java - ImageIO 中的异常 "java.lang.IllegalArgumentException: image == null!"

Question

我正在尝试从字节数组写入 png 文件。

我的应用程序抛出以下异常“java.lang.IllegalArgumentException:image == null!”在ImageIO中

我使用随机字节数组测试了我的解决方案，如下面的代码片段所示，但仍然抛出异常。

你能帮我确定为什么会抛出它吗？

    import java.io.ByteArrayOutputStream;
    import java.io.File;
    import java.io.IOException;
    import java.util.Random;
    import javax.imageio.ImageIO;
    public class Main {

        public static void main(String[] args) throws IOException {
            String fn = new String("C:\\Users\\frogwine\\Desktop\\P1.png");

            byte [] data = new byte[256];

            Random r = new Random();
            r.nextBytes(data);
            ByteArrayInputStream bis = new ByteArrayInputStream(data);
            ByteArrayInputStream input_stream= new ByteArrayInputStream(data);
            BufferedImage final_buffered_image = ImageIO.read(input_stream);
            ImageIO.write(final_buffered_image , "png", new File(fn) );
        }


    }

堆栈跟踪:

    "C:\Program Files\Java\jdk-13.0.1\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3\lib\idea_rt.jar=57315:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\frogwine\Documents\deneme\out\production\deneme com.berk.Main
    Exception in thread "main" java.lang.IllegalArgumentException: image == null!
        at java.desktop/javax.imageio.ImageTypeSpecifier.createFromRenderedImage(ImageTypeSpecifier.java:925)
        at java.desktop/javax.imageio.ImageIO.getWriter(ImageIO.java:1608)
        at java.desktop/javax.imageio.ImageIO.write(ImageIO.java:1540)
        at com.berk.Main.main(Main.java:23)

    Process finished with exit code 1

Answer 1

这并不奇怪。来自ImageIO.read文档:

If no registered ImageReader claims to be able to read the resulting stream, null is returned.

将随机字节写入数组不会创建任何格式的有效图像数据，因为图像格式具有至少由 header 组成的标准结构。因此，ImageIO.read 返回 null。