1背景
查看各种文章，发现thumbnailator的压缩率和压缩效果都不错，thumbnailator又是使用java实现的，所以直接扒源码，找到了里面实现压缩的关键代码，封装成一个压缩工具类，有需要的同学可以参考。thumbnailator里面有用到很多不错的设计模式，后期也会开相应的模块来介绍。
2 使用方法
2.1 如需要解析jpeg图片颜色模式为CMYK的图片,需要导入依赖
<dependency><groupId>com.twelvemonkeys.imageiogroupId><artifactId>imageio-jpegartifactId><version>3.6version>dependency>2.1 工具类使用
将目录图片下的所有能压缩的图片使用中等质量压缩到目录图片3,文件名保持不变,输出格式为jpg
String source = "E:\\图片压缩\\图片";String traget = "E:\\图片压缩\\图片3";// 压缩图片目录下的所有ThumbnailUtil.of(new File(source).listFiles(ThumbnailUtil.readFilter())).identifyCompress(ThumbnailUtil.ratios[1]) .outputFormat("jpg").toFiles(new File(traget), null);将目录图片下的所有能压缩的图片使用尺寸不变,质量压缩50%压缩到目录图片3,文件名和格式使用原有输入的文件名和格式输出
String source = "E:\\图片压缩\\图片";String traget = "E:\\\图片压缩\\图片3";ThumbnailUtil.of(new File(source).listFiles(ThumbnailUtil.readFilter())).scale(1D).outputQuality(0.5D) .outputFormat(ThumbnailUtil.orgForm).toFiles(new File(traget), "");将图片目录下的原图.jpg使用中等质量压缩到目录图片3,文件名和格式使用原有输入的文件名和格式输出
String source = "E:\\图片压缩\\图片\\原图.jpg";String traget = "E:\\图片压缩\\图片3\\原图.jpg";// 压缩图片目录下的所有ThumbnailUtil.of(new File(source)).identifyCompress(ThumbnailUtil.ratios[1]) .toFile(new File(traget));将图片目录下的原图.jpg使用尺寸不压缩,质量压缩到到目标图片40%质量,文件名和格式使用输入的文件名和格式输出
String source = "E:\\图片压缩\\图片\\原图.jpg";String traget = "E:\\图片压缩\\图片3\\原图.jpg";ThumbnailUtil.of(new File(source)).scale(1D).outputQuality(0.4D)将MultipartFile格式的多张图片进行压缩，使用最高质量压缩（尺寸不变，图片质量为原来的0.8）到目录图片3,文件名和格式使用原有输入的文件名和格式输出MultipartFile格式文件（使用该方法最好使用MimetypesFileTypeMap识别一下多个图片格式是否全部为图片，只压缩图片）
MultipartFile[] myFiles = ThumbnailUtil.of(myFiles) .identifyCompress(ThumbnailUtil.ratios[0]) .outputFormat(ThumbnailUtil.orgForm).asMultipartFiles();2.2 压缩效果
原图尺寸3840*2400，图片大小1311KB：
压缩比率identifyCompress选low低压缩率，尺寸3840*2400，图片大小1025KB
压缩比率identifyCompress选medium中等压缩率，尺寸3072*1920，图片大小491KB
压缩比率identifyCompress选high高压缩率，尺寸2688*1680，图片大小317KB
2.2 压缩工具类
import org.apache.commons.lang3.StringUtils;import org.springframework.mock.web.MockMultipartFile;import org.springframework.web.multipart.MultipartFile;import javax.activation.MimetypesFileTypeMap;import javax.imageio.*;import javax.imageio.stream.ImageOutputStream;import java.awt.*;import java.awt.image.BufferedImage;import java.io.*;import java.util.List;import java.util.*;import java.util.stream.StreamSupport;public class ThumbnailUtil { // 压缩比率, 低(原质量*0.85),中(原质量*0.7),高(原质量*0.6) public static String[] ratios = new String[]{"low", "medium", "high"}; // 原始格式 public static String orgForm = "orgForm"; public static Builder<File> of(File... files) { Iterable<File> iter = Arrays.asList(files); return new Builder<>(iter); } public static Builder<BufferedImage> of(BufferedImage... images) { return new Builder<>(Arrays.asList(images)); } public static Builder<InputStream> of(InputStream... inputStreams) { return new Builder<>(Arrays.asList(inputStreams)); } public static Builder<MultipartFile> of(MultipartFile... multipartFiles) { return new Builder<>(Arrays.asList(multipartFiles)); } public static FilenameFilter readFilter() { String readFormats[] = ImageIO.getReaderFormatNames(); Set<String> readFormatSet = new HashSet<>(Arrays.asList(readFormats)); String writeFormats[] = ImageIO.getWriterFormatNames(); return new FilenameFilter() { @Override public boolean accept(File dir, String name) { String seprator = "."; if (name == null || !name.contains(seprator)) { return false; } String format = name.substring(name.lastIndexOf(seprator) + 1); return readFormatSet.contains(format); } }; } public static class Builder<T> { // 待转换源数据 private final Iterable<T> sources; // 输出格式 private String outputFormat = null; // // 原图宽// private int