Android给任何view添加全屏倾斜水印

 public static Bitmap getMarkTextBitmap(Context gContext, String gText, int width, int height, boolean is4Showing){
//  Bitmap bitmap = ACache.get(gContext).getAsBitmap(gText);
//  if (is4Showing && bitmap != null){
//   return bitmap;
//  }

  float textSize;
  float inter;
  if (is4Showing){
   textSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 18, gContext.getResources().getDisplayMetrics());
   inter = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 25, gContext.getResources().getDisplayMetrics());
  } else {
   textSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 54, gContext.getResources().getDisplayMetrics());
   inter = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 75, gContext.getResources().getDisplayMetrics());
  }

  int sideLength;
  if (width > height) {
   sideLength = (int) Math.sqrt(2*(width * width));
  } else {
   sideLength = (int) Math.sqrt(2*(height * height));
  }


  Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
  Rect rect = new Rect();
  paint.setTextSize(textSize);
  //获取文字长度和宽度
  paint.getTextBounds(gText, 0, gText.length(), rect);

  int strwid = rect.width();
  int strhei = rect.height();

  Bitmap markBitmap = null;
  try {
   markBitmap = Bitmap.createBitmap(sideLength, sideLength, Bitmap.Config.ARGB_4444);
   Canvas canvas = new Canvas(markBitmap);
   //创建透明画布
   canvas.drawColor(Color.TRANSPARENT);

   paint.setColor(Color.BLACK);
   paint.setAlpha((int) (0.1*255f));
   // 获取跟清晰的图像采样
   paint.setDither(true);
   paint.setFilterBitmap(true);

   //先平移，再旋转才不会有空白，使整个图片充满
   if (width > height) {
    canvas.translate(width - sideLength - inter, sideLength - width + inter);
   } else {
    canvas.translate(height - sideLength - inter, sideLength - height + inter);
   }

   //将该文字图片逆时针方向倾斜45度
   canvas.rotate(-45);

   for (int i =0; i <= sideLength; ){
    int count = 0;
    for (int j =0; j <= sideLength; count++){
     if (count % 2 == 0){
      canvas.drawText(gText, i, j, paint);
     } else {
      //偶数行进行错开
      canvas.drawText(gText, i + strwid/2, j, paint);
     }
     j = (int) (j + inter + strhei);
    }
    i = (int) (i + strwid + inter);
   }
   canvas.save(Canvas.ALL_SAVE_FLAG);
//  ACache.get(gContext).put(gText, markBitmap);
  } catch (OutOfMemoryError e) {
   Util.LOGD(TAG, e);
   if(markBitmap != null && !markBitmap.isRecycled()){
    markBitmap.recycle();
    markBitmap = null;
   }
  }

  return markBitmap;
 }

 /**
  * 获得文字水印的图片
  * @param width
  * @param height
  * @return
  */
 public static Drawable getMarkTextBitmapDrawable(Context gContext, String gText, int width, int height, boolean is4Showing){
  Bitmap bitmap = getMarkTextBitmap(gContext, gText, width, height, is4Showing);
  if (bitmap != null){
   BitmapDrawable drawable = new BitmapDrawable(gContext.getResources(), bitmap);
   drawable.setTileModeXY(Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
   drawable.setDither(true);
//   Drawable drawableFinal = drawable.getConstantState().newDrawable();
//   if(!bitmap.isRecycled()){
//    bitmap.recycle();
//    bitmap = null;
//   }
//
   return drawable;
  }
  return null;
 }