java 图片压缩、缩放

对图像的缩放可以带来很多好处，比如在载入图像时可以有效减少各方面的压力。 
这里依靠thumbnailator、imgscalr这两个jar包分别实现。 
为了能够粗粒度的控制压缩，定义一个ScalrConfig来控制图像尺寸，图像类型(JPG、BMP。。。。)等。

   
   
   
   

    
    
    
    
public class ScalrConfig {
    
    
    
    
	//图片质量
    
    
    
    
	private Float quality = 1F;
    
    
    
    
	//图片高度
    
    
    
    
	private int height = 600;
    
    
    
    
	//图片宽度
    
    
    
    
	private int width = 600;
    
    
    
    
	//使长或宽适应到某一个长度
    
    
    
    
	private Integer size ;
    
    
    
    
	//重写format
    
    
    
    
	private ImageExtensionEnum type = ImageExtensionEnum.JPG;
    
    
    
    
	//是否重写
    
    
    
    
	private boolean retype = true;
    
    
    
    
	//保持横纵比
    
    
    
    
	private boolean aspectRatio = true;
    
    
    
    
	//压缩过滤
    
    
    
    
	private ScalrFilter filter;
    
    
    
    
	
    
    
    
    
	public ScalrConfig(int size,int allowWidth,
    
    
    
    
			int allowHeight){
    
    
    
    
		this.size = size;
    
    
    
    
		this.filter = new DefautlScalrFiter(allowWidth,allowHeight);
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	public ScalrConfig(int width,int height,
    
    
    
    
			int allowWidth,int allowHeight){
    
    
    
    
		this.height = height;
    
    
    
    
		this.width = width;
    
    
    
    
		this.filter = new DefautlScalrFiter(allowWidth,allowHeight);
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	class DefautlScalrFiter implements ScalrFilter{
    
    
    
    
		
    
    
    
    
		private int allowWidth;
    
    
    
    
		
    
    
    
    
		private int allowHeight;
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public boolean doFilter(int _width, int _height) {
    
    
    
    
			return allowWidth < _width || allowHeight < _height;
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		public DefautlScalrFiter(int allowWidth, int allowHeight) {
    
    
    
    
			this.allowWidth = allowWidth;
    
    
    
    
			this.allowHeight = allowHeight;
    
    
    
    
		}
    
    
    
    
	}
    
    
    
    
//省略setter、getter
   
   
   
   

ImageExtensionEnum用来定义图片格式（GIF不支持。。。。）

   
   
   
   

    
    
    
    
public enum ImageExtensionEnum {
    
    
    
    
	
    
    
    
    
	JPG,JPEG,PNG,BMP,GIF;
    
    
    
    
	
    
    
    
    
	public final static String [] getExtensions(){
    
    
    
    
		ImageExtensionEnum enums [] = ImageExtensionEnum.values();
    
    
    
    
		String [] extensions = new String [enums.length];
    
    
    
    
		for(int i=0;i<enums.length;i++)
    
    
    
    
			extensions[i] = enums[i].name();
    
    
    
    
		return extensions;
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	public static boolean isJPG(String extension){
    
    
    
    
		return JPEG.name().equalsIgnoreCase(extension) || 
    
    
    
    
				JPG.name().equalsIgnoreCase(extension);
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	public static boolean isSameType(String extension1,String extension2){
    
    
    
    
    	if(extension1 == null || extension2 == null) return false;
    
    
    
    
    	return (extension1.equalsIgnoreCase(extension2))||
    
    
    
    
    			(isJPG(extension1)&&isJPG(extension2))?true : false;
    
    
    
    
    }
    
    
    
    
}
   
   
   
   

ScalrFilter 用来控制图片是否需要被压缩，如果图片过小，此时缩放是不明智的。

   
   
   
   

    
    
    
    
public interface ScalrFilter {
    
    
    
    
	
    
    
    
    
	public boolean doFilter(int _width,int _height);
    
    
    
    
 
    
    
    
    
}
   
   
   
   

下面是图片压缩:

   
   
   
   

    
    
    
    
public interface Thumbnailer {
    
    
    
    
	
    
    
    
    
	/**
    
    
    
    
	 * 
    
    
    
    
	 * @param is 图片文件流
    
    
    
    
	 * @param size 图片大小
    
    
    
    
	 * @param config 配置
    
    
    
