Processing images asynchronously

This tutorial demonstrates using Knative serving, Cloud Vision API, and ImageMagick to detect and blur offensive images uploaded to a Cloud Storage bucket. This tutorial builds on the tutorial Using Pub/Sub with Knative serving.

This tutorial walks through modifying an existing sample app. You can also download the completed sample if you want.

Setting up gcloud defaults

To configure gcloud with defaults for your Knative serving service:

1. Set your default project:

   gcloud config set project PROJECT_ID

   Replace PROJECT_ID with the name of the project you use for this tutorial.

2. Configure gcloud for your cluster:

   gcloud config set run/platform gke
   gcloud config set run/cluster CLUSTER-NAME
   gcloud config set run/cluster_location REGION

   Replace:

   • CLUSTER-NAME with the name you used for your cluster,
   • REGION with the supported cluster location of your choice.

Understanding the sequence of operations

The flow of data in this tutorial follows these steps:

1. A user uploads an image to a Cloud Storage bucket.
2. Cloud Storage publishes a message about the new file to Pub/Sub.
3. Pub/Sub pushes the message to the Knative serving service.
4. The Knative serving service retrieves the image file referenced in the Pub/Sub message.
5. The Knative serving service uses the Cloud Vision API to analyze the image.
6. If violent or adult content is detected, the Knative serving service uses ImageMagick to blur the image.
7. The Knative serving service uploads the blurred image to another Cloud Storage bucket for use.

Subsequent use of the blurred image is left as an exercise for the reader.

Setting up Cloud Storage buckets

1. Create a Cloud Storage bucket for uploading images, where INPUT_BUCKET_NAME is a globally unique bucket name:

   gcloud storage buckets create gs://INPUT_BUCKET_NAME

   The Knative serving service only reads from this bucket.

2. Create a second Cloud Storage bucket to receive blurred images, where BLURRED_BUCKET_NAME is a globally unique bucket name:

   gcloud storage buckets create gs://BLURRED_BUCKET_NAME

   The Knative serving service uploads blurred images to this bucket. Using a separate bucket prevents processed images from re-triggering the service.

In the following steps, you create and deploy a service that processes notification of file uploads to the INPUT_BUCKET_NAME. You turn on notification delivery after you deploy and test the service, to avoid premature invocation of the new service.

Modifying the Pub/Sub tutorial sample code

This tutorial builds on the code assembled in the Using Pub/Sub tutorial. If you have not yet completed that tutorial, do so now, skipping the cleanup steps, then return here to add image processing behavior.

Adding image processing code

The image processing code is separated from request handling for readability and ease of testing. To add image processing code:

1. Change to the directory of the Pub/Sub tutorial sample code.

2. Add code to import the image processing dependencies, including libraries to integrate with Google Cloud services, ImageMagick, and the file system.

   
   

   Node.js

   Open a new image.js file in your editor, and copy in the following:

   const gm = require('gm').subClass({imageMagick: true});
   const fs = require('fs');
   const {promisify} = require('util');
   const path = require('path');
   const vision = require('@google-cloud/vision');
   
   const {Storage} = require('@google-cloud/storage');
   const storage = new Storage();
   const client = new vision.ImageAnnotatorClient();
   
   const {BLURRED_BUCKET_NAME} = process.env;

   Python

   Open a new image.py file in your editor, and copy in the following:

   import os
   import tempfile
   
   from google.cloud import storage, vision
   from wand.image import Image
   
   storage_client = storage.Client()
   vision_client = vision.ImageAnnotatorClient()

   Go

   Open a new imagemagick/imagemagick.go file in your editor, and copy in the following:

   
   // Package imagemagick contains an example of using ImageMagick to process a
   // file uploaded to Cloud Storage.
   package imagemagick
   
   import (
   	"context"
   	"errors"
   	"fmt"
   	"log"
   	"os"
   	"os/exec"
   
   	"cloud.google.com/go/storage"
   	vision "cloud.google.com/go/vision/apiv1"
   	"cloud.google.com/go/vision/v2/apiv1/visionpb"
   )
   
   // Global API clients used across function invocations.
   var (
   	storageClient *storage.Client
   	visionClient  *vision.ImageAnnotatorClient
   )
   
   func init() {
   	// Declare a separate err variable to avoid shadowing the client variables.
   	var err error
   
   	storageClient, err = storage.NewClient(context.Background())
   	if err != nil {
   		log.Fatalf("storage.NewClient: %v", err)
   	}
   
   	visionClient, err = vision.NewImageAnnotatorClient(context.Background())
   	if err != nil {
   		log.Fatalf("vision.NewAnnotatorClient: %v", err)
   	}
   }
   

