Add PNG support

index.js

@@ -59,7 +59,7 @@ app.get('/', (req, res) => {
       - Prints IPP attributes
     - GET /printers/:name/jobs
       - Prints IPP jobs
-    - POST /print?printer=:name (body: application/pdf)
+    - POST /print?printer=:name (body: application/pdf or image/png)
       - Prints a PDF
       - ?printer= printer name or alias (case insensitive)
       - ?copies= (optional) number of copies (1-10 allowed)
@@ -132,8 +132,13 @@ app.post('/print', bodyParser.raw({ type: '*/*', limit: 10_000_000 }), (req, res
   if (!body || !body.length) {
     res.status(400).send("No data received, please send a PDF")
     return
-  } else if (body.subarray(0, 4).toString() !== "%PDF") {
-    res.status(415).send("Data does not look like a PDF, please send a PDF")
+  }
+
+  const isPDF = body.subarray(0, 4).toString() === "%PDF"
+  const isPNG = body.subarray(0, 8).equals(Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]))
+
+  if (!isPDF && !isPNG) {
+    res.status(415).send("Unsupported media type, only PDF and PNG are supported")
     return
   }
 
@@ -147,7 +152,7 @@ app.post('/print', bodyParser.raw({ type: '*/*', limit: 10_000_000 }), (req, res
   // send print job
   const msg = {
     "operation-attributes-tag": {
-      "document-format": "application/pdf",
+      "document-format": isPNG ? "image/png" : "application/pdf",
     },
     "job-attributes-tag": {
       "copies": copies,