Takes a Unity Texture2D and get a Google Cloud vision annotation response. Please replace api key accordingly and *make sure Google Cloud billing is enabled*

Image2GoogleVision.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace GoogleCloudVision {

    [System.Serializable]
    public class AnnotateImageRequests
    {
        public List<AnnotateImageRequest> requests;
    }

    [System.Serializable]
    public class AnnotateImageRequest
    {
        public Image image;
        public List<Feature> features;
    }

    [System.Serializable]
    public class Image
    {
        public string content;
    }

    [System.Serializable]
    public class Feature
    {
        public string type;
        public int maxResults;
    }

    public enum FeatureType
    {
        TYPE_UNSPECIFIED,
        FACE_DETECTION,
        LANDMARK_DETECTION,
        LOGO_DETECTION,
        LABEL_DETECTION,
        TEXT_DETECTION,
        SAFE_SEARCH_DETECTION,
        IMAGE_PROPERTIES
    }

    [System.Serializable]
    public class AnnotateImageResponses
    {
        public List<AnnotateImageResponse> responses;
    }

    [System.Serializable]
    public class AnnotateImageResponse
    {
        public List<FaceAnnotation> faceAnnotations;
        public List<EntityAnnotation> landmarkAnnotations;
        public List<EntityAnnotation> logoAnnotations;
        public List<EntityAnnotation> labelAnnotations;
        public List<EntityAnnotation> textAnnotations;
    }

    [System.Serializable]
    public class FaceAnnotation
    {
        public BoundingPoly boundingPoly;
        public BoundingPoly fdBoundingPoly;
        public List<Landmark> landmarks;
        public float rollAngle;
        public float panAngle;
        public float tiltAngle;
        public float detectionConfidence;
        public float landmarkingConfidence;
        public string joyLikelihood;
        public string sorrowLikelihood;
        public string angerLikelihood;
        public string surpriseLikelihood;
        public string underExposedLikelihood;
        public string blurredLikelihood;
        public string headwearLikelihood;
    }

    [System.Serializable]
    public class EntityAnnotation
    {
        public string mid;
        public string locale;
        public string description;
        public float score;
        public float confidence;
        public float topicality;
        public BoundingPoly boundingPoly;
        public List<LocationInfo> locations;
        public List<Property> properties;
    }

    [System.Serializable]
    public class Vertex
    {
        public float x;
        public float y;
    }


    [System.Serializable]
    public class BoundingPoly
    {
        public List<Vertex> vertices;
    }

    [System.Serializable]
    public class Position
    {
        public float x;
        public float y;
        public float z;
    }

    [System.Serializable]
    public class Landmark
    {
        public string type;
        public Position position;
    }

    [System.Serializable]
    public class Property
    {
        string name;
        string value;
    }

    [RequireComponent(typeof(WWWPost))]
    public class Image2GoogleVision : MonoBehaviour
    {
        public Texture2D texture;
        public int maxResults = 10;

        public FeatureType featureType = FeatureType.LABEL_DETECTION;

        private void Awake()
        {
            wp = GetComponent<WWWPost>();
        }

        private void Start()
        {
           

            SendToGV(texture);
        }

        public void SendToGV(Texture2D texture2D)
        {
            string url = "https://vision.googleapis.com/v1/images:annotate";
            string key =  


            // texture2D.Apply(false); // Not required. Because we do not need to be uploaded it to GPU
            byte[] jpg = texture2D.EncodeToJPG();
            string base64 = System.Convert.ToBase64String(jpg);
#if UNITY_WEBGL
            Application.ExternalCall("post", this.gameObject.name, "OnSuccessFromBrowser", "OnErrorFromBrowser", this.url + this.apiKey, base64, this.featureType.ToString(), this.maxResults);
#else

            AnnotateImageRequests requests = new AnnotateImageRequests();
            requests.requests = new List<AnnotateImageRequest>();

            AnnotateImageRequest request = new AnnotateImageRequest();
            request.image = new Image();
            request.image.content = base64;
            request.features = new List<Feature>();

            Feature feature = new Feature();
            feature.type = this.featureType.ToString();
            feature.maxResults = this.maxResults;

            request.features.Add(feature);

            requests.requests.Add(request);

            string jsonData = JsonUtility.ToJson(requests, false);
            if (jsonData != string.Empty)
            {

               byte[] postData = System.Text.Encoding.Default.GetBytes(jsonData);
                url += "?key=" + key; print(url);
                wp.Post(url, postData, ProcessReturn);//,WWWPost.SignHeaders(key,true) );

            }
        }

        void ProcessReturn( string t)
        {
            print(t);
            Sample_OnAnnotateImageResponses(JsonUtility.FromJson<AnnotateImageResponses>(t));
        }

        WWWPost wp;


        void Sample_OnAnnotateImageResponses(AnnotateImageResponses responses)
        {
            if (responses.responses.Count > 0)
            {
                if (responses.responses[0].labelAnnotations != null && responses.responses[0].labelAnnotations.Count > 0)
                {
                   // Debug.Log("desc: " + responses.responses[0].labelAnnotations[0].description);
                   for(int i=0;i< responses.responses[0].labelAnnotations.Count; i++)
                    {
                        string desc = responses.responses[0].labelAnnotations[i].description;
                        float conf = (responses.responses[0].labelAnnotations[i].score * 100f);//.ToString("F4");
                        print(desc + " " + conf);
                    }
                }
            }
        }

#endif 
    } 
   

}