pdf417decode imagefile|stringfile|-i PDF417decode takes one parameter, which can be one of the following (1) the path of the image file. The file can be JPEG, PNG, TIF or GIF. (2) a text file that contains the barcode string (generated by PDF417 Fontware & Writer SDK 4). The file name must have .txt as the extension. (3) -i, which means that the barcode string will be entered through input. The following commands are valid: 1. decode image file test-pdf417-scan.png pdf417decode test-pdf417-scan.png 2. decode barcode string, stored in test-barstr.txt pdf417decode test-barstr.txt 3. decode barcode string, entered through std input (C stdin) pdf417decode -i .