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  BufferedImage and TYPE_BYTE_GRAY  (Read 6362 times)
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Offline PeterB

Junior Devvie


Exp: 15 years



« Posted 2005-11-16 00:48:04 »

Folks,
I'm loading an 8-bit grayscale image (RAW) into a one dimensional array representing pixels.
Knowing the width and height of the image I'm using *BufferedImage* to create an *Image* object and then paint this onto the screen.
(code below)

The problem is that the loaded image (being 8bit) contains 255 colors yet the displayed image has only 19 colors:

What it should look like:


How it is displayed:


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Image image;

   // snippet
        int width = 513;
        int height = 513;
        byte[] b = null;
        int[] pixels = new int [(width*height)];
        b = generatePixels (width, height);
       
        for (int i=0; i < b.length; i++)
        {
            pixels[i] = b[i] & 0xFF;
        }

        BufferedImage recoverImg = new BufferedImage (width,height,BufferedImage.TYPE_BYTE_GRAY);
        myImg.setRGB (0,0,width,height,pixels,0,width);
        image = myImg.getScaledInstance (width, height, Image.SCALE_SMOOTH);
       
        Frame frame = new Frame ("Test");
        frame.add (this);
        frame.setSize (600, 600);
        frame.setVisible (true);
        this.repaint ();


I don't have a problem with the RAW loader - outputting the values of the array shows all colours from 0 to 255 are present. It's the displaying that seems to be the issue. Any ideas?

Offline trembovetski

Senior Devvie




If only I knew what I'm talking about!


« Reply #1 - Posted 2005-11-16 21:14:45 »

Quote
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image = myImg.getScaledInstance (width, height, Image.SCALE_SMOOTH);


I think this is your problem. Is there a reason you need to use getScaledInstance?
You don't change the size of the image.

Thanks,
  Dmitri
Java2D Team
Offline oNyx

JGO Coder


Medals: 2


pixels! :x


« Reply #2 - Posted 2005-11-16 21:27:36 »

myImg.setRGB (0,0,width,height,pixels,0,width);

There is the problem. See api doc.

"Sets an array of integer pixels in the default RGB color model (TYPE_INT_ARGB) and default sRGB color space, into a portion of the image data. Color conversion takes place if the default model does not match the image ColorModel."

That explains why the luminance is only a third of what it should be.

You could either do some bit op voodoo... or you could try MemoryImageSource... or WritableRaster...

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Offline trembovetski

Senior Devvie




If only I knew what I'm talking about!


« Reply #3 - Posted 2005-11-17 22:50:54 »

I think oNyx is correct. You need to set the pixels to the raster to avoid color conversion:
instead of Img.setRGB use
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Img.getRaster().setPixels(0, 0, width, height, pixels);


Thanks,
Dmitri
Offline PeterB

Junior Devvie


Exp: 15 years



« Reply #4 - Posted 2005-11-19 19:09:23 »

Thanks for the assistance guys! Using .getRaster().setPixels (..) seems to have fixed the problem.

Pete


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