width = -1;// // 原图高// private int height = -1; // 压缩比率 private String compressionRatio = null; // 缩放后宽 private double scaleWidth = Double.NaN; // 缩放后高 private double scaleHeight = Double.NaN; // 压缩质量系数 0-1之间 private double outputQuality = Double.NaN; private Builder() { sources = null; } private Builder(Iterable<T> sources) { this.sources = sources; } public Builder<T> identifyCompress(String compressionRatio) { if (!Objects.equals(Double.NaN, scaleWidth) || !Objects.equals(Double.NaN, scaleHeight) || !Objects.equals(Double.NaN, outputQuality) ) { // 有设置scale和outputQuality则不使用自动压缩选项 return this; } else if (null == compressionRatio) { this.compressionRatio = ratios[1]; return this; } if (!Arrays.toString(ratios).contains(compressionRatio)) { throw new IllegalArgumentException("Unsupported compressionRatio Type."); } this.compressionRatio = compressionRatio; return this; } private Builder<T> identifyCompress(String compressionRatio, int width, int height) { if (width <= 0 || height <= 0) { throw new IllegalArgumentException("Width (" + width + ") and height (" + height + ") cannot be <= 0"); } // 为了支持多线程压缩, 需要将可变变量直接传入方法中,不能使用共享变量返回scaleWidth和outputQuality if (!Objects.equals(Double.NaN, scaleWidth) || !Objects.equals(Double.NaN, scaleHeight) || !Objects.equals(Double.NaN, outputQuality) ) { // 有设置scale和outputQuality则不使用自动压缩选项 return this; } else if (null == compressionRatio) { compressionRatio = ratios[1]; } if (!Arrays.toString(ratios).contains(compressionRatio)) { throw new IllegalArgumentException("Unsupported compressionRatio Type."); } int min = width < height ? width : height; double offset; Builder builder = new Builder(); if (Objects.equals(ratios[0], compressionRatio)) { // 最低压缩,图片保持原来尺寸,质量为原来的0.8 builder.scaleWidth = builder.scaleHeight = 1.0D; builder.outputQuality = 0.8D; return builder; } else if (Objects.equals(ratios[1], compressionRatio)) { offset = 0.4D; } else { offset = 0.3D; } if (min <= 1024) { // 最小像素小于1024,长和宽不压缩 builder.scaleWidth = builder.scaleHeight = 1.0D; builder.outputQuality = (builder.outputQuality = 0.3D + offset) <= 1 ? builder.outputQuality : 1; } else if (min > 1024 && min <= 3 * 1024) { builder.scaleHeight = (builder.scaleHeight = 0.4D + offset) <= 1 ? builder.scaleHeight : 1; builder.scaleWidth = builder.scaleHeight; builder.outputQuality = (builder.outputQuality = 0.3D + offset) <= 1 ? builder.outputQuality : 1; } else { builder.scaleHeight = (builder.scaleHeight = 2048D / min + offset) <= 1 ? builder.scaleHeight : 1; builder.scaleWidth = builder.scaleHeight; builder.outputQuality = builder.scaleHeight; } return builder; } public Builder<T> scale(double scaleWidth, double scaleHeight) { if (scaleWidth <= 0.0 || scaleHeight <= 0.0) { throw new IllegalArgumentException( "The scaling factor is equal to or less than 0." ); } if (Double.isNaN(scaleWidth) || Double.isNaN(scaleHeight)) { throw new IllegalArgumentException( "The scaling factor is not a number." ); } if (Double.isInfinite(scaleWidth) || Double.isInfinite(scaleHeight)) { throw new IllegalArgumentException( "The scaling factor cannot be infinity." ); } this.scaleWidth = scaleWidth; this.scaleHeight = scaleHeight; return this; } public Builder<T> scale(double scale) { return scale(scale, scale); } public Builder<T> outputQuality(double quality) { if (quality < 0.0f || quality > 1.0f) { throw new IllegalArgumentException( "The quality setting must be in the range 0.0f and " + "1.0f, inclusive." ); } outputQuality = quality; return this; } public Builder<T> outputFormat(String formatName) { if (StringUtils.isEmpty(formatName)) { this.outputFormat = orgForm; return this; } else if (Objects.equals(orgForm, formatName)) { this.outputFormat = formatName; return this; } Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName(formatName); if (!writers.hasNext()) { throw new UnsupportedOperationException( "No suitable ImageWriter found for " + formatName + "." ); } this.outputFormat = formatName; return this; } private String outputFormat(T source, String formatName) throws IOException { if (source == null) { throw new IllegalArgumentException("The resource being processed is null."); } if (StringUtils.isEmpty(formatName)) { formatName = orgForm; } else if (!Objects.equals(orgForm, formatName)) { return formatName; } Iterator<ImageReader> iterReader = ImageIO.getImageReaders(ImageIO.createImageInputStream(source)); if (null == iterReader || !iterReader.hasNext()) { throw new UnsupportedOperationException("The resource being processed is not a picture."); } formatName = iterReader.next().getFormatName(); Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName(formatName); if (!writers.hasNext()) { throw new UnsupportedOperationException( "No suitable ImageWriter found for " + formatName + "." ); } return formatName; } private void write(T source, final ImageOutputStream outputStream) throws IOException { if (StringUtils.isEmpty(outputFormat)) { throw new IllegalStateException("Output format has not been set."); } Objects.requireNonNull(outputStream, "Could not open OutputStream."); BufferedImage srcImage; if (source instanceof BufferedImage) { srcImage = (BufferedImage) source; } else if (source instanceof File) { srcImage = ImageIO.read((File) source); } else if (source instanceof MultipartFile) { srcImage = ImageIO.read(((MultipartFile) source).getInputStream()); // 将MultipartFile装换为InputStream source = (T) ((MultipartFile) source).getInputStream(); } else if (source instanceof InputStream) { srcImage = ImageIO.read((InputStream) source); } else { throw new IllegalArgumentException("Unsupported ImageIO Type."); } String outputFormatName = this.outputFormat(source, outputFormat); System.out.println("outputFormatName : " + outputFormatName); // 原图宽 int width = srcImage.getWidth(); // 原图高 int height = srcImage.getHeight(); // 如果没有设置宽高和压缩比,则自动识别最佳压缩比 Builder builder = this.identifyCompress(compressionRatio, width, height); double scaleWidth = builder.scaleWidth; double scaleHeight = builder.scaleHeight; double outputQuality = builder.outputQuality; System.out.println("scaleWidth ; " + scaleWidth + " scaleHeight : " + scaleHeight + " outputQuality : " + outputQuality); if (Objects.equals(outputQuality, Double.NaN)) { throw new IllegalArgumentException("outputQuality is null."); } // 缩放后宽 int sclWidth = Objects.equals(Double.NaN, scaleWidth) ? width : (int) (width * scaleWidth); // 缩放后高 int sclHeight = Objects.equals(Double.NaN, scaleHeight) ? height : (int) (height * scaleHeight); System.out.println("sclWidth : " + sclWidth + " sclHeight : " + sclHeight);// Image from = srcImage.getScaledInstance(width, height, Image.SCALE_AREA_AVERAGING); // 输出BufferedImage流 long startTime = System.currentTimeMillis(); BufferedImage destImage = new BufferedImage(sclWidth, sclHeight, BufferedImage.TYPE_INT_RGB); Graphics2D g = destImage.createGraphics(); // 消除锯齿 g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);// g.