在屏幕上绘制而不显示颜色，并保存图像

我需要在屏幕上绘图，并将其捕获并显示在另一个活动中，但我不需要显示绘图的颜色，即只显示手指会移动，没有人能够看到它的绘制。在屏幕上绘制而不显示颜色，并保存图像

不知道如何在这种情况下取得进展。我做得出这样的，但这是正常的，你所看到的一些一个是借鉴：

class SignatureView extends View { 

     private static final float STROKE_WIDTH = 5f; 

     private static final float HALF_STROKE_WIDTH = STROKE_WIDTH/2; 

     private Paint paint = new Paint(); 
     private Path path = new Path(); 

     private float lastTouchX; 
     private float lastTouchY; 
     private final RectF dirtyRect = new RectF(); 

     public SignatureView(Context context) { 
     super(context); 

     paint.setAntiAlias(true); 
     paint.setColor(Color.WHITE); 
     paint.setStyle(Paint.Style.STROKE); 
     paint.setStrokeJoin(Paint.Join.ROUND); 
     paint.setStrokeWidth(STROKE_WIDTH); 
     } 

     public void clear() { 


     path.reset(); 
     AddView(); 

     invalidate(); 
     } 

     @Override 
     protected void onDraw(Canvas canvas) { 
     canvas.drawPath(path, paint); 
     } 

     @Override 
     public boolean onTouchEvent(MotionEvent event) { 
     float eventX = event.getX(); 
     float eventY = event.getY(); 

     switch (event.getAction()) { 
      case MotionEvent.ACTION_DOWN: 
      path.moveTo(eventX, eventY); 
      lastTouchX = eventX; 
      lastTouchY = eventY; 
      return true; 

      case MotionEvent.ACTION_MOVE: 
      case MotionEvent.ACTION_UP: 
      resetDirtyRect(eventX, eventY); 

      int historySize = event.getHistorySize(); 
      for (int i = 0; i < historySize; i++) { 
       float historicalX = event.getHistoricalX(i); 
       float historicalY = event.getHistoricalY(i); 
       expandDirtyRect(historicalX, historicalY); 
       path.lineTo(historicalX, historicalY); 
      } 

      path.lineTo(eventX, eventY); 
      break; 

      default: 
      debug("Ignored touch event: " + event.toString()); 
      return false; 
     } 

     invalidate(
      (int) (dirtyRect.left - HALF_STROKE_WIDTH), 
      (int) (dirtyRect.top - HALF_STROKE_WIDTH), 
      (int) (dirtyRect.right + HALF_STROKE_WIDTH), 
      (int) (dirtyRect.bottom + HALF_STROKE_WIDTH)); 

     lastTouchX = eventX; 
     lastTouchY = eventY; 

     return true; 
     } 

     private void expandDirtyRect(float historicalX, float historicalY) { 
     if (historicalX < dirtyRect.left) { 
      dirtyRect.left = historicalX; 
     } else if (historicalX > dirtyRect.right) { 
      dirtyRect.right = historicalX; 
     } 
     if (historicalY < dirtyRect.top) { 
      dirtyRect.top = historicalY; 
     } else if (historicalY > dirtyRect.bottom) { 
      dirtyRect.bottom = historicalY; 
     } 
     } 


     private void resetDirtyRect(float eventX, float eventY) { 

     dirtyRect.left = Math.min(lastTouchX, eventX); 
     dirtyRect.right = Math.max(lastTouchX, eventX); 
     dirtyRect.top = Math.min(lastTouchY, eventY); 
     dirtyRect.bottom = Math.max(lastTouchY, eventY); 
     } 
    }

甚至试图油漆阿尔法设置为0，但没有用它设置透明图像。

来源

2013-03-16 zaiff

请尝试以下变化

paint.setColor(Color.TRANSPARENT);

来源

2013-03-16 10:45:25 Rekha

在屏幕上绘制而不显示颜色，并保存图像

回答

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