OpenCV3.0 gold imread function doesn't work with absolute path on Ubuntu14.04

Question

I use imread function by OpenCV3.0 gold on Ubuntu 14.04, and followed the web to installed OpenCV3.0 But the imread function dosen't work with absolute path.It can work like imread("a.jpg"),but not imread("\home\a\a.jpg") .I want to use the function to read image sequence.Here is my code:

  char filename1[200];
  char filename2[200];
  sprintf(filename1, "/home/image_2/%06d.png", 0);
  sprintf(filename2, "/home/image_2/%06d.png", 1);


  //read the first two frames from the dataset
  Mat img_1_c = imread(filename1);
  Mat img_2_c = imread(filename2);

  if ( !img_1_c.data || !img_2_c.data ) { 
   std::cout<< " --(!) Error reading images " << std::endl; return -1;
   }

There are images in folder a,like 000000.png .When I run it ,it says"--(!) Error reading images".Can someone help me ?Thank you.