更改位圖背景圖像/顏色，還是使其透明？

Question

我一直在關注這個繪圖教程，而且我做得很好，並對它進行了很多修改。

唯一的問題，我無法弄清楚如何改變位圖/畫布的顏色或圖像。它是黑色的，我希望它是白色的，設置爲名爲bg.png的圖像，或者是透明的。任何幫助讚賞。這是我的java類/位圖。

import android.content.Context; 
import android.graphics.*; 
import android.os.Handler; 
import android.os.Message; 
import android.util.AttributeSet; 
import android.util.Log; 
import android.view.SurfaceHolder; 
import android.view.SurfaceView; 


import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Iterator; 
import java.util.List; 


public class DrawingSurface extends SurfaceView implements SurfaceHolder.Callback { 
    private Boolean _run; 
    protected DrawThread thread; 
    private Bitmap mBitmap; 
    public boolean isDrawing = true; 
    public DrawingPath previewPath; 


private CommandManager commandManager; 

public DrawingSurface(Context context, AttributeSet attrs) { 
    super(context, attrs); 

    getHolder().addCallback(this); 


    commandManager = new CommandManager(); 
    thread = new DrawThread(getHolder()); 
} 

private Handler previewDoneHandler = new Handler(){ 
    @Override 
    public void handleMessage(Message msg) { 
     isDrawing = false; 
    } 
}; 

class DrawThread extends Thread{ 
    private SurfaceHolder mSurfaceHolder; 


    public DrawThread(SurfaceHolder surfaceHolder){ 
     mSurfaceHolder = surfaceHolder; 

    } 

    public void setRunning(boolean run) { 
     _run = run; 
    } 


    @Override 
    public void run() { 
     Canvas canvas = null; 
     while (_run){ 
      if(isDrawing == true){ 
       try{ 
        canvas = mSurfaceHolder.lockCanvas(null); 
        if(mBitmap == null){ 
         mBitmap = Bitmap.createBitmap (1, 1, Bitmap.Config.ARGB_8888); 
        } 
        final Canvas c = new Canvas (mBitmap); 

        c.drawColor(0, PorterDuff.Mode.CLEAR); 
        canvas.drawColor(0, PorterDuff.Mode.CLEAR); 


        commandManager.executeAll(c,previewDoneHandler); 
        previewPath.draw(c); 

        canvas.drawBitmap (mBitmap, 0, 0,null); 
       } finally { 
        mSurfaceHolder.unlockCanvasAndPost(canvas); 
       } 


      } 

     } 

    } 
} 


public void addDrawingPath (DrawingPath drawingPath){ 
    commandManager.addCommand(drawingPath); 
} 

public boolean hasMoreRedo(){ 
    return commandManager.hasMoreRedo(); 
} 

public void redo(){ 
    isDrawing = true; 
    commandManager.redo(); 


} 

public void undo(){ 
    isDrawing = true; 
    commandManager.undo(); 
} 

public boolean hasMoreUndo(){ 
    return commandManager.hasMoreUndo(); 
} 

public Bitmap getBitmap(){ 
    return mBitmap; 
} 


public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { 
    // TODO Auto-generated method stub 
    mBitmap = Bitmap.createBitmap (width, height, Bitmap.Config.ARGB_8888);; 
} 


public void surfaceCreated(SurfaceHolder holder) { 
    // TODO Auto-generated method stub 
    thread.setRunning(true); 
    thread.start(); 
} 

public void surfaceDestroyed(SurfaceHolder holder) { 
    // TODO Auto-generated method stub 
    boolean retry = true; 
    thread.setRunning(false); 
    while (retry) { 
     try { 
      thread.join(); 
      retry = false; 
     } catch (InterruptedException e) { 
      // we will try it again and again... 
     } 
    } 
} 

}

Answer 1

此鏈接可以幫助它展示瞭如何做藍綠或藍屏，這是如何在Java中的圖像背景透明：

-howto-chromakey