java.nio.BufferUnderflowException [Bug + Fix]

Ali_RS · September 11, 2022, 11:43am

Hi

I am trying to create an image and save it in a cross-platform way with JmeSystem.writeImageFile() but I am getting this exception:

SEVERE: Uncaught exception thrown in Thread[jME3 Main,5,main]
java.nio.BufferUnderflowException
	at java.base/java.nio.IntBuffer.get(IntBuffer.java:798)
	at java.base/java.nio.IntBuffer.get(IntBuffer.java:826)
	at com.jme3.util.Screenshots.convertScreenShot2(Screenshots.java:56)
	at com.jme3.system.JmeDesktopSystem.writeImageFile(JmeDesktopSystem.java:94)
	at com.jme3.system.JmeSystem.writeImageFile(JmeSystem.java:143)
	at image.TestImageWrite.simpleInitApp(TestImageWrite.java:42)
	at com.jme3.app.SimpleApplication.initialize(SimpleApplication.java:240)
	at com.jme3.system.lwjgl.LwjglWindow.initInThread(LwjglWindow.java:548)
	at com.jme3.system.lwjgl.LwjglWindow.run(LwjglWindow.java:662)
	at java.base/java.lang.Thread.run(Thread.java:833)

My code:

public class TestImageWrite extends SimpleApplication {

    public static void main(String[] args) {
        new TestImageWrite().start();
    }

    @Override
    public void simpleInitApp() {

        ByteBuffer data = BufferUtils.createByteBuffer(512 * 512 * 4);
        Image image = new Image(Image.Format.RGBA8, 512, 512, data);
        Texture texture = new Texture2D(image);
        ImageRaster raster = ImageRaster.create(texture.getImage());
        for (int h = 0; h < texture.getImage().getHeight(); h++) {
            for (int w = 0; w < texture.getImage().getWidth(); w++) {
                raster.setPixel(w, h, ColorRGBA.Blue);
            }
        }

        File f = new File("/home/ali/Desktop/test.png");
        try {
            JmeSystem.writeImageFile(new FileOutputStream(f), "png", data, texture.getImage().getWidth(), texture.getImage().getHeight());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

If I remove these lines error goes away:

        ImageRaster raster = ImageRaster.create(texture.getImage());
        for (int h = 0; h < texture.getImage().getHeight(); h++) {
            for (int w = 0; w < texture.getImage().getWidth(); w++) {
                raster.setPixel(w, h, ColorRGBA.Blue);
            }
        }

As mentioned in Javadoc the image is in RGBA8 format:

github.com

jMonkeyEngine/jmonkeyengine/blob/f0918a4caf4eb592add2221243afb4dfcf13ca28/jme3-core/src/main/java/com/jme3/system/JmeSystem.java#L137


      
          

          /**

           * Compresses a raw image into a stream.

           * 

           * The encoding is performed via system libraries. On desktop, the encoding

           * is performed via ImageIO, whereas on Android, is done via the 

           * Bitmap class.

           * 

           * @param outStream The stream where to write the image data.

           * @param format The format to use, either "png" or "jpg".

           * @param imageData The image data in {@link com.jme3.texture.Image.Format#RGBA8} format.

           * @param width The width of the image.

           * @param height The height of the image.

           * @throws IOException If outStream throws an exception while writing.

           */

          public static void writeImageFile(OutputStream outStream, String format, ByteBuffer imageData, int width, int height) throws IOException {

              checkDelegate();

              systemDelegate.writeImageFile(outStream, format, imageData, width, height);

          }

          

          public static AssetManager newAssetManager(URL configFile) {

Any help?

Thanks in advance

Edit:
Related post/issue:

github.com/jMonkeyEngine/jmonkeyengine

JmeSystemDelegate#writeImageFile format conversion

opened 08:29PM - 16 Feb 20 UTC

closed 08:09AM - 09 Feb 23 UTC

MeFisto94

bug question

So I was quite surprised to see that writeImageFile doesn't just do that: Writin…g a byte[] as image to disk but instead attempts some conversation through `Screenshots#convertScreenShot2`. In fact, this file assumes that the format is "BGRX8"/INT_BGR and not BGR8 as I was passing, but there is no comment and also no way to override the behavior. Even worse: `convertScreenShot2` is a no-op, just copying the data from a buffer into an AWT object. Actual issue: ``` java.nio.BufferUnderflowException at java.nio.IntBuffer.get(IntBuffer.java:688) at java.nio.IntBuffer.get(IntBuffer.java:715) at com.jme3.util.Screenshots.convertScreenShot2(Screenshots.java:50) at com.jme3.system.JmeDesktopSystem.writeImageFile(JmeDesktopSystem.java:94) at com.jme3.system.JmeSystem.writeImageFile(JmeSystem.java:134) ``` This happens because I pass a ByteBuffer in BGR8 format. They get converted into an IntBuffer, i.e. 4 components, where the last one is _disregarded_ i.e. useless (see BufferedImage#TYPE_INT_BGR). This means, my byte buffer misses 1 byte per pixel information, even though this byte is thrown away. I think: - Documentation should clearly state that the bytebuffer is assumed to be in TYPE_INT_BGR (or only accept IntBuffers for that matter, then it's clear that you can't pass TYPE_3BYTE_BGR) - We should make writeImageFile independant of the type, you just pass it, so that screenshots could run their conversion before calling writeImageFile - Screenshots could read the FrameBuffer like I do: using BGR8. That way we could get rid of all the magic. Even more: Reading the written png file definitely happens in TYPE_3BYTE_BGR format, so we require the user to write the files in a differrent format than they are read in. In my usecase I can get around the issue by calling AWT APIs directly, since I don't need cross platform support, alternatively one could construct a larger buffer and interleave 0x00s

Ali_RS · September 11, 2022, 11:53am

“ScreenshotAppState” also uses JmeSystem.writeImageFile() but the difference is that ScreenshotAppState does not use ImageRaster.

Ali_RS · September 11, 2022, 6:54pm

Submitted a fix: