I want to use boost to read data from a JSON string that might look something like:
{ "version": 2, "data_type": "alpr_results", "epoch_time": 1534253281728, "img_width": 1920, "img_height": 1080, "processing_time_ms": 271.27728271484, "uuid": "", "error": false, "regions_of_interest": [ { "x": 0, "y": 0, "width": 1920, "height": 1080 } ], "results": [ { "plate": "FRJ7248", "confidence": 94.583724975586, "matches_template": 1, "plate_index": 0, "region": "us-ny", "region_confidence": 88, "processing_time_ms": 94.328330993652, "requested_topn": 25, "coordinates": [ { "x": 1545, "y": 233 }, { "x": 1640, "y": 241 }, { "x": 1635, "y": 284 }, { "x": 1543, "y": 276 } ], "vehicle_region": { "x": 1388, "y": 0, "width": 403, "height": 403 }, "candidates": [ { "plate": "FRJ7248", "confidence": 94.583724975586, "matches_template": 1 }, { "plate": "FRJ724", "confidence": 81.629249572754, "matches_template": 1 }, { "plate": "FR7248", "confidence": 81.344184875488, "matches_template": 0 }, { "plate": "FJ7248", "confidence": 81.199394226074, "matches_template": 0 }, { "plate": "RJ7248", "confidence": 81.19913482666, "matches_template": 0 }, { "plate": "FRJ7246", "confidence": 81.167663574219, "matches_template": 1 }, { "plate": "FRJ7240", "confidence": 81.13761138916, "matches_template": 1 }, { "plate": "FRJ7243", "confidence": 81.127967834473, "matches_template": 1 }, { "plate": "FRJ7245", "confidence": 81.124664306641, "matches_template": 1 }, { "plate": "FRU7248", "confidence": 81.089027404785, "matches_template": 1 }, { "plate": "FBJ7248", "confidence": 81.082328796387, "matches_template": 1 }, { "plate": "FRD7248", "confidence": 81.080703735352, "matches_template": 1 }, { "plate": "ERJ7248", "confidence": 81.068466186523, "matches_template": 1 }, { "plate": "FR724", "confidence": 68.389724731445, "matches_template": 0 }, { "plate": "FJ724", "confidence": 68.244926452637, "matches_template": 0 }, { "plate": "RJ724", "confidence": 68.244659423828, "matches_template": 0 }, { "plate": "FRU724", "confidence": 68.134559631348, "matches_template": 1 }, { "plate": "FBJ724", "confidence": 68.127861022949, "matches_template": 1 }, { "plate": "FRD724", "confidence": 68.126243591309, "matches_template": 1 }, { "plate": "ERJ724", "confidence": 68.113998413086, "matches_template": 1 }, { "plate": "F7248", "confidence": 67.959869384766, "matches_template": 0 }, { "plate": "R7248", "confidence": 67.959594726562, "matches_template": 0 }, { "plate": "FR7246", "confidence": 67.92813873291, "matches_template": 0 }, { "plate": "FR7240", "confidence": 67.898078918457, "matches_template": 0 }, { "plate": "FR7243", "confidence": 67.888442993164, "matches_template": 0 } ] }, { "plate": "T701486C", "confidence": 93.531463623047, "matches_template": 0, "plate_index": 1, "region": "us-ny", "region_confidence": 84, "processing_time_ms": 94.328330993652, "requested_topn": 25, "coordinates": [ { "x": 1005, "y": 407 }, { "x": 1101, "y": 400 }, { "x": 1102, "y": 454 }, { "x": 1007, "y": 462 } ], "vehicle_region": { "x": 782, "y": 69, "width": 543, "height": 543 }, "candidates": [ { "plate": "T701486C", "confidence": 93.531463623047, "matches_template": 0 }, { "plate": "T70T486C", "confidence": 82.387817382812, "matches_template": 0 }, { "plate": "T70486C", "confidence": 82.198287963867, "matches_template": 0 }, { "plate": "T70I486C", "confidence": 82.151023864746, "matches_template": 0 }, { "plate": "701486C", "confidence": 82.046699523926, "matches_template": 0 }, { "plate": "T70146C", "confidence": 81.921669006348, "matches_template": 0 }, { "plate": "7701486C", "confidence": 81.844429016113, "matches_template": 0 }, { "plate": "1701486C", "confidence": 81.822814941406, "matches_template": 0 }, { "plate": "T701466C", "confidence": 81.808143615723, "matches_template": 0 }, { "plate": "70T486C", "confidence": 70.903053283691, "matches_template": 0 }, { "plate": "T70T46C", "confidence": 70.778022766113, "matches_template": 0 }, { "plate": "70486C", "confidence": 70.713523864746, "matches_template": 0 }, { "plate": "770T486C", "confidence": 70.700782775879, "matches_template": 0 }, { "plate": "170T486C", "confidence": 70.679168701172, "matches_template": 0 }, { "plate": "70I486C", "confidence": 70.666259765625, "matches_template": 0 }, { "plate": "T70T466C", "confidence": 70.664497375488, "matches_template": 0 }, { "plate": "T7046C", "confidence": 70.588493347168, "matches_template": 0 }, { "plate": "T70I46C", "confidence": 70.541229248047, "matches_template": 0 }, { "plate": "770486C", "confidence": 70.511253356934, "matches_template": 0 }, { "plate": "170486C", "confidence": 70.489639282227, "matches_template": 0 }, { "plate": "T70466C", "confidence": 70.474967956543, "matches_template": 0 }, { "plate": "770I486C", "confidence": 70.463996887207, "matches_template": 0 }, { "plate": "170I486C", "confidence": 70.442375183105, "matches_template": 0 }, { "plate": "70146C", "confidence": 70.436904907227, "matches_template": 0 }, { "plate": "T70I466C", "confidence": 70.427703857422, "matches_template": 0 } ] } ] } All I'm interested in for now is the "plate" in "results", i.e. FRJ7248 and T701486C. So far, I've got this:
int alpr_json_decode(std::string json) { try { std::stringstream ss; ss << json; boost::property_tree::ptree pt; boost::property_tree::read_json(ss,pt); BOOST_FOREACH(boost::property_tree::ptree::value_type &v, pt.get_child("results.plate")) { assert(v.first.empty()); std::cout << v.second.data() << std::endl; } } catch(std::exception const& e) { std::cerr <<e.what() << std::endl; } return -1; } And I get No such node (results.plate). Why, what am I doing wrong here?
I've also tried .get_child("results") which returns nothing.
