pixel data array to BufferedImage

[Clawsy]

Hi, I have a pixel array grabbed with PixelGrabber. I done some computation with it and now I need make a BufferedImage from it. The problem is I can't make it very fast, just slow. I made an Image type object from it then I converted it to a BufferedImages but it's so slow...... To get you mode ideas of solving this, I tell you that I need to send the image over network as PNG compressed... so that's why I need a BufferedImage. I need very fast conversion/image construction...

Thanks.

[JamesCherrill]

I used the following standard solution:

ims = new MemoryImageSource(width,height, pixels, 0, width);

(where the width/height vars define the image size and pixels is a simple int array of PixelGrabber-type data

then:

Image im = Toolkit.getDefaultToolkit().createImage(ims);

It seemed to me that this was fast enough to be be negligeable compared to moving the pixel aray over the network etc.

[Clawsy]

Yes but I need a BufferedImage to do that, not Image. I can't send Image object over a dataoutputstream... or I don't know how :|

[Clawsy]

This is the code I use. Working but very slow. It is there also a version using DataBufferInt but it's also slow.

finalimg = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
               
                Image piximg =  Toolkit.getDefaultToolkit().createImage(new MemoryImageSource(w, h, pixels2,0,w));
                finalimg.getGraphics().drawImage(piximg, 0, 0, null);

[JamesCherrill]

createImage is defined as returning Image (abstract) but actually returns a BufferedImage, so you can just cast it.
However, rather than extracting pixels, prcessing them and converting back to Image, why not work directly with the Imaage's databuffer array and save both conversions:

image = robot.createScreenCapture(new Rectangle(width, height));
Raster ras = ((BufferedImage) image).getData();
DataBufferInt db = (DataBufferInt) ras.getDataBuffer();
int[] data = db.getData();

now whatever you change in data will change the image directly.

[Clawsy]

Is this at least as fast as pixel grabber? I'll code it now...

[JamesCherrill]

I found it about twice as fast, plus there's zero overhead converting back to image. Good Luck!

[Clawsy]

//same with pixel and pixel2 - similay speed with pixel grabber
            Raster ras = ((BufferedImage) img).getData();
            DataBufferInt db = (DataBufferInt) ras.getDataBuffer();
            pixels2 = db.getData();

for (int x = 0; x < w; x++) {
	for (int y = 0; y < h; y++) {
		if (pixels2[x + y * w] != pixels[x + y * w])
                {
                    pixels[x + y * w] = pixels2[x + y * w];
   
                }
                else pixels2[x + y * w] = 0;//if the same make it 0


//this take as long time as a full image - and it's still abou 120K... so maybe what I chaneg in data does not change the image directly?
 sendImageToStream(img, os_img);

[...]

public void sendImageToStream(BufferedImage img, DataOutputStream dos) throws IOException{
//i send the image as byte array and not directly write the image to stream because I need the length of the image
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
     ImageIO.write(img, "png", baos);


            
            byte[] byteArray = baos.toByteArray();
            baos.close();
            int len = byteArray.length;





            try {
                 dos.writeInt(1);
                 dos.writeInt(len);//length
                 dos.write(byteArray, 0, len);

                 dos.flush();
               
            } catch(Exception e){
                 e.printStackTrace();
            }

 }

So the pixels do not modify... need to reconstruct the image? (what I needed... pixels to BufferedImage).
Thanks.

[JamesCherrill]

Is line 11 the right way round (don't you want to change pixels2)?

[Clawsy]

//pixel2 = current image. pixel would be the previous image data
for (int x = 0; x < pixels2.length; x++) {
		if (pixels2[x] != pixels[x])                
                        pixels[x] = pixels2[x]; //save the previous image data as the current one                         
                else pixels2[x] = 0;//set current unmodified pixels to 0	
	
}

Maybe I'm missing simething?... or the data doesn't get changed directly?

[Clawsy]

I thinks the data does not change directly the image because I used this:

finalimg = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
               
                Image piximg =  Toolkit.getDefaultToolkit().createImage(new MemoryImageSource(w, h, pixels2,0,w));
                finalimg.getGraphics().drawImage(piximg, 0, 0, null);
                sendImageToStream(finalimg, os_img);

and it transmited the data, low PNG sizes 6k, 10k, for small changes... so "pixels2" data is OK, the problem is the conversion to the BufferedImag which is very slow.

[JamesCherrill]

maybe need to do a setData to re-write the raster to the image?

[Clawsy]

yes, we need, if we can. Also there is a WritableRaster parameter when you construct a buffered image... but it might take some time too...

[Clawsy]

James, I found out! We shouldn't have used:

Raster ras = ((BufferedImage) img).getData();

I used:

WritableRaster wras = ((BufferedImage) img).getRaster();

and it worked... directly modified the buffered image!
I'll mark this as solved. Thanks. I still have delay because of the compression... but I will post it in the 'big' thread.
Thanks!

[JamesCherrill]

Brilliant! Thanks for sharing the answer.
J