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Re: 4-byte greyscale imag

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  Re: 4-byte greyscale imag "Daniele Futtorovic" <daniele.futtorovic@THRWHITE.remove-dii-this> - 2011-04-27 15:45 +0000
    Re: 4-byte greyscale imag Paul.Lee.1971@gmail.com.remove-dii-this - 2011-04-27 15:45 +0000

#3602 — Re: 4-byte greyscale imag

  To: comp.lang.java.gui
On 2008-06-03 16:02 +0100, Paul.Lee.1971@gmail.com allegedly wrote:
> Hi everyone,
> Hopefully someone can help me, this is really "bugging me" !
> 
> I have a RGB image, and I'm trying to get the Y Luminance component to
> display and manipulate. I think I've done something that goes someway
> to solving this:
> 
> BufferedImage greyImage=new
> BufferedImage(img.getWidth(),img.getHeight(),BufferedImage.TYPE_BYTE_GRAY);
>       greyImage.getGraphics().drawImage(img,0,0,null);
> 
> The problem now is that the image is an 8 bit grayscale image. What
> I'd like to be able to do is draw colours transparently on top of the
> grey image; in effect "colouring in" the image but leaving the details
> of the background untouched. For that I think I'd need RGB and alpha
> values; how can I covert the 8 bit grayscale to 32 bit/1 int
> grayscale?

Make the three lower bytes of your int the same value as your byte (8
bit int). The topmost byte defines alpha (0x0->transparent; 0xff->opaque).


-- 
DF.
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in the FROM address from "invalid" to "net"

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#3603

  To: comp.lang.java.gui
Great, thanks! I think I realised after about 2 seconds after I posted
that how to convert 8-bit grey to 24-bit color (albeit in grey :)

	BufferedImage greycolorimage = new
BufferedImage(greyimage.getWidth(),greyimage.getHeight

(),BufferedImage.TYPE_4BYTE_ABGR);  // greyimage is the original,
TYPE_BYTE_GRAY image
	greycolorimage.getGraphics().drawImage(greycolorimage,0,0,null);

Interestingly, I can't seem to write this out using:
	File output = new File("image.bmp");
	ImageIO.write(greycolorimage, "bmp", output);

If I display the image in a JFrame, it looks fine, but I wanted to
inspect the size of it to make sure that it
was 4-byte. How frustrating!

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