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  1. #1
    atiprashant is offline Member
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    Default Doubt in assigning pixel values in MemoryImageSource

    Hello everyone....!!!

    I am having problem in understanding the following piece of code...

    int alpha = (rgb >> 24) & 0xff;

    I am not able to get what value will be assigned to alpha here..

    Please help

    Thanks in advance...:):):)

  2. #2
    Norm's Avatar
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    What does this have to do with Java Applets?
    You're in the wrong part of this forum.

  3. #3
    atiprashant is offline Member
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    Default

    It is used in MemoryImageSource part of JAVA applets.

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    Quote Originally Posted by Norm View Post
    What does this have to do with Java Applets?
    You're in the wrong part of this forum.
    Agreed. Moved to Java2D

    db

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    int alpha = (rgb >> 24) & 0xff;

    I am not able to get what value will be assigned to alpha here..
    Bitwise and Bit Shift Operators (The Java™ Tutorials > Learning the Java Language > Language Basics)

    db

  6. #6
    atiprashant is offline Member
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    Default Applet to make a MemoryimageSource

    I have a doubt in this piece of code


    int w = 100;
    int h = 100;
    int pix[] = new int[w * h];
    int index = 0;
    for (int y = 0; y < h; y++) {
    int red = (y * 255) / (h - 1);
    for (int x = 0; x < w; x++) {
    int blue = (x * 255) / (w - 1);
    pix[index++] = (255 << 24) | (red << 16) | blue;
    }
    }
    Image img = createImage(new MemoryImageSource(w, h, pix, 0, w));

    int pixels[];
    MemoryImageSource source;

    public void init() {
    int width = 50;
    int height = 50;
    int size = width * height;
    pixels = new int[size];

    int value = getBackground().getRGB();
    for (int i = 0; i < size; i++) {
    pixels[i] = value;
    }

    source = new MemoryImageSource(width, height, pixels, 0, width);
    source.setAnimated(true);
    image = createImage(source);
    }

    public void run() {
    Thread me = Thread.currentThread( );
    me.setPriority(Thread.MIN_PRIORITY);

    while (true) {
    try {
    thread.sleep(10);
    } catch( InterruptedException e ) {
    return;
    }

    // Modify the values in the pixels array at (x, y, w, h)

    // Send the new data to the interested ImageConsumers
    source.newPixels(x, y, w, h);
    }
    }

    In this code you can find a highlighted , bold line...

    Can anyone please explain me how that assignment goes. I mean how values to pixels are assigned...

    Thanks...:) :)

  7. #7
    Norm's Avatar
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    Try writing a simple one line program that prints out the results of different shifts and ORs.
    Use Integer.toHexString() to display the results.
    Keep trying different combinations until you get what you want.

  8. #8
    DarrylBurke's Avatar
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    atiprashant , please use one thread per question. I've merged your two threads which are about the same problem.

    db

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