The program prints perfectly when there is no License Plate in the frame, but when there is, I get the SyntaxError
. Node.js and OpenALPR is installed. Photos are successfully being taken also.
const PiCamera = require('pi-camera');
function getRandomInt(max) {
return Math.floor(Math.random() * Math.floor(max));
}
setInterval(function() {
var path = './' + getRandomInt(500) + '.jpg';
const myCamera = new PiCamera({
mode: 'photo',
output: path,
width: 1920,
height: 1080,
nopreview: false,
});
myCamera.snap()
.then((result) => {
var exec = require('child_process').exec;
var cmd = 'alpr -c eu -n 1 --json ' + path;
exec(cmd, function(error, stdout, stderr) {
var data = JSON.parse(stdout);
if (data.results.length > 0) {
console.log(data.results[0].plate);
} else {
console.log("\n\n\nNo license plate found.\n\n");
}
});
console.log(result);
})
.catch((error) => {
console.log(error);
});
}, 2e3);
The error and where it occurs is:
undefined:1
SyntaxError: Unexpected end of JSON input
at JSON.parse (<anonymous>)
at /home/pi/Project/project.js:28:33
at ChildProcess.exithandler (child_process.js:301:5)
at ChildProcess.emit (events.js:189:13)
at maybeClose (internal/child_process.js:970:16)
at Socket.stream.socket.on (internal/child_process.js:389:11)
at Socket.emit (events.js:189:13)
at Pipe._handle.close (net.js:600:12)
Output of console.log(stdout);
before var data
declaration:
{"version":2,"data_type":"alpr_results","epoch_time":1588355061888,"img_width":1920,"img_height":1080,"processing_time_ms":1447.340698,"regions_of_interest":[],"results":[]}
There is a space at the end of the JSON.
try {
var data = JSON.parse(stdout.trim())
} catch (e) {
console.error('Failed to Parse JSON!', e)
}