由jfreechart创建的PNG JPEG文件的色差

Question

我在jsp中使用jfreechart创建了一个条形图

String path=null;
 DefaultCategoryDataset dataset = new DefaultCategoryDataset(); 
 dataset.setValue(6, "Profit1", "Jane"); 
 dataset.setValue(3, "Profit2", "Jane"); 
 dataset.setValue(7, "Profit1", "Tom"); 
 dataset.setValue(10, "Profit2", "Tom"); 
 dataset.setValue(8, "Profit1", "Jill"); 
 dataset.setValue(8, "Profit2", "Jill"); 
 dataset.setValue(5, "Profit1", "John"); 
 dataset.setValue(6, "Profit2", "John"); 
 dataset.setValue(12, "Profit1", "Fred"); 
 dataset.setValue(5, "Profit2", "Fred");

 // Profit1, Profit2 represent the row keys 
 // Jane, Tom, Jill, etc. represent the column keys

 JFreeChart chart = ChartFactory.createBarChart3D( 
    "Comparison between Salesman",  // Chart name 
    "Salesman",                     // X axis label 
    "Value ($)",                    // Y axis value 
    dataset,                        // data set 
    PlotOrientation.VERTICAL, 
    true, true, false);
 chart.setBackgroundPaint(Color.white);  
 // Set the background color of the chart    

 // Creating a JPEG image 
 try 
 { 
     path= request.getRealPath("images")+"/myChart.jpg";
    ChartUtilities.saveChartAsJPEG(new File(path), chart, 500, 300);

    System.out.println("image created");
    //path=path.replace("\\","/");
 } 
 catch (IOException e) 
 { 
    System.err.println("Problem occurred creating chart."); 
 }

创建的jpeg图像

保存为png图像时

 path= request.getRealPath("images")+"/myChart.png";
        ChartUtilities.saveChartAsPNG(new File(path), chart, 500, 300);

我无法找到我出错的地方，我需要像png图像一样的jpeg图像。 有什么想法吗？