如何在Java中将NA值表示为空白像素（白色）？

Question

我正在使用Java HeatMap库（http://www.mbeckler.org/heatMap/）为我的数据生成heatMap。 我正在使用具有NA值的daatset。所以，基本上我不想为具有NA值的像素使用颜色（白色）。但不幸的是，这个库不支持具有NA值的数据，我得到的是具有基本颜色的图像块图。我试图查看源代码，以便进行一些更改。在代码中，使用drawData()方法为bufferedImage中的每个像素着色（可能！）。有人可以帮助我如何实现对NA值的支持并向他们显示无颜色？我对BufferedImage和Graphics2D班没有经验。

这里是从库的源代码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); 
      } 
     } 
    } 

样本数据，可以发现：http://www.filedropper.com/data_13

所以，这是它的外观的时刻：

来自Java的：

从R：

请忽略这两个图像

Answer 1

由于BufferedImage为ARGB创建的方向，你可能只是不应该是不确定的像素画什么，他们将保持透明。喜欢的东西：

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(); 
    } 
} 

我也处置Graphics2D实例，以避免资源泄漏。