pdfbox

[??????]

dear,    I have a trouble about PDFToImage.
    If i code as below , the image doesn't have color.
    String pdfPath = "C:/Users/jinlonghuang/Desktop/tmp.pdf";
         
          String [] args_1 =  new String[5];
          args_1[0]  = "-outputPrefix";
          args_1[1]  = "C:/Users/jinlonghuang/Desktop/pdfdemo2";
          args_1[2]  = "-imageType";
          args_1[3]  = "jpg";
          args_1[4]  = pdfPath;


    If i code as below , the image will couldn't be created.


    String [] args_1 =  new String[7];
          args_1[0]  = "-outputPrefix";
          args_1[1]  = "C:/Users/jinlonghuang/Desktop/pdfdemo2";
          args_1[2]  = "-imageType";
          args_1[3]  = "jpg";
          args_1[4]  = "-color";
          args_1[5]  = "rgb";
          args_1[6]  = pdfPath;

   
    My pdfbox version is PDFBox-0.7.3.
    Can you help me?
    Best wishes!