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL,RenderingHints.VALUE_STROKE_DEFAULT); g.addRenderingHints(new HashMap<>()); g.drawImage(srcImage, 0, 0, sclWidth, sclHeight, null); System.out.println("image scale cost time : " + (System.currentTimeMillis() - startTime)); // 压缩后增加一点点锐化,如不需要的,以下4行代码可以干掉 // 拉普拉斯边缘锐化// startTime = System.currentTimeMillis();// BufferedImage imageSharpen = ImageSharpen.lapLaceSharpDeal(destImage);// System.out.println("lapLaceSharpDeal cost time : " + (System.currentTimeMillis() - startTime));// //设置为透明覆盖// g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, 0.2f));// //在背景图片上添加锐化的边缘// g.drawImage(imageSharpen, 0, 0, imageSharpen.getWidth(), imageSharpen.getHeight(), null);// // 释放对象 透明度设置结束// g.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER)); g.dispose(); ImageWriter writer = null; ImageTypeSpecifier type = ImageTypeSpecifier.createFromRenderedImage(destImage); // formatName不生效, 所以统一使用jpg// Iterator iterIO = ImageIO.getImageWriters(type, outputFormatName); Iterator iterIO = ImageIO.getImageWriters(type, "jpg"); if (iterIO.hasNext()) { writer = (ImageWriter) iterIO.next(); } if (writer == null) { throw new IllegalArgumentException("ImageWriter is null."); } IIOImage iioImage = new IIOImage(destImage, null, null); ImageWriteParam param = writer.getDefaultWriteParam(); if (param.canWriteCompressed() && !outputFormatName.equalsIgnoreCase("bmp")) { param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); param.setCompressionQuality((float) outputQuality); //这里可以指定压缩的程度 0-1.0 } else {// param.setCompressionQuality(0.0f); System.out.println("The outputFormat (" + outputFormatName + ") cannot be compressed"); }// ImageOutputStream outputStream = ImageIO.createImageOutputStream(os);// if (outputStream == null) {// throw new IOException("Could not open OutputStream.");// } writer.setOutput(outputStream); writer.write(null, iioImage, param); writer.dispose(); outputStream.close(); } public ByteArrayInputStream asByteArray() throws IOException { Iterator<T> iter = sources.iterator(); T source = iter.next(); if (iter.hasNext()) { throw new IllegalArgumentException("Cannot create one thumbnail from multiple original images."); } // 将缓存中的图片按照指定的配置输出到字节数组中 ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); write(source, ImageIO.createImageOutputStream(byteArrayOutputStream)); // 从字节数组中读取图片 ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArrayOutputStream.toByteArray());// InputStream inputStream = new ByteArrayInputStream(byteArrayInputStream);// MultipartFile file = new MockMultipartFile(ContentType.APPLICATION_OCTET_STREAM.toString(), byteArrayInputStream); return byteArrayInputStream; } public MultipartFile[] asMultipartFiles() { long startTime = System.currentTimeMillis(); MultipartFile[] multipartFiles = StreamSupport.stream(sources.spliterator(), true).map(source -> { if (!(source instanceof File) && (!(source instanceof MultipartFile)) ) { throw new IllegalStateException("Cannot create thumbnails to files if original images are not from files or multipartFile."); } String filename = ""; String mimeType = ""; if (source instanceof File) { filename = ((File) source).getName(); MimetypesFileTypeMap fileTypeMap = new MimetypesFileTypeMap(); mimeType = fileTypeMap.getContentType(filename); } else if (source instanceof MultipartFile) { filename = ((MultipartFile) source).getOriginalFilename(); mimeType = ((MultipartFile) source).getContentType(); } // 将缓存中的图片按照指定的配置输出到字节数组中 ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); try { System.out.println("Process the image " + filename + " start."); write(source, ImageIO.createImageOutputStream(byteArrayOutputStream)); } catch (IOException e) { String desc = "Failed to process the image " + filename + " ."; System.out.println(desc); throw new IllegalArgumentException(desc, e); } // 从字节数组中读取图片 ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArrayOutputStream.toByteArray()); String