使用BufferedImage的DataBuffer来设置像素

Question

I am trying to use the underlying DataBufferByte of a BufferedImage of type TYPE_3BYTE_BGR to set pixel values as quick as possible.

Perhaps I am not understanding, but when I do the following...

byte[] imgBytes = ((DataBufferByte) img.getData().getDataBuffer()).getData();

... it seems as though I am getting a copy of the byte[] and not a reference. For example, if I run...

System.out.println(System.identityHashCode(imgBytes));
System.out.println(System.identityHashCode((DataBufferByte) img.getData().getDataBuffer()).getData());

... I get two clearly different object hashes. If I'm not mistaken, this indicates that I am not getting a reference to the underlying byte[] but rather a copy. If this is the case, how am I supposed to edit the DataBufferByte directly???

Or perhaps I am just setting the pixels wrong... When I set pixels in the imgBytes it doesn't seem to do anything to the BufferedImage. Once I get the byte[], I set each pixel value like so:

imgBytes[intOffset] = byteBlue;
imgBytes[intOffset+1] = byteGreen;
imgBytes[intOffset+2] = byteRed;

To me, this all seems fine. I can read pixels just fine this way so it seems I should be able to write them the same way!

Answer 1

I had the same problem. You may not use getData() but use getRaster() which gives you an array you can use to write to.

Answer 2

I once played around with pixel manipulations for Images in Java. Instead of directly answering your question I will offer an alternative solution to your problem. You can do the following to create an array of pixels to manipulate:

final int width = 800;
final int height = 600;
final int[] pixels = new int[width * height]; // 0xAARRGGBB
MemoryImageSource source = new MemoryImageSource(width, height, pixels, 0, width);
source.setAnimated(true);
source.setFullBufferUpdates(true);
Image image = Toolkit.getDefaultToolkit().createImage(source);
image.setAccelerationPriority(1f);

Then to draw the image, you can simply call the drawImage method from the Graphics class.

There are a few other ways to achieve what you are looking for, but this method was the simplest to me.

Answer 3

Here is how it's implemented in JDK7. You may have an error somewhere else if the stuff doesn't work for you.

public byte[] getData() {
    theTrackable.setUntrackable();
    return data;
}