WIP - add extractor, generate snippet_data

node_modules/probe-image-size/lib/parse_stream/jpeg.js

@@ -0,0 +1,117 @@
+'use strict';
+
+
+var ParserStream = require('../common').ParserStream;
+
+
+// part of parseJpegMarker called after skipping initial FF
+function parseJpegMarker_afterFF(parser, callback) {
+  parser._bytes(1, function (data) {
+    var code = data[0];
+
+    if (code === 0xFF) {
+      // padding byte, skip it
+      parseJpegMarker_afterFF(parser, callback);
+      return;
+    }
+
+    // standalone markers, according to JPEG 1992,
+    // http://www.w3.org/Graphics/JPEG/itu-t81.pdf, see Table B.1
+    if ((0xD0 <= code && code <= 0xD9) || code === 0x01) {
+      callback(code, 0);
+      return;
+    }
+
+    // the rest of the unreserved markers
+    if (0xC0 <= code && code <= 0xFE) {
+      parser._bytes(2, function (length) {
+        callback(code, length.readUInt16BE(0) - 2);
+      });
+      return;
+    }
+
+    // unknown markers
+    callback();
+  });
+}
+
+
+function parseJpegMarker(parser, callback) {
+  parser._bytes(1, function (data) {
+    if (data[0] !== 0xFF) {
+      // not a JPEG marker
+      callback();
+      return;
+    }
+
+    parseJpegMarker_afterFF(parser, callback);
+  });
+}
+
+
+function getJpegSize(parser) {
+  parseJpegMarker(parser, function (code, length) {
+    if (!code || length < 0) {
+      // invalid jpeg
+      parser._skipBytes(Infinity);
+      parser.push(null);
+      return;
+    }
+
+    if (code === 0xD9 /* EOI */ || code === 0xDA /* SOS */) {
+      // end of the datastream
+      parser._skipBytes(Infinity);
+      parser.push(null);
+      return;
+    }
+
+    if (length <= 0) {
+      // e.g. empty comment
+      getJpegSize(parser);
+      return;
+    }
+
+    if (length >= 5 &&
+        (0xC0 <= code && code <= 0xCF) &&
+        code !== 0xC4 && code !== 0xC8 && code !== 0xCC) {
+
+      parser._bytes(length, function (data) {
+        parser._skipBytes(Infinity);
+
+        parser.push({
+          width:  data.readUInt16BE(3),
+          height: data.readUInt16BE(1),
+          type: 'jpg',
+          mime: 'image/jpeg',
+          wUnits: 'px',
+          hUnits: 'px'
+        });
+
+        parser.push(null);
+      });
+      return;
+    }
+
+    parser._skipBytes(length, function () {
+      getJpegSize(parser);
+    });
+  });
+}
+
+
+module.exports = function () {
+  var parser   = new ParserStream();
+
+  parser._bytes(2, function (data) {
+    if (data[0] !== 0xFF || data[1] !== 0xD8) {
+      // first marker of the file MUST be 0xFFD8
+      parser._skipBytes(Infinity);
+      parser.push(null);
+      return;
+    }
+
+    getJpegSize(parser);
+  });
+
+  return parser;
+};