   Java

   Open a new src/main/java/com/example/cloudrun/ImageMagick.java file in your editor, and copy in the following:

   import com.google.cloud.storage.Blob;
   import com.google.cloud.storage.BlobId;
   import com.google.cloud.storage.BlobInfo;
   import com.google.cloud.storage.Storage;
   import com.google.cloud.storage.StorageOptions;
   import com.google.cloud.vision.v1.AnnotateImageRequest;
   import com.google.cloud.vision.v1.AnnotateImageResponse;
   import com.google.cloud.vision.v1.BatchAnnotateImagesResponse;
   import com.google.cloud.vision.v1.Feature;
   import com.google.cloud.vision.v1.Feature.Type;
   import com.google.cloud.vision.v1.Image;
   import com.google.cloud.vision.v1.ImageAnnotatorClient;
   import com.google.cloud.vision.v1.ImageSource;
   import com.google.cloud.vision.v1.SafeSearchAnnotation;
   import com.google.gson.JsonObject;
   import java.io.IOException;
   import java.nio.file.Files;
   import java.nio.file.Path;
   import java.nio.file.Paths;
   import java.util.ArrayList;
   import java.util.List;
   
   public class ImageMagick {
   
     private static final String BLURRED_BUCKET_NAME = System.getenv("BLURRED_BUCKET_NAME");
     private static Storage storage = StorageOptions.getDefaultInstance().getService();

3. Add code to receive a Pub/Sub message as an event object and control the image processing.

   The event contains data about the originally uploaded image. This code determines if the image needs to be blurred by checking the results of a Cloud Vision analysis for violent or adult content.

   Node.js

   // Blurs uploaded images that are flagged as Adult or Violence.
   exports.blurOffensiveImages = async event => {
     // This event represents the triggering Cloud Storage object.
     const object = event;
   
     const file = storage.bucket(object.bucket).file(object.name);
     const filePath = `gs://${object.bucket}/${object.name}`;
   
     console.log(`Analyzing ${file.name}.`);
   
     try {
       const [result] = await client.safeSearchDetection(filePath);
       const detections = result.safeSearchAnnotation || {};
   
       if (
         // Levels are defined in https://cloud.google.com/vision/docs/reference/rest/v1/AnnotateImageResponse#likelihood
         detections.adult === 'VERY_LIKELY' ||
         detections.violence === 'VERY_LIKELY'
       ) {
         console.log(`Detected ${file.name} as inappropriate.`);
         return blurImage(file, BLURRED_BUCKET_NAME);
       } else {
         console.log(`Detected ${file.name} as OK.`);
       }
     } catch (err) {
       console.error(`Failed to analyze ${file.name}.`, err);
       throw err;
     }
   };

   Python

   def blur_offensive_images(data):
       """Blurs uploaded images that are flagged as Adult or Violence.
   
       Args:
           data: Pub/Sub message data
       """
       file_data = data
   
       file_name = file_data["name"]
       bucket_name = file_data["bucket"]
   
       blob = storage_client.bucket(bucket_name).get_blob(file_name)
       blob_uri = f"gs://{bucket_name}/{file_name}"
       blob_source = vision.Image(source=vision.ImageSource(image_uri=blob_uri))
   
       # Ignore already-blurred files
       if file_name.startswith("blurred-"):
           print(f"The image {file_name} is already blurred.")
           return
   
       print(f"Analyzing {file_name}.")
   
       result = vision_client.safe_search_detection(image=blob_source)
       detected = result.safe_search_annotation
   
       # Process image
       if detected.adult == 5 or detected.violence == 5:
           print(f"The image {file_name} was detected as inappropriate.")
           return __blur_image(blob)
       else:
           print(f"The image {file_name} was detected as OK.")
   
