续不断愿意学习能力

posted on 2024-12-05 10:25 不爱美女爱辣条阅读(6) 评论(0) 编辑收藏举报

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	图片插件依赖
	<dependency>
	<groupId>net.coobird</groupId>
	<artifactId>thumbnailator</artifactId>
	<version>0.4.20</version>
	</dependency>

	前页面显示：
	<!DOCTYPE html>
	<html lang="zh-CN">
	<head>
	<meta charset="UTF-8">
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	<title>图片上传和下载</title>
	<style>
	body {
	font-family: Arial, sans-serif;
	display: flex;
	justify-content: center;
	align-items: center;
	height: 100vh;
	background-color: #f4f4f9;
	}
	.container {
	text-align: center;
	background: white;
	padding: 20px;
	border-radius: 8px;
	box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
	}
	button {
	margin: 10px;
	padding: 10px 20px;
	font-size: 16px;
	cursor: pointer;
	}
	</style>
	</head>
	<body>
	<div class="container">
	<h1>图片上传和下载</h1>
	<button id="uploadButton">上传图片</button>
	<button id="downloadButton">下载图片</button>
	<input type="file" id="fileInput" style="display:none;" accept="image/*">
	<img id="previewImage" src="" alt="预览图片" style="display:none; max-width: 300px; margin-top: 20px;">
	</div>

	<script>
	document.getElementById('uploadButton').addEventListener('click', function() {
	document.getElementById('fileInput').click();
	});

	document.getElementById('fileInput').addEventListener('change', function(event) {
	const file = event.target.files[0];
	if (file) {
	const formData = new FormData();
	formData.append('file', file);

	fetch('/api/images/upload', {
	method: 'POST',
	body: formData
	})
	.then(response => response.text())
	.then(message => {
	alert(message);
	if (message === "图片上传成功") {
	const reader = new FileReader();
	reader.onload = function(e) {
	const img = document.getElementById('previewImage');
	img.src = e.target.result;
	img.style.display = 'block';
	};
	reader.readAsDataURL(file);
	}
	})
	.catch(error => console.error('Error:', error));
	}
	});

	document.getElementById('downloadButton').addEventListener('click', function() {
	const img = document.getElementById('previewImage');
	if (img.src) {
	const filename = img.src.split('/').pop();
	window.location.href = `/api/images/download/${filename}`;
	} else {
	alert('请先上传图片');
	}
	});
	</script>
	</body>
	</html>

	业务controller
	package com.example.demo;

	import net.coobird.thumbnailator.Thumbnails;
	import org.springframework.core.io.FileSystemResource;
	import org.springframework.core.io.Resource;
	import org.springframework.http.HttpHeaders;
	import org.springframework.http.MediaType;
	import org.springframework.http.ResponseEntity;
	import org.springframework.web.bind.annotation.*;
	import org.springframework.web.multipart.MultipartFile;

	import javax.imageio.IIOImage;
	import javax.imageio.ImageIO;
	import javax.imageio.ImageWriteParam;
	import javax.imageio.ImageWriter;
	import javax.imageio.stream.ImageOutputStream;
	import java.awt.image.BufferedImage;
	import java.io.ByteArrayOutputStream;
	import java.io.File;
	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.util.Iterator;

	@RestController
	@RequestMapping("/api/images")
	public class ImageController {
	private static final String UPLOAD_DIR = "D:/zhaowenya/";
	private static final int MAX_WIDTH = 380; // 最大宽度
	private static final int MAX_HEIGHT = 640; // 最大高度

	@PostMapping("/upload")
	public ResponseEntity<String> uploadImage(@RequestParam("file") MultipartFile file) {
	try {
	if (file.isEmpty()) {
	return ResponseEntity.badRequest().body("请选择一个文件");
	}

	// 检查文件类型
	if (!file.getContentType().startsWith("image")) {
	return ResponseEntity.badRequest().body("文件类型不支持");
	}

	// 读取图片
	BufferedImage originalImage = ImageIO.read(file.getInputStream());

	// 调整图片大小
	BufferedImage resizedImage = Thumbnails.of(originalImage)
	.size(MAX_WIDTH, MAX_HEIGHT)
	.keepAspectRatio(false) // 不保持宽高比
	.outputFormat("jpg") // 指定输出格式
	.asBufferedImage();

	// 压缩图片到指定大小
	File destFile = new File(UPLOAD_DIR, file.getOriginalFilename());
	compressImageToSize(resizedImage, destFile, 20 * 1024); // 20 KB

	return ResponseEntity.ok("图片上传成功");
	} catch (IOException e) {
	e.printStackTrace();
	return ResponseEntity.status(500).body("上传失败");
	}
	}

	@GetMapping("/download/{filename}")
	public ResponseEntity<Resource> downloadImage(@PathVariable String filename) {
	try {
	File file = new File(UPLOAD_DIR + filename);
	if (!file.exists()) {
	return ResponseEntity.notFound().build();
	}

	Resource resource = new FileSystemResource(file);

	return ResponseEntity.ok()
	.header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + resource.getFilename() + "\"")
	.contentType(MediaType.IMAGE_JPEG) // 根据实际情况调整媒体类型
	.body(resource);
	} catch (Exception e) {
	e.printStackTrace();
	return ResponseEntity.status(500).body(null);
	}
	}

	private void compressImageToSize(BufferedImage image, File destFile, int targetSizeInBytes) throws IOException {
	float quality = 1.0f; // 初始质量
	float minQuality = 0.1f; // 最小质量
	float maxQuality = 1.0f; // 最大质量

	byte[] compressedImageBytes;
	do {
	compressedImageBytes = compressImage(image, quality);
	quality -= 0.1f; // 减少质量以减小文件大小
	} while (compressedImageBytes.length > targetSizeInBytes && quality >= minQuality);

	if (compressedImageBytes.length > targetSizeInBytes) {
	throw new IOException("无法将图片压缩到指定大小");
	}

	try (FileOutputStream fos = new FileOutputStream(destFile)) {
	fos.write(compressedImageBytes);
	}
	}

	private byte[] compressImage(BufferedImage image, float quality) throws IOException {
	ByteArrayOutputStream baos = new ByteArrayOutputStream();
	Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("jpg");
	if (!writers.hasNext()) {
	throw new IOException("不支持的图片格式");
	}
	ImageWriter writer = writers.next();
	ImageWriteParam param = writer.getDefaultWriteParam();
	param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
	param.setCompressionQuality(quality);

	try (ImageOutputStream ios = ImageIO.createImageOutputStream(baos)) {
	writer.setOutput(ios);
	writer.write(null, new IIOImage(image, null, null), param);
	} finally {
	writer.dispose();
	}

	return baos.toByteArray();
	}
	}