修复Java中动画gif的帧频

Question

我正在制作一个Java应用程序，它显示文件夹中的某些GIF文件。我目前正在使用代码

  final JLabel imageLabel = new JLabel();
  imageLabel.setIcon(new ImageIcon(fileName));
  contentPane.add(imageLabel, java.awt.BorderLayout.CENTER);

可以正常工作，只是我的许多.GIF文件的帧速率配置不正确，前提是浏览器会自动修复此问题，从而使它们以无限的速度显示（frameDelay =
0）。Java默认情况下不执行此操作。如何覆盖frameDelay = 0的Java动画gif必须使用的frameDelay？

Answer 1

我已经找到了，并且非常适合我尝试过的一个gif。

我不知道他到底在做什么，但是乍一看， 如果第一帧的延迟为0，它将覆盖所有帧的延迟，即为10。然后他“写入”内存中的新GIF文件并将其加载到图片。

[编辑]我将它擦亮了一点，并消除了这些错误。

• 没有专有的API
• 不只是检查第一帧以确定它是否被窃听，

• 仅将延迟替换为零的帧。

  public static Image readImgFromFile(String filename, Component parent) {
  File file = new File(filename);
  if (!file.exists()) {
  return null;
  }
  
  

  // Fix for bug when delay is 0
  try {
      // Load anything but GIF the normal way
      if (!filename.substring(filename.length() - 4).equalsIgnoreCase(".gif")) {
          return ImageIO.read(file);
      }
  
      // Get GIF reader
      ImageReader reader = ImageIO.getImageReadersByFormatName("gif").next();
      // Give it the stream to decode from
      reader.setInput(ImageIO.createImageInputStream(file));
  
      int numImages = reader.getNumImages(true);
  
      // Get 'metaFormatName'. Need first frame for that.
      IIOMetadata imageMetaData = reader.getImageMetadata(0);
      String metaFormatName = imageMetaData.getNativeMetadataFormatName();
  
      // Find out if GIF is bugged
      boolean foundBug = false;
      for (int i = 0; i < numImages && !foundBug; i++) {
          // Get metadata
          IIOMetadataNode root = (IIOMetadataNode)reader.getImageMetadata(i).getAsTree(metaFormatName);
  
          // Find GraphicControlExtension node
          int nNodes = root.getLength();
          for (int j = 0; j < nNodes; j++) {
              Node node = root.item(j);
              if (node.getNodeName().equalsIgnoreCase("GraphicControlExtension")) {
                  // Get delay value
                  String delay = ((IIOMetadataNode)node).getAttribute("delayTime");
  
                  // Check if delay is bugged
                  if (Integer.parseInt(delay) == 0) {
                      foundBug = true;
                  }
  
                  break;
              }
          }
      }
  
      // Load non-bugged GIF the normal way
      Image image;
      if (!foundBug) {
          image = Toolkit.getDefaultToolkit().createImage(filename);
      } else {
          // Prepare streams for image encoding
          ByteArrayOutputStream baoStream = new ByteArrayOutputStream();
          try (ImageOutputStream ios = ImageIO.createImageOutputStream(baoStream)) {
              // Get GIF writer that's compatible with reader
              ImageWriter writer = ImageIO.getImageWriter(reader);
              // Give it the stream to encode to
              writer.setOutput(ios);
  
              writer.prepareWriteSequence(null);
  
              for (int i = 0; i < numImages; i++) {
                  // Get input image
                  BufferedImage frameIn = reader.read(i);
  
                  // Get input metadata
                  IIOMetadataNode root = (IIOMetadataNode)reader.getImageMetadata(i).getAsTree(metaFormatName);
  
                  // Find GraphicControlExtension node
                  int nNodes = root.getLength();
                  for (int j = 0; j < nNodes; j++) {
                      Node node = root.item(j);
                      if (node.getNodeName().equalsIgnoreCase("GraphicControlExtension")) {
                          // Get delay value
                          String delay = ((IIOMetadataNode)node).getAttribute("delayTime");
  
                          // Check if delay is bugged
                          if (Integer.parseInt(delay) == 0) {
                              // Overwrite with a valid delay value
                              ((IIOMetadataNode)node).setAttribute("delayTime", "10");
                          }
  
                          break;
                      }
                  }
  
                  // Create output metadata
                  IIOMetadata metadata = writer.getDefaultImageMetadata(new ImageTypeSpecifier(frameIn), null);
                  // Copy metadata to output metadata
                  metadata.setFromTree(metadata.getNativeMetadataFormatName(), root);
  
                  // Create output image
                  IIOImage frameOut = new IIOImage(frameIn, null, metadata);
  
                  // Encode output image
                  writer.writeToSequence(frameOut, writer.getDefaultWriteParam());
              }
  
              writer.endWriteSequence();
          }
  
          // Create image using encoded data
          image = Toolkit.getDefaultToolkit().createImage(baoStream.toByteArray());
      }
  
      // Trigger lazy loading of image
      MediaTracker mt = new MediaTracker(parent);
      mt.addImage(image, 0);
      try {
          mt.waitForAll();
      }
      catch (InterruptedException e) {
          image = null;
      }
      return image;
  }
  catch (IOException e) {
      e.printStackTrace();
      return null;
  }
  

  }