   

   Go

   
   // GCSEvent is the payload of a GCS event.
   type GCSEvent struct {
   	Bucket string `json:"bucket"`
   	Name   string `json:"name"`
   }
   
   // BlurOffensiveImages blurs offensive images uploaded to GCS.
   func BlurOffensiveImages(ctx context.Context, e GCSEvent) error {
   	outputBucket := os.Getenv("BLURRED_BUCKET_NAME")
   	if outputBucket == "" {
   		return errors.New("BLURRED_BUCKET_NAME must be set")
   	}
   
   	img := vision.NewImageFromURI(fmt.Sprintf("gs://%s/%s", e.Bucket, e.Name))
   
   	resp, err := visionClient.DetectSafeSearch(ctx, img, nil)
   	if err != nil {
   		return fmt.Errorf("AnnotateImage: %w", err)
   	}
   
   	if resp.GetAdult() == visionpb.Likelihood_VERY_LIKELY ||
   		resp.GetViolence() == visionpb.Likelihood_VERY_LIKELY {
   		return blur(ctx, e.Bucket, outputBucket, e.Name)
   	}
   	log.Printf("The image %q was detected as OK.", e.Name)
   	return nil
   }
   

   Java

   // Blurs uploaded images that are flagged as Adult or Violence.
   public static void blurOffensiveImages(JsonObject data) {
     String fileName = data.get("name").getAsString();
     String bucketName = data.get("bucket").getAsString();
     BlobInfo blobInfo = BlobInfo.newBuilder(bucketName, fileName).build();
     // Construct URI to GCS bucket and file.
     String gcsPath = String.format("gs://%s/%s", bucketName, fileName);
     System.out.println(String.format("Analyzing %s", fileName));
   
     // Construct request.
     List<AnnotateImageRequest> requests = new ArrayList<>();
     ImageSource imgSource = ImageSource.newBuilder().setImageUri(gcsPath).build();
     Image img = Image.newBuilder().setSource(imgSource).build();
     Feature feature = Feature.newBuilder().setType(Type.SAFE_SEARCH_DETECTION).build();
     AnnotateImageRequest request =
         AnnotateImageRequest.newBuilder().addFeatures(feature).setImage(img).build();
     requests.add(request);
   
     // Send request to the Vision API.
     try (ImageAnnotatorClient client = ImageAnnotatorClient.create()) {
       BatchAnnotateImagesResponse response = client.batchAnnotateImages(requests);
       List<AnnotateImageResponse> responses = response.getResponsesList();
       for (AnnotateImageResponse res : responses) {
         if (res.hasError()) {
           System.out.println(String.format("Error: %s\n", res.getError().getMessage()));
           return;
         }
         // Get Safe Search Annotations
         SafeSearchAnnotation annotation = res.getSafeSearchAnnotation();
         if (annotation.getAdultValue() == 5 || annotation.getViolenceValue() == 5) {
           System.out.println(String.format("Detected %s as inappropriate.", fileName));
           blur(blobInfo);
         } else {
           System.out.println(String.format("Detected %s as OK.", fileName));
         }
       }
     } catch (Exception e) {
       System.out.println(String.format("Error with Vision API: %s", e.getMessage()));
     }
   }

4. Retrieve the referenced image from the Cloud Storage input bucket created above, use ImageMagick to transform the image with a blur effect, and upload the result to the output bucket.

   Node.js

   // Blurs the given file using ImageMagick, and uploads it to another bucket.
   const blurImage = async (file, blurredBucketName) => {
     const tempLocalPath = `/tmp/${path.parse(file.name).base}`;
   
     // Download file from bucket.
     try {
       await file.download({destination: tempLocalPath});
   
       console.log(`Downloaded ${file.name} to ${tempLocalPath}.`);
     } catch (err) {
       throw new Error(`File download failed: ${err}`);
     }
   
     await new Promise((resolve, reject) => {
       gm(tempLocalPath)
         .blur(0, 16)
         .write(tempLocalPath, (err, stdout) => {
           if (err) {
             console.error('Failed to blur image.', err);
             reject(err);
           } else {
             console.log(`Blurred image: ${file.name}`);
             resolve(stdout);
           }
         });
     });
   
     // Upload result to a different bucket, to avoid re-triggering this function.
     const blurredBucket = storage.bucket(blurredBucketName);
   
     // Upload the Blurred image back into the bucket.
     const gcsPath = `gs://${blurredBucketName}/${file.name}`;
     try {
       await blurredBucket.upload(tempLocalPath, {destination: file.name});
       console.log(`Uploaded blurred image to: ${gcsPath}`);
     } catch (err) {
       throw new Error(`Unable to upload blurred image to ${gcsPath}: ${err}`);
     }
   
     // Delete the temporary file.
     const unlink = promisify(fs.unlink);
     return unlink(tempLocalPath);
   };

   Python

   def __blur_image(current_blob):
       """Blurs the given file using ImageMagick.
   