    
	 * @param extension 图片后缀
    
    
    
    
	 * @return
    
    
    
    
	 * @throws Exception
    
    
    
    
	 */
    
    
    
    
	List<ThumbnailResult> createThumbnails(File file,
    
    
    
    
			ScalrConfig...configs) throws Exception;
    
    
    
    
 
    
    
    
    
}
   
   
   
   

thumnailResult 是一个接口，用来控制缩放成文件、写入输出流、返回缩放后的图片类型和大小:

   
   
   
   

    
    
    
    
public interface ThumbnailResult {
    
    
    
    
	
    
    
    
    
	File writeToFile(File destFile) throws Exception;
    
    
    
    
	
    
    
    
    
	void writeToStream(OutputStream stream) throws Exception;
    
    
    
    
	
    
    
    
    
	int getWidth() throws Exception;
    
    
    
    
	
    
    
    
    
	int getHeight() throws Exception;
    
    
    
    
	
    
    
    
    
	String getExtension();
    
    
    
    
 
    
    
    
    
	
    
    
    
    
}
   
   
   
   

最后读取、判断文件：

   
   
   
   

    
    
    
    
public abstract class AbstractThumbaniler implements Thumbnailer{
    
    
    
    
	
    
    
    
    
	@Override
    
    
    
    
	public List<ThumbnailResult> createThumbnails(File file,
    
    
    
    
			ScalrConfig... configs) throws Exception {
    
    
    
    
		if(configs == null || configs.length == 0)
    
    
    
    
		{
    
    
    
    
			throw new IllegalArgumentException("必须指定一个 ScalrConfig");
    
    
    
    
		}	
    
    
    
    
		if (file == null)
    
    
    
    
		{
    
    
    
    
			throw new IllegalArgumentException("文件不能为空");
    
    
    
    
		}
    
    
    
    
		if (!file.exists())
    
    
    
    
		{
    
    
    
    
			throw new IllegalArgumentException(file.getAbsolutePath() + "不存在");
    
    
    
    
		}
    
    
    
    
		String oldExtension = MyStringUtils.getFilenameExtension(file.getName());
    
    
    
    
		if(!isSupportedOutputFormat(oldExtension))
    
    
    
    
		{
    
    
    
    
			throw new IllegalArgumentException("文件不符合格式");
    
    
    
    
		}
    
    
    
    
		BufferedImage image = ImageIO.read(file);
    
    
    
    
		if (image == null)
    
    
    
    
		{
    
    
    
    
			throw new IllegalArgumentException("文件不是一个真正的图片");
    
    
    
    
		}
    
    
    
    
		List<ThumbnailResult> results = new ArrayList<ThumbnailResult>();
    
    
    
    
		for(ScalrConfig config : configs)
    
    
    
    
		{
    
    
    
    
			ScalrFilter filter = config.getFilter();
    
    
    
    
			if(filter == null || (filter != null && 
    
    
    
    
			    filter.doFilter(image.getWidth(), image.getHeight())))
    
    
    
    
			 {
    
    
    
    
				results.add(createThumbnail(image, config,oldExtension));
    
    
    
    
			}
    
    
    
    
		}
    
    
    
    
		return results;
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	abstract ThumbnailResult createThumbnail(BufferedImage image,
    
    
    
    
			ScalrConfig config,String oldExtension) throws Exception;
    
    
    
    
	
    
    
    
    
	protected List<String> getSupportedOutputFormats(){
    
    
    
    
		
    
    
    
    
		String[] formats = ImageIO.getWriterFormatNames();
    
    
    
    
		if (formats == null)
    
    
    
    
		{
    
    
    
    
			return Collections.emptyList();
    
    
    
    
		}
    
    
    
    
		else
    
    
    
    
		{
    
    
    
    
			return Arrays.asList(formats);
    
    
    
    
		}
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	private boolean isSupportedOutputFormat(String format){
    
    
    
    
		for (String supportedFormat : getSupportedOutputFormats())
    
    
    
    
		{
    
    
    
    
			if (supportedFormat.equals(format))
    
    
    
    
			{
    
    
    
    
				return true;
    
    
    
    
			}
    
    
    
    
		}
    
    
    
    
		
    
    
    
    
		return false;
    
    
    
    
	}
    
    
    
    
 
    
    
    
    
}
   
   
   
