Re: have to use different image types, depending on the OS. how?

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 20 Jun 2007 16:40:19 -0700

Message-ID:

<FViei.35366$2K1.34630@newsfe18.lga>

linuxadmin@yandex.ru wrote:

hello!

i load JPEG images into BufferedImage objects and draw them using
Graphics2D.drawImage(...)

to be able to use LookupOp (for gamma and brightness adjustments) i
have to convert them to one of the following image types:
TYPE_INT_RGB or TYPE_INT_BGR.
the JPEG-native type TYPE_INT_3BGR doesn't work.

[ note: the conversion is done by creating an empty BufferedImage with
same size but different image type, and drawing the loaded image into
the newly created image: ]

    BufferedImage img = ImageIO.read(new File(fileName));

    BufferedImage temp;
    temp = new BufferedImage(img.getWidth(), img.getHeight(),
        BufferedImage.TYPE_INT_RGB // <-problem
    );

    temp.getGraphics().drawImage(img, 0, 0, null);
    img = temp;

now the problem:
the images are drawn correctly, when using
TYPE_INT_BGR under linux but: TYPE_INT_RGB under windows.
so, when the 'wrong' type is used, the colors look ugly.

i tried to get to know the system-native image type by letting
GraphicConfiguration create a BufferedImage:

    GraphicsEnvironment ge = GraphicsEnvironment
            .getLocalGraphicsEnvironment();
    GraphicsDevice gd = ge.getDefaultScreenDevice();
    GraphicsConfiguration gc = gd.getDefaultConfiguration();
    BufferedImage bestImage = gc.createCompatibleImage(1, 1);

but: on both systems bestImage.getType() equals TYPE_INT_RGB, so under
linux the colors are wrong.

i think that it is wrong to assume, that the linux platform always
implies TYPE_INT_BGR and the windows platform always implies
TYPE_INT_RGB.

so how can i get the real system-native image type?

thanks in advice!

Try the method below to convert your image to the type you want it to
be. This method converts to a compatible type but you can make it any
type you want.

     // method to convert an image read from a file to a compatible image
     BufferedImage convertImage(BufferedImage image) {
         GraphicsEnvironment ge =
          GraphicsEnvironment.getLocalGraphicsEnvironment();
         GraphicsDevice[] devices = ge.getScreenDevices();
         GraphicsConfiguration gc =
          devices[Math.min(devices.length-1,0)].getDefaultConfiguration();

         BufferedImage compatible gc.createCompatibleImage(image.getWidth(),
          image.getHeight());

         if (compatible.getType() == image.getType())
             return image;

         ColorConvertOp op = new ColorConvertOp(
          image.getColorModel().getColorSpace(),
          compatible.getColorModel().getColorSpace(), null);
         op.filter(image, compatible);

         return compatible;
     }

--

Knute Johnson
email s/nospam/knute/