java如何在上传后以thumnail格式存储jpeg、gif和图像

Question

我通过JavaAPI上传图像、gif文件，之后我想以缩略图格式保存文件

Answer 1

通常没有“缩略图格式”，而是使用图像库将上传的图像调整为特定的小尺寸，压缩它们，并与原始图像一起保存

我不熟悉Java中的图像格式库，但肯定会有其他人回答这个问题

Answer 2

遵循以下步骤：

1. 从上传的项目中获取InputStream
2. 使用ImageIO加载并重新缩放图像（谷歌搜索“java缩放图像”）
3. 将新缩放的图像另存为imagename_thumb.extension

Answer 3

你可以看看this。这是一个德语组，但提供的代码是英语：-）

Answer 4

从http://viralpatel.net/blogs/2009/05/20-useful-java-code-snippets-for-java-developers.html：

private void createThumbnail(String filename, int thumbWidth, int thumbHeight, int quality, String outFilename)
02          throws InterruptedException, FileNotFoundException, IOException
03      {
04          // load image from filename
05          Image image = Toolkit.getDefaultToolkit().getImage(filename);
06          MediaTracker mediaTracker = new MediaTracker(new Container());
07          mediaTracker.addImage(image, 0);
08          mediaTracker.waitForID(0);
09          // use this to test for errors at this point: System.out.println(mediaTracker.isErrorAny());
10   
11          // determine thumbnail size from WIDTH and HEIGHT
12          double thumbRatio = (double)thumbWidth / (double)thumbHeight;
13          int imageWidth = image.getWidth(null);
14          int imageHeight = image.getHeight(null);
15          double imageRatio = (double)imageWidth / (double)imageHeight;
16          if (thumbRatio < imageRatio) {
17              thumbHeight = (int)(thumbWidth / imageRatio);
18          } else {
19              thumbWidth = (int)(thumbHeight * imageRatio);
20          }
21   
22          // draw original image to thumbnail image object and
23          // scale it to the new size on-the-fly
24          BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB);
25          Graphics2D graphics2D = thumbImage.createGraphics();
26          graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
27          graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);
28   
29          // save thumbnail image to outFilename
30          BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outFilename));
31          JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
32          JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(thumbImage);
33          quality = Math.max(0, Math.min(quality, 100));
34          param.setQuality((float)quality / 100.0f, false);
35          encoder.setJPEGEncodeParam(param);
36          encoder.encode(thumbImage);
37          out.close();
38      }

您需要弄清楚所有类都来自何处，但看起来它们并没有使用任何未与JDK捆绑在一起的东西（尽管我可能错了）