   

首先是  thumbnailator ，它的使用非常简单！ 
项目地址(请自觉): 
http://code.google.com/p/thumbnailator/  
它能够按照比例缩让、固定尺寸缩放、打水印、旋转和切割等各种的功能，牛逼的是完成这些功能只需要一行代码即可，例如:

   
   
   
   

    
    
    
    
Thumbnails.of(new File("q:/user.bmp")).scale(0.25F).toFile(new File("q:/dest.bmmp"));
    
    
    
    
Thumbnails.of(new File("q:/user.bmp")).size(300, 300).toFile(new File("q:/dest.bmmp"));
    
    
    
    
Thumbnails.of(new File("q:/user.bmp")).size(300,300).
    
    
    
    
                       keepAspectRatio(false).toFile(newFile("q:/dest.bmmp"));
   
   
   
   

下面是具体的使用:

   
   
   
   

    
    
    
    
public class CoobirdThumbnailer extends AbstractThumbaniler {
    
    
    
    
 
    
    
    
    
	@Override
    
    
    
    
	ThumbnailResult createThumbnail(BufferedImage image, ScalrConfig config,
    
    
    
    
			String oldExtension)throws Exception {
    
    
    
    
		int width = image.getWidth();
    
    
    
    
		int height = image.getHeight();
    
    
    
    
		this.calc(config, width, height);
    
    
    
    
		final Builder<BufferedImage> builder = Thumbnails.of(image);
    
    
    
    
		builder.size(config.getWidth(), config.getHeight())
    
    
    
    
				.keepAspectRatio(config.getAspectRatio());
    
    
    
    
		if (config.isRetype())
    
    
    
    
		{
    
    
    
    
			String newExtension = config.getType().name();
    
    
    
    
			if (!ImageExtensionEnum.isSameType(newExtension, oldExtension))
    
    
    
    
				oldExtension = newExtension;
    
    
    
    
		}
    
    
    
    
		builder.outputFormat(oldExtension);
    
    
    
    
		if (ImageExtensionEnum.isJPG(oldExtension)
    
    
    
    
				&& config.getQuality() != null)
    
    
    
    
		{
    
    
    
    
			builder.outputQuality(config.getQuality());
    
    
    
    
		}
    
    
    
    
		return new CoobirdThumbnailResult(builder, oldExtension);
    
    
    
    
	}
    
    
    
    
 
    
    
    
    
	private ScalrConfig calc(ScalrConfig config, int _width, int _height) {
    
    
    
    
		Integer size = config.getSize();
    
    
    
    
		if (size != null) {
    
    
    
    
			config.setAspectRatio(false);
    
    
    
    
			double sourceRatio = (double) _width / (double) _height;
    
    
    
    
			if (_width >= _height)
    
    
    
    
			{
    
    
    
    
				config.setWidth(size);
    
    
    
    
				config.setHeight((int) Math.round(size / sourceRatio));
    
    
    
    
			}
    
    
    
    
			if (_width < _height)
    
    
    
    
			{
    
    
    
    
				config.setHeight(size);
    
    
    
    
				config.setWidth((int) Math.round(size * sourceRatio));
    
    
    
    
			}
    
    
    
    
		}
    
    
    
    
		return config;
    
    
    
    
	}
    
    
    
    
 
    
    
    
    
	private final class CoobirdThumbnailResult implements ThumbnailResult {
    
    
    
    
 
    
    
    
    
		private Builder<BufferedImage> builder;
    
    
    
    
 
    
    
    
    
		private String extension;
    
    
    
    
 
    
    
    
    
		private CoobirdThumbnailResult(Builder<BufferedImage> builder,
    
    
    
    
				String extension) {
    
    
    
    
			super();
    
    
    
    
			this.builder = builder;
    
    
    
    
			this.extension = extension;
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public File writeToFile(File destFile) throws Exception {
    
    
    
    
			String fileName = destFile.getName();
    
    
    
    
			String _extension = MyStringUtils.getFilenameExtension(fileName);
    
    
    
    
			if (!extension.equalsIgnoreCase(_extension))
    
    
    
    
			{
    
    
    
    
				destFile = new File(destFile.getParent(), fileName.concat(".")
    
