ImageIO.createImageInputStream保持返回null

Question

嘿所有,每当我尝试ImageInputStream使用ImageIO.createImageInputStream它来获取一个对象时,只返回null没有异常,警告或错误.我已经尝试将不同的数据类型传递给函数,一个简单的File,一个InputStream,但两者都返回null.文档说如果没有ImageInputStreamSpi找到合适的,那么该函数将返回null,但该文件是一个标准的JPEG标准,并且Java肯定会带有一个开箱即用的格式的服务提供商？谢谢你的时间.

/**
 * Reads in an image from a file and returns the image in a
 * {@code BufferedImage} object.
 *
 * @param source the file to create the {@code BufferedImage}
 * from.
 * @return the {@code BufferedImage} object representing the image
 * in {@code source}.
 */
private BufferedImage readImage( File source ) {
    // There is only one image in this file
    final int imageIndex = 0;
    BufferedImage image = null;

    try {
        // Get the ImageReader object for this filetype
        Iterator readers =
            ImageIO.getImageReaders( source );
        ImageReader reader = (ImageReader) readers.next();

        // Create an ImageInputStream object from the source image file
        ImageInputStream iis = ImageIO.createImageInputStream( source );
        // Raises IllegalArgumentException, because iis is null
        reader.setInput( iis, true );

        // Read the image file
        image = reader.read( imageIndex );
    } catch ( Exception exception ) {
        exception.printStackTrace();
        System.exit( -1 );
    }

    return image;
}

Answer 1

你为什么要做这一切？你可以简单地这样做：

image = ImageIO.read(source);

不Iterators，ImageInputStreams……什么都没有！

编辑：既然您坚持认为，您的代码不起作用，因为您发送的是FiletoImageIO.getImageReaders()而不是ImageInputStream。所以你的代码应该看起来像这样：

ImageInputStream iis = ImageIO.createImageInputStream(source);
Iterator readers = ImageIO.getImageReaders(iis);
ImageReader reader = (ImageReader) readers.next();

reader.setInput(iis, false);
image = reader.read(imageIndex);