Generating a PNG image of chart from json file - highcharts

Question

I am displaying the contents of a large database in a Highcharts chart and I would like to capture the image of the graph automatically, say at 9pm daily, and save the image in a file. I have tried to install the server-side export server solution, but I have been unable to make it work on the raspberry pi.
As an alternative, I have captured the json used to generate the graph in a file. Can I send the file to Highcharts and get a PNG image in return? How, exactly, should I do this?
Thanks.
The json file contains the following. This is exactly the same json that is passed to the browser and results in a proper graph:
[{
"name": "Consumed",
"data": [
[1521612002000, 668],
[1521612182000, 668],
[1521634338000, 487]
]
}, {
"name": "Paid For",
"data": [
[1521612002000, 668],
[1521612182000, 668],
[1521634338000, 75]
]
}, {
"name": "Produced",
"data": [
[1521612002000, 0],
[1521612182000, 0],
[1521634338000, 412]
]
}, {
"name": "Paid For kWh",
"data": [
[1521612002000, null],
[1521615425000, 0.6118],
[1521634338000, null]
]
}]
I have tried the following curl command:
curl -H "Content-Type: application/json" -X POST -d '{"infile": combined_readings.json}' http://export.highcharts.com > file.png
It resulted in the following error:
SyntaxError: Unexpected token c in JSON at position 11<br> at Object.parse (native)<br> at parse (/var/app/current/node_modules/highcharts-export-server/node_modules/body-parser/lib/types/json.js:88:17)<br> at /var/app/current/node_modules/highcharts-export-server/node_modules/body-parser/lib/read.js:116:18<br> at invokeCallback (/var/app/current/node_modules/highcharts-export-server/node_modules/raw-body/index.js:262:16)<br> at done (/var/app/current/node_modules/highcharts-export-server/node_modules/raw-body/index.js:251:7)<br> at IncomingMessage.onEnd (/var/app/current/node_modules/highcharts-export-server/node_modules/raw-body/index.js:307:7)<br> at emitNone (events.js:86:13)<br> at IncomingMessage.emit (events.js:185:7)<br> at endReadableNT (_stream_readable.js:974:12)<br> at _combinedTickCallback (internal/process/next_tick.js:74:11)
With the help of highcharts support I was able to resolve several issues:
- the curl command requires a json string (as noted in the comments)
- the json string needs to be reformatted from that required by the browser
Here is the reformatted json string:
{
"series": [{
"name": "Consumed",
"data": [
[1521612002000, 668],
[1521612182000, 668],
[1521634338000, 487]
]
}, {
"name": "Paid For",
"data": [
[1521612002000, 668],
[1521612182000, 668],
[1521634338000, 75]
]
}, {
"name": "Produced",
"data": [
[1521612002000, 0],
[1521612182000, 0],
[1521634338000, 412]
]
}, {
"name": "Paid For kWh",
"data": [
[1521612002000, null],
[1521615425000, 0.6118],
[1521634338000, null]
]
}]
}
The curl command required looks like this:
curl -H "Content-Type: application/json" -X POST -d "{\"infile\": \"{series: [{name: 'Consumed',data: [[1521612002000, 668],[1521612182000, 668],[1521634338000, 487]]}, {name: 'Paid For',data: [[1521612002000, 668],[1521612182000, 668],[1521634338000, 75]]}, {name: 'Produced',data: [[1521612002000, 0],[1521612182000, 0],[1521634338000, 412]]}, {name: 'Paid For kWh',data: [[1521612002000, null],[1521615425000, 0.6118],[1521634338000, null]]}]}\"}" export.highcharts.com > chart.png