    
    
    
						.concat(extension));
    
    
    
    
			}
    
    
    
    
			builder.toFile(destFile);
    
    
    
    
			return destFile;
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public void writeToStream(OutputStream stream) throws Exception {
    
    
    
    
			builder.toOutputStream(stream);
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public int getWidth() throws IOException {
    
    
    
    
			return builder.asBufferedImage().getWidth();
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public int getHeight() throws IOException {
    
    
    
    
			return builder.asBufferedImage().getHeight();
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public String getExtension() {
    
    
    
    
			return extension;
    
    
    
    
		}
    
    
    
    
	}
    
    
    
    
 
    
    
    
    
}
   
   
   
   

imgscalr，同样拥有图片压缩、裁剪等功能，使用同样非常简单。不过它好像没有输出到文件或者输出到流的功能（也许我没发现），它还支持多线程压缩？，感兴趣的可以看看  org.imgscalr.AsyncScalr  
项目地址: 
https://github.com/thebuzzmedia/imgscalr  或者  http://www.thebuzzmedia.com/software/imgscalr-java-image-scaling-library/  
官网上的例子:

   
   
   
   

    
    
    
    
BufferedImage thumbnail =
    
    
    
    
  Scalr.resize(image, Scalr.Method.SPEED, Scalr.Mode.FIT_TO_WIDTH,
    
    
    
    
               150, 100, Scalr.OP_ANTIALIAS);
   
   
   
   

具体使用:

   
   
   
   

    
    
    
    
public class ImageScalrThumbnailer extends AbstractThumbaniler{
    
    
    
    
 
    
    
    
    
	@Override
    
    
    
    
	ThumbnailResult createThumbnail(BufferedImage image, ScalrConfig config,
    
    
    
    
			String oldExtension) throws Exception {
    
    
    
    
		Integer size = config.getSize();
    
    
    
    
		if(size != null)
    
    
    
    
		{
    
    
    
    
			image = Scalr.resize(image, Method.QUALITY, size);
    
    
    
    
		}
    
    
    
    
		else
    
    
    
    
		{
    
    
    
    
			if(!config.getAspectRatio())
    
    
    
    
			{
    
    
    
    
				image = Scalr.resize(image, Method.QUALITY,
    
    
    
    
						Mode.FIT_EXACT,config.getWidth(),config.getHeight());
    
    
    
    
			}
    
    
    
    
			else
    
    
    
    
			{
    
    
    
    
				image = Scalr.resize(image, Method.QUALITY,
    
    
    
    
						config.getWidth(),config.getHeight());
    
    
    
    
			}
    
    
    
    
		}
    
    
    
    
		if (config.isRetype())
    
    
    
    
		{
    
    
    
    
			String newExtension = config.getType().name();
    
    
    
    
			if (!ImageExtensionEnum.isSameType(newExtension, oldExtension))
    
    
    
    
				oldExtension = newExtension;
    
    
    
    
		}
    
    
    
    
		return new ImgScalrThumbnailResult(oldExtension,
    
    
    
    
				config.getQuality(),image);
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	private final class ImgScalrThumbnailResult implements ThumbnailResult{
    
    
    
    
		
    
    
    
    
		private String extension ;
    
    
    
    
		
    
    
    
    
		private Float quality;
    
    
    
    
		
    
    
    
    
		private BufferedImage image;
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public File writeToFile(File destFile) throws Exception {
    
    
    
    
			String filename = destFile.getName();
    
    
    
    
			String targetExtension = MyStringUtils.getFilenameExtension(filename);
    
    
    
    
			if(!ImageExtensionEnum.isSameType(extension, targetExtension))
    
    
    
    
			{
    
    
    
    
				destFile = new File(destFile.getParent(),
    
    
    
    
						filename.concat(".").concat(extension));
    
    
    
    
			}
    
    
    
    
			ImageUtils.write(image, extension, quality, destFile);
    
    
    
    
			return destFile;
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public void writeToStream(OutputStream stream) throws Exception {
    
    
    
    
			ImageUtils.write(image, extension, quality, stream);
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public int getWidth() {
    
    
    
    
			return image.getWidth();
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public int getHeight() {
    
    
    
    
			return image.getHeight();
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		@Override
    
    
    
    
		public String getExtension(){
    
    
    
    
			return extension;
    
    
    
    
		}
    
    
    
    
 
    
    
    
    
		private ImgScalrThumbnailResult(String extension, Float quality,
    
    
    