       Args:
           current_blob: a Cloud Storage blob
       """
       file_name = current_blob.name
       _, temp_local_filename = tempfile.mkstemp()
   
       # Download file from bucket.
       current_blob.download_to_filename(temp_local_filename)
       print(f"Image {file_name} was downloaded to {temp_local_filename}.")
   
       # Blur the image using ImageMagick.
       with Image(filename=temp_local_filename) as image:
           image.resize(*image.size, blur=16, filter="hamming")
           image.save(filename=temp_local_filename)
   
       print(f"Image {file_name} was blurred.")
   
       # Upload result to a second bucket, to avoid re-triggering the function.
       # You could instead re-upload it to the same bucket + tell your function
       # to ignore files marked as blurred (e.g. those with a "blurred" prefix)
       blur_bucket_name = os.getenv("BLURRED_BUCKET_NAME")
       blur_bucket = storage_client.bucket(blur_bucket_name)
       new_blob = blur_bucket.blob(file_name)
       new_blob.upload_from_filename(temp_local_filename)
       print(f"Blurred image uploaded to: gs://{blur_bucket_name}/{file_name}")
   
       # Delete the temporary file.
       os.remove(temp_local_filename)
   
   

   Go

   
   // blur blurs the image stored at gs://inputBucket/name and stores the result in
   // gs://outputBucket/name.
   func blur(ctx context.Context, inputBucket, outputBucket, name string) error {
   	inputBlob := storageClient.Bucket(inputBucket).Object(name)
   	r, err := inputBlob.NewReader(ctx)
   	if err != nil {
   		return fmt.Errorf("NewReader: %w", err)
   	}
   
   	outputBlob := storageClient.Bucket(outputBucket).Object(name)
   	w := outputBlob.NewWriter(ctx)
   	defer w.Close()
   
   	// Use - as input and output to use stdin and stdout.
   	cmd := exec.Command("convert", "-", "-blur", "0x8", "-")
   	cmd.Stdin = r
   	cmd.Stdout = w
   
   	if err := cmd.Run(); err != nil {
   		return fmt.Errorf("cmd.Run: %w", err)
   	}
   
   	log.Printf("Blurred image uploaded to gs://%s/%s", outputBlob.BucketName(), outputBlob.ObjectName())
   
   	return nil
   }
   

   Java

     // Blurs the file described by blobInfo using ImageMagick,
     // and uploads it to the blurred bucket.
     public static void blur(BlobInfo blobInfo) throws IOException {
       String bucketName = blobInfo.getBucket();
       String fileName = blobInfo.getName();
       // Download image
       Blob blob = storage.get(BlobId.of(bucketName, fileName));
       Path download = Paths.get("/tmp/", fileName);
       blob.downloadTo(download);
   
       // Construct the command.
       List<String> args = new ArrayList<>();
       args.add("convert");
       args.add(download.toString());
       args.add("-blur");
       args.add("0x8");
       Path upload = Paths.get("/tmp/", "blurred-" + fileName);
       args.add(upload.toString());
       try {
         ProcessBuilder pb = new ProcessBuilder(args);
         Process process = pb.start();
         process.waitFor();
       } catch (Exception e) {
         System.out.println(String.format("Error: %s", e.getMessage()));
       }
   
       // Upload image to blurred bucket.
       BlobId blurredBlobId = BlobId.of(BLURRED_BUCKET_NAME, fileName);
       BlobInfo blurredBlobInfo =
           BlobInfo.newBuilder(blurredBlobId).setContentType(blob.getContentType()).build();
       try {
         byte[] blurredFile = Files.readAllBytes(upload);
         Blob blurredBlob = storage.create(blurredBlobInfo, blurredFile);
         System.out.println(
             String.format("Blurred image uploaded to: gs://%s/%s", BLURRED_BUCKET_NAME, fileName));
       } catch (Exception e) {
         System.out.println(String.format("Error in upload: %s", e.getMessage()));
       }
   
       // Remove images from fileSystem
       Files.delete(download);
       Files.delete(upload);
     }
   }

Integrating image processing into the Pub/Sub sample code

To modify the existing service to incorporate the image processing code:

1. Add new dependencies for your service, including the Cloud Vision and Cloud Storage client libraries:

   Node.js

   npm install gm @google-cloud/storage @google-cloud/vision

   Python

   Add the necessary client libraries so that your requirements.txt will look something like this:

   Flask==3.0.3
   google-cloud-storage==2.12.0
   google-cloud-vision==3.8.1
   gunicorn==23.0.0
   Wand==0.6.13
   Werkzeug==3.0.3
   

   Go

   The go sample application uses go modules, the new dependencies added above in the imagemagick/imagemagick.go import statement will automatically download by the next command that needs them.

