Warning: imagepng() [function.imagepng]: Unable to open '' for writing: No such file or directory in /pdf/fpdf/fpdf.php on line 907

Warning: rename(,.png) [function.rename]: No such file or directory in /pdf/fpdf/fpdf.php on line 908

Warning: fopen(.png) [function.fopen]: failed to open stream: No such file or directory in /pdf/fpdf/fpdf.php on line 1562
FPDF error: Can't open image file: .png