如何在Java中將NA值表示爲空白像素（白色）？

Question

我正在使用Java HeatMap庫（http://www.mbeckler.org/heatMap/）爲我的數據生成heatMap。 我正在使用具有NA值的daatset。所以，基本上我不想爲具有NA值的像素使用顏色（白色）。但不幸的是，這個庫不支持具有NA值的數據，我得到的是具有基本顏色的圖像塊圖。我試圖查看源代碼，以便進行一些更改。在代碼中，使用drawData()方法爲bufferedImage中的每個像素着色（可能！）。有人可以幫助我如何實現對NA值的支持並向他們顯示無顏色？我對BufferedImage和Graphics2D班沒有經驗。

這裏是從庫的源代碼drawData()方法：

/** 
    * Creates a BufferedImage of the actual data plot. 
    * 
    * After doing some profiling, it was discovered that 90% of the drawing 
    * time was spend drawing the actual data (not on the axes or tick marks). 
    * Since the Graphics2D has a drawImage method that can do scaling, we are 
    * using that instead of scaling it ourselves. We only need to draw the 
    * data into the bufferedImage on startup, or if the data or gradient 
    * changes. This saves us an enormous amount of time. Thanks to 
    * Josh Hayes-Sheen (grey@grevian.org) for the suggestion and initial code 
    * to use the BufferedImage technique. 
    * 
    * Since the scaling of the data plot will be handled by the drawImage in 
    * paintComponent, we take the easy way out and draw our bufferedImage with 
    * 1 pixel per data point. Too bad there isn't a setPixel method in the 
    * Graphics2D class, it seems a bit silly to fill a rectangle just to set a 
    * single pixel... 
    * 
    * This function should be called whenever the data or the gradient changes. 
    */ 
    private void drawData() 
    { 

     // System.out.println("Column: " + data.length + " row: " + data[0].length); 
     bufferedImage = new BufferedImage(data.length,data[0].length, BufferedImage.TYPE_INT_ARGB); 
     bufferedGraphics = bufferedImage.createGraphics(); 

     for (int x = 0; x < data.length; x++) 
     { 
      for (int y = 0; y < data[0].length; y++) 
      { 
       bufferedGraphics.setColor(colors[dataColorIndices[x][y]]); 
       bufferedGraphics.fillRect(x, y, 1, 1); 
      } 
     } 
    } 

樣本數據，可以發現：http://www.filedropper.com/data_13

所以，這是它的外觀的時刻：

來自Java的：

從R：

請忽略這兩個圖像

Answer 1

由於BufferedImage爲ARGB創建的方向，你可能只是不應該是不確定的像素畫什麼，他們將保持透明。喜歡的東西：

public static int NA = ...; 

private void drawData() 
{ 
    bufferedImage = new BufferedImage(data.length,data[0].length, BufferedImage.TYPE_INT_ARGB); 
    Graphics2D bufferedGraphics = bufferedImage.createGraphics(); 
    try { 
     for (int x = 0; x < data.length; x++) 
     { 
      for (int y = 0; y < data[0].length; y++) 
      { 
       int colorIndex = dataColorIndices[x][y]; 
       if (colorIndex != NA) { 
        bufferedGraphics.setColor(colors[colorIndex]); 
        bufferedGraphics.fillRect(x, y, 1, 1); 
       } 
// Alternate flow, if you really want the pixels to be white 
//    else { 
//     bufferedGraphics.setColor(Color.WHITE); 
//     bufferedGraphics.fillRect(x, y, 1, 1); 
//    } 
      } 
     } 
    } 
    finally { 
     bufferedGraphics.dispose(); 
    } 
} 

我也處置Graphics2D實例，以避免資源泄漏。