octetStream = "application/octet-stream"; MultipartFile multipartFile = null; try { multipartFile = new MockMultipartFile(octetStream, filename, mimeType, byteArrayInputStream); } catch (IOException e) { String desc = "Failed to mockMultipartFile the image " + filename + " ."; System.out.println(desc); throw new IllegalArgumentException(desc, e); } return multipartFile; }).toArray(MultipartFile[]::new); System.out.println("cost : " + (System.currentTimeMillis() - startTime)); return multipartFiles; } public void toFile(final File outFile) throws IOException { Iterator<T> iter = sources.iterator(); T source = iter.next(); if (iter.hasNext()) { throw new IllegalArgumentException("Cannot create one thumbnail from multiple original images."); } write(source, ImageIO.createImageOutputStream(outFile)); } private void toFiles(Iterable<File> iterable) throws IOException { Iterator<File> filenameIter = iterable.iterator(); for (T source : sources) { if (!filenameIter.hasNext()) { throw new IndexOutOfBoundsException("Not enough file names provided by iterator." ); } write(source, ImageIO.createImageOutputStream(filenameIter.next())); } } public void toFiles(File destinationDir, String namePrefix) throws IOException { if (destinationDir == null && namePrefix == null) { throw new NullPointerException("destinationDir and rename is null."); } if (destinationDir != null && !destinationDir.isDirectory()) { destinationDir.mkdir();// throw new IllegalArgumentException("Given destination is not a directory."); } if (destinationDir != null && !destinationDir.isDirectory()) { throw new IllegalArgumentException("Given destination is not a directory."); } long startTime = System.currentTimeMillis(); Builder<T> builder = outputFormat(outputFormat); StreamSupport.stream(sources.spliterator(), true).forEach(source -> { if (!(source instanceof File)) { throw new IllegalStateException("Cannot create thumbnails to files if original images are not from files."); } File f = (File) source; File actualDestDir = destinationDir == null ? f.getParentFile() : destinationDir; String name = StringUtils.isEmpty(namePrefix) ? f.getName() : namePrefix + f.getName(); if (!Objects.equals(orgForm, builder.outputFormat)) { name = name.substring(0, name.lastIndexOf(".")) + "." + outputFormat; } File destinationFile = new File(actualDestDir, name); try { System.out.println("Process the image " + f.getName() + " start."); write((T) source, ImageIO.createImageOutputStream(destinationFile)); } catch (Exception e) { System.out.println("Failed to process the image " + f.getName() + " ."); e.printStackTrace(); } }); System.out.println("cost : " + (System.currentTimeMillis() - startTime)); } public void toOutputStream(final OutputStream outputStream) throws IOException { Iterator<T> iter = sources.iterator(); T source = iter.next(); if (iter.hasNext()) { throw new IllegalArgumentException("Cannot create one thumbnail from multiple original images."); } write(source, ImageIO.createImageOutputStream(outputStream)); } public void toOutputStreams(Iterable<? extends OutputStream> iterable) throws IOException { Iterator<? extends OutputStream> filenameIter = iterable.iterator(); for (T source : sources) { if (!filenameIter.hasNext()) { throw new IndexOutOfBoundsException("Not enough file names provided by iterator." ); } write(source, ImageIO.createImageOutputStream(filenameIter.next())); } } } 参考：
thumbnailator的github地址
java使用google开源工具实现图片压缩
[Java]图片压缩
byte数组、Blob、inputStream、outputStream、MultipartFile之间的转换
来源地址：https://blog.csdn.net/Master_Shifu_/article/details/128676860