    
				BufferedImage image) {
    
    
    
    
			this.extension = extension;
    
    
    
    
			this.quality = quality;
    
    
    
    
			this.image = image;
    
    
    
    
		}
    
    
    
    
		
    
    
    
    
	}
    
    
    
    
 
    
    
    
    
 
    
    
    
    
}
   
   
   
   

ImageUtils用来讲BufferedImage输出到文件或者流，具体如下（来源于Thumbanailator的util）:

   
   
   
   

    
    
    
    
public final class ImageUtils {
    
    
    
    
	
    
    
    
    
	public static void write(BufferedImage img , String formatName,
    
    
    
    
			Float quality,File destFile) throws IOException{
    
    
    
    
		Iterator<ImageWriter> writers =
    
    
    
    
			ImageIO.getImageWritersByFormatName(formatName);
    
    
    
    
		if (!writers.hasNext())
    
    
    
    
		{
    
    
    
    
			throw new UnsupportedFormatException(
    
    
    
    
					formatName,
    
    
    
    
					"No suitable ImageWriter found for " + formatName + "."
    
    
    
    
			);
    
    
    
    
		}
    
    
    
    
		ImageWriter writer = writers.next();
    
    
    
    
		ImageWriteParam writeParam = writer.getDefaultWriteParam();
    
    
    
    
		if (writeParam.canWriteCompressed())
    
    
    
    
		{
    
    
    
    
			writeParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    
    
    
    
			List<String> supportedFormats =
    
    
    
    
				ThumbnailatorUtils.getSupportedOutputFormatTypes(formatName);
    
    
    
    
			
    
    
    
    
			if (!supportedFormats.isEmpty())
    
    
    
    
			{
    
    
    
    
				writeParam.setCompressionType(supportedFormats.get(0));
    
    
    
    
			}
    
    
    
    
			if(quality != null)
    
    
    
    
			{
    
    
    
    
				writeParam.setCompressionQuality(quality);
    
    
    
    
			}
    
    
    
    
		}
    
    
    
    
		ImageOutputStream ios;
    
    
    
    
		FileOutputStream fos;
    
    
    
    
		fos = new FileOutputStream(destFile);
    
    
    
    
		ios = ImageIO.createImageOutputStream(fos);
    
    
    
    
		if (ios == null || fos == null)
    
    
    
    
		{
    
    
    
    
			throw new IOException("Could not open output file.");
    
    
    
    
		}
    
    
    
    
		if (
    
    
    
    
				formatName.equalsIgnoreCase("jpg")
    
    
    
    
				|| formatName.equalsIgnoreCase("jpeg")
    
    
    
    
				|| formatName.equalsIgnoreCase("bmp")
    
    
    
    
		)
    
    
    
    
		{
    
    
    
    
			int width = img.getWidth();
    
    
    
    
			int height = img.getHeight();
    
    
    
    
			BufferedImage newImage = new BufferedImage(width, height,
    
    
    
    
					BufferedImage.TYPE_INT_RGB);
    
    
    
    
			Graphics g = newImage.createGraphics();
    
    
    
    
			g.drawImage(img, 0, 0, null);
    
    
    
    
			g.dispose();
    
    
    
    
			img = newImage;
    
    
    
    
		}
    
    
    
    
		writer.setOutput(ios);
    
    
    
    
		writer.write(null, new IIOImage(img, null, null), writeParam);
    
    
    
    
		writer.dispose();
    
    
    
    
		ios.close();
    
    
    
    
		fos.close();
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	public static void write(BufferedImage img,String formatName,
    
    
    
    
			Float quality,OutputStream os) throws IOException{
    
    
    
    
		Iterator<ImageWriter> writers =
    
    
    
    
			ImageIO.getImageWritersByFormatName(formatName);
    
    
    
    
		if (!writers.hasNext())
    
    
    
    
		{
    
    
    
    
			throw new UnsupportedFormatException(
    
    
    
    
					formatName,
    
    
    
    
					"No suitable ImageWriter found for " + formatName + "."
    
