How to draw a bitmap with transparency

How to draw a bitmap with a given 开发者_Go百科color set as transparent?

For example I want all white pixels to be transparent.

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You need to set the Alpha value for the paint you're passing to the Bitmap.

http://developer.android.com/reference/android/graphics/Paint.html#setAlpha%28int%29

Values vary from 0-255

EDIT:

Paint p = new Paint();
//Set Blue Color
p.setColor(Color.WHITE);
//Set transparency roughly at 50%
p.setAlpha(125);

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you need to check every pixel of image and change its color. you will get your answer in this Post

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Another approach is drawing in trasparent color on your canvas (drawing holes). The bitmapu needs alpha channel.

    //Set transparent paint - you need all of these three
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setXfermode(new PorterDuffXfermode(Mode.SRC_OUT));
    paint.setColor(Color.TRANSPARENT);

    // Do you wanna soften?
    // Set paint transparency:
    // 0 = transparent ink, no visible effect
    // 255 = full ink, hole in the bitmap
    p.setAlpha(192);

    // Do you want some blur?
    // Set blur radius in pixel
    paint.setMaskFilter(new BlurMaskFilter(10, Blur.NORMAL));