在Java中创建图像的缩略图

Posted 2021-02-23

Create Thumbnail of an image in Java

private void createThumbnail(String filename, int thumbWidth, int thumbHeight, int quality, String outFilename)
        throws InterruptedException, FileNotFoundException, IOException
    {
        // load image from filename
        Image image = Toolkit.getDefaultToolkit().getImage(filename);
        MediaTracker mediaTracker = new MediaTracker(new Container());
        mediaTracker.addImage(image, 0);
        mediaTracker.waitForID(0);
        // use this to test for errors at this point: System.out.println(mediaTracker.isErrorAny());
 
        // determine thumbnail size from WIDTH and HEIGHT
        double thumbRatio = (double)thumbWidth / (double)thumbHeight;
        int imageWidth = image.getWidth(null);
        int imageHeight = image.getHeight(null);
        double imageRatio = (double)imageWidth / (double)imageHeight;
        if (thumbRatio < imageRatio) {
            thumbHeight = (int)(thumbWidth / imageRatio);
        } else {
            thumbWidth = (int)(thumbHeight * imageRatio);
        }
 
        // draw original image to thumbnail image object and
        // scale it to the new size on-the-fly
        BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics2D = thumbImage.createGraphics();
        graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);
 
        // save thumbnail image to outFilename
        BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outFilename));
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(thumbImage);
        quality = Math.max(0, Math.min(quality, 100));
        param.setQuality((float)quality / 100.0f, false);
        encoder.setJPEGEncodeParam(param);
        encoder.encode(thumbImage);
        out.close();
    }