   Java

   Add the following dependency under <dependencyManagement> in the pom.xml:

   <dependency>
     <groupId>com.google.cloud</groupId>
     <artifactId>spring-cloud-gcp-dependencies</artifactId>
     <version>4.9.2</version>
     <type>pom</type>
     <scope>import</scope>
   </dependency>
   

   Add the following dependencies under <dependencies> in the pom.xml:

   <dependency>
     <groupId>com.google.code.gson</groupId>
     <artifactId>gson</artifactId>
     <scope>compile</scope>
   </dependency>
   <dependency>
     <groupId>com.google.cloud</groupId>
     <artifactId>spring-cloud-gcp-starter-vision</artifactId>
   </dependency>
   <dependency>
     <groupId>com.google.cloud</groupId>
     <artifactId>spring-cloud-gcp-starter-storage</artifactId>
   </dependency>
   

2. Add the ImageMagick system package to your container by modifying the Dockerfile below the FROM statement. If using a "multi-stage" Dockerfile, place this in the final stage.

   Debian/Ubuntu

   
   # Install Imagemagick into the container image.
   # For more on system packages review the system packages tutorial.
   # https://cloud.google.com/run/docs/tutorials/system-packages#dockerfile
   RUN set -ex; \
     apt-get -y update; \
     apt-get -y install imagemagick; \
     rm -rf /var/lib/apt/lists/*
   

   Alpine

   
   # Install Imagemagick into the container image.
   # For more on system packages review the system packages tutorial.
   # https://cloud.google.com/run/docs/tutorials/system-packages#dockerfile
   RUN apk add --no-cache imagemagick
   

   Read more about working with system packages in your Knative serving service in the Using system packages tutorial.

3. Replace the existing Pub/Sub message handling code with a function call to our new blurring logic.

   Node.js

   The app.js file defines the Express.js app and prepares received Pub/Sub messages for use. Make the following changes:

   • Add code to import the new image.js file
   • Remove the existing "Hello World" code from the route
   • Add code to further validate the Pub/Sub message

   • Add code to call the new image processing function

     When you are finished, the code will look like this:

   
   const express = require('express');
   const app = express();
   
   // This middleware is available in Express v4.16.0 onwards
   app.use(express.json());
   
   const image = require('./image');
   
   app.post('/', async (req, res) => {
     if (!req.body) {
       const msg = 'no Pub/Sub message received';
       console.error(`error: ${msg}`);
       res.status(400).send(`Bad Request: ${msg}`);
       return;
     }
     if (!req.body.message || !req.body.message.data) {
       const msg = 'invalid Pub/Sub message format';
       console.error(`error: ${msg}`);
       res.status(400).send(`Bad Request: ${msg}`);
       return;
     }
   
     // Decode the Pub/Sub message.
     const pubSubMessage = req.body.message;
     let data;
     try {
       data = Buffer.from(pubSubMessage.data, 'base64').toString().trim();
       data = JSON.parse(data);
     } catch (err) {
       const msg =
         'Invalid Pub/Sub message: data property is not valid base64 encoded JSON';
       console.error(`error: ${msg}: ${err}`);
       res.status(400).send(`Bad Request: ${msg}`);
       return;
     }
   
     // Validate the message is a Cloud Storage event.
     if (!data.name || !data.bucket) {
       const msg =
         'invalid Cloud Storage notification: expected name and bucket properties';
       console.error(`error: ${msg}`);
       res.status(400).send(`Bad Request: ${msg}`);
       return;
     }
   
     try {
       await image.blurOffensiveImages(data);
       res.status(204).send();
     } catch (err) {
       console.error(`error: Blurring image: ${err}`);
       res.status(500).send();
     }
   });

   Python

   The main.py file defines the Flask app and prepares received Pub/Sub messages for use. Make the following changes:

   • Add code to import the new image.py file
   • Remove the existing "Hello World" code from the route
   • Add code to further validate the Pub/Sub message

   • Add code to call the new image processing function

     When you are finished, the code will look like this:

   import base64
   import json
   import os
   
   from flask import Flask, request
   
   import image
   
   
   app = Flask(__name__)
   
