在画布上创一个黑色空间的Andr​​oid掩码位图 [英] Android Mask bitmap on canvas gen a black space

问题描述

我有一个半掩码位图是红色，那些是透明的这样的
https://www.dropbox.com/s/931ixef6myzusi0/s_2.png

I have a mask bitmap with a half is red color and ones is transparent like this https://www.dropbox.com/s/931ixef6myzusi0/s_2.png

我想用掩码位图绘制在画布上只在红色区域可见内容，code是这样的：

I want to use mask bitmap to draw content on canvas only visible in red area, code like this:

涂料粉刷=新的油漆（）;

Paint paint = new Paint();

公共无效画（油画画布）{
//这里画的内容
  ...

public void draw(Canvas canvas) { // draw content here ...

//和掩码位图在这里
  paint.setXfermode（新PorterDuffXfermode（android.graphics.PorterDuff.Mode.DST_IN））;
  canvas.drawBitmap（maskBitmap，0，0，油漆）;

//and mask bitmap here paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.DST_IN)); canvas.drawBitmap(maskBitmap, 0, 0, paint);

}

结果我的期待（内容仅在红色区域可见，但透明区域变成黑色是课题！）

The result as my expecting (content only visible in red area, BUT THE TRANSPARENT AREA BECOME BLACK IS PROBLEM!)

这个形象的结果： https://www.dropbox.com/s/ mqj48992wllfkiq / S_2％20copy.png
谁能帮助我？

this image result :https://www.dropbox.com/s/mqj48992wllfkiq/s_2%20copy.png Anyone help me???

推荐答案

下面是解决方案，它帮助我实现屏蔽

Here is solution which helped me to implement masking

public void draw(Canvas canvas) {
        Bitmap original = BitmapFactory.decodeResource(getContext().getResources(),R.drawable.original_image);
        Bitmap mask = Bitmap.createBitmap(getContext().getResources(),R.drawable.mask_image);

        //You can change original image here and draw anything you want to be masked on it.

        Bitmap result = Bitmap.createBitmap(mask.getWidth(), mask.getHeight(), Config.ARGB_8888);
        Canvas tempCanvas = new Canvas(result);
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
        tempCanvas.drawBitmap(original, 0, 0, null);
        tempCanvas.drawBitmap(mask, 0, 0, paint);
        paint.setXfermode(null);

        //Draw result after performing masking
        canvas.drawBitmap(result, 0, 0, new Paint());
}

面膜应与trasparency白色图像。结果
它的工作是这样的：结果
+ =

the mask should be white image with trasparency.
It will work like this:
+ =

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