    
    
    
			);
    
    
    
    
		}
    
    
    
    
		ImageWriter writer = writers.next();
    
    
    
    
		ImageWriteParam writeParam = writer.getDefaultWriteParam();
    
    
    
    
		if (writeParam.canWriteCompressed())
    
    
    
    
		{
    
    
    
    
			writeParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    
    
    
    
			List<String> supportedFormats =
    
    
    
    
				ThumbnailatorUtils.getSupportedOutputFormatTypes(formatName);
    
    
    
    
			
    
    
    
    
			if (!supportedFormats.isEmpty())
    
    
    
    
			{
    
    
    
    
				writeParam.setCompressionType(supportedFormats.get(0));
    
    
    
    
			}
    
    
    
    
			if (quality != null)
    
    
    
    
			{
    
    
    
    
				writeParam.setCompressionQuality(quality);
    
    
    
    
			}
    
    
    
    
		}
    
    
    
    
		ImageOutputStream ios = ImageIO.createImageOutputStream(os);
    
    
    
    
		if (ios == null)
    
    
    
    
		{
    
    
    
    
			throw new IOException("Could not open OutputStream.");
    
    
    
    
		}
    
    
    
    
		if (
    
    
    
    
				formatName.equalsIgnoreCase("jpg")
    
    
    
    
				|| formatName.equalsIgnoreCase("jpeg")
    
    
    
    
				|| formatName.equalsIgnoreCase("bmp")
    
    
    
    
		)
    
    
    
    
		{
    
    
    
    
			int width = img.getWidth();
    
    
    
    
			int height = img.getHeight();
    
    
    
    
			BufferedImage newImage = new BufferedImage(width, height,
    
    
    
    
					BufferedImage.TYPE_INT_RGB);
    
    
    
    
			Graphics g = newImage.createGraphics();
    
    
    
    
			g.drawImage(img, 0, 0, null);
    
    
    
    
			g.dispose();
    
    
    
    
			img = newImage;
    
    
    
    
		}
    
    
    
    
		writer.setOutput(ios);
    
    
    
    
		writer.write(null, new IIOImage(img, null, null), writeParam);
    
    
    
    
		writer.dispose();
    
    
    
    
		ios.close();
    
    
    
    
	}
    
    
    
    
 
    
    
    
    
}
   
   
   
   

MyStringUitls主要用来获取文件后缀名: 
 

   
   
   
   

    
    
    
    
public class MyStringUtils {
    
    
    
    
	
    
    
    
    
	private static final char EXTENSION_SEPARATOR = '.';
    
    
    
    
	
    
    
    
    
	private static final String FOLDER_SEPARATOR = "/";
    
    
    
    
	
    
    
    
    
	public static String getFilenameExtension(String path) {
    
    
    
    
		if (path == null) {
    
    
    
    
			return null;
    
    
    
    
		}
    
    
    
    
		int extIndex = path.lastIndexOf(EXTENSION_SEPARATOR);
    
    
    
    
		if (extIndex == -1) {
    
    
    
    
			return null;
    
    
    
    
		}
    
    
    
    
		int folderIndex = path.lastIndexOf(FOLDER_SEPARATOR);
    
    
    
    
		if (folderIndex > extIndex) {
    
    
    
    
			return null;
    
    
    
    
		}
    
    
    
    
		return path.substring(extIndex + 1);
    
    
    
    
	}
    
    
    
    
 
    
    
    
    
}
   
   
   
   

测试:
 

   
   
   
   

    
    
    
    
public class Test {
    
    
    
    
	
    
    
    
    
	public static void main(String [] args) throws Exception{
    
    
    
    
		Thumbnailer thumbnailer = ThumbnailerFactory.getThumbnailer();
    
    
    
    
		File toThumbnail = new File("q:/user.bmp");
    
    
    
    
		ScalrConfig config = new ScalrConfig(104,105, 160,160);
    
    
    
    
		config.setAspectRatio(true);
    
    
    
    
		config.setQuality(1F);
    
    
    
    
		config.setType(ImageExtensionEnum.BMP);
    
    
    
    
		List<ThumbnailResult> results = thumbnailer.
    
    
    
    
				createThumbnails(toThumbnail, config);
    
    
    
    
		if(!results.isEmpty())
    
    
    
    
		{
    
    
    
    
			File destFile = new File("q:/target22222.bmp");
    
    
    
    
			ThumbnailResult result = results.get(0);
    
    
    
    
			result.writeToFile(destFile);
    
    
    
    
		}
    
    
    
    
	}
    
    
    
    
	
    
    
    
    
	
    
    
    
    
}