修复Java中动画gif的帧频

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 0try {    // 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 depre 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 enpre 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);     // Enpre output image     writer.writeToSequence(frameOut, writer.getDefaultWriteParam()); } writer.endWriteSequence();        }        // Create image using enpred 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;}

  }