   
   @app.route("/", methods=["POST"])
   def index():
       """Receive and parse Pub/Sub messages containing Cloud Storage event data."""
       envelope = request.get_json()
       if not envelope:
           msg = "no Pub/Sub message received"
           print(f"error: {msg}")
           return f"Bad Request: {msg}", 400
   
       if not isinstance(envelope, dict) or "message" not in envelope:
           msg = "invalid Pub/Sub message format"
           print(f"error: {msg}")
           return f"Bad Request: {msg}", 400
   
       # Decode the Pub/Sub message.
       pubsub_message = envelope["message"]
   
       if isinstance(pubsub_message, dict) and "data" in pubsub_message:
           try:
               data = json.loads(base64.b64decode(pubsub_message["data"]).decode())
   
           except Exception as e:
               msg = (
                   "Invalid Pub/Sub message: "
                   "data property is not valid base64 encoded JSON"
               )
               print(f"error: {e}")
               return f"Bad Request: {msg}", 400
   
           # Validate the message is a Cloud Storage event.
           if not data["name"] or not data["bucket"]:
               msg = (
                   "Invalid Cloud Storage notification: "
                   "expected name and bucket properties"
               )
               print(f"error: {msg}")
               return f"Bad Request: {msg}", 400
   
           try:
               image.blur_offensive_images(data)
               return ("", 204)
   
           except Exception as e:
               print(f"error: {e}")
               return ("", 500)
   
       return ("", 500)
   

   Go

   The main.go file defines the HTTP service and prepares received Pub/Sub messages for use. Make the following changes:

   • Add code to import the new imagemagick.go file
   • Remove the existing "Hello World" code from the handler
   • Add code to further validate the Pub/Sub message
   • Add code to call the new image processing function

   
   // Sample image-processing is a Cloud Run service which performs asynchronous processing on images.
   package main
   
   import (
   	"encoding/json"
   	"io"
   	"log"
   	"net/http"
   	"os"
   
   	"github.com/GoogleCloudPlatform/golang-samples/run/image-processing/imagemagick"
   )
   
   func main() {
   	http.HandleFunc("/", HelloPubSub)
   	// Determine port for HTTP service.
   	port := os.Getenv("PORT")
   	if port == "" {
   		port = "8080"
   	}
   	// Start HTTP server.
   	log.Printf("Listening on port %s", port)
   	if err := http.ListenAndServe(":"+port, nil); err != nil {
   		log.Fatal(err)
   	}
   }
   
   // PubSubMessage is the payload of a Pub/Sub event.
   // See the documentation for more details:
   // https://cloud.google.com/pubsub/docs/reference/rest/v1/PubsubMessage
   type PubSubMessage struct {
   	Message struct {
   		Data []byte `json:"data,omitempty"`
   		ID   string `json:"id"`
   	} `json:"message"`
   	Subscription string `json:"subscription"`
   }
   
   // HelloPubSub receives and processes a Pub/Sub push message.
   func HelloPubSub(w http.ResponseWriter, r *http.Request) {
   	var m PubSubMessage
   	body, err := io.ReadAll(r.Body)
   	if err != nil {
   		log.Printf("ioutil.ReadAll: %v", err)
   		http.Error(w, "Bad Request", http.StatusBadRequest)
   		return
   	}
   	if err := json.Unmarshal(body, &m); err != nil {
   		log.Printf("json.Unmarshal: %v", err)
   		http.Error(w, "Bad Request", http.StatusBadRequest)
   		return
   	}
   
   	var e imagemagick.GCSEvent
   	if err := json.Unmarshal(m.Message.Data, &e); err != nil {
   		log.Printf("json.Unmarshal: %v", err)
   		http.Error(w, "Bad Request", http.StatusBadRequest)
   		return
   	}
   
   	if e.Name == "" || e.Bucket == "" {
   		log.Printf("invalid GCSEvent: expected name and bucket")
   		http.Error(w, "Bad Request", http.StatusBadRequest)
   		return
   	}
   
   	if err := imagemagick.BlurOffensiveImages(r.Context(), e); err != nil {
   		log.Printf("imagemagick.BlurOffensiveImages: %v", err)
   		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
   	}
   }
   

   Java

   The PubSubController.java file defines the controller that handles HTTP requests and prepares received Pub/Sub messages for use. Make the following changes:

   • Add the new imports
   • Remove the existing "Hello World" code from the controller
   • Add code to further validate the Pub/Sub message
   • Add code to call the new image processing function

   import com.google.gson.JsonObject;
   import com.google.gson.JsonParser;
   import java.util.Base64;
   import org.springframework.http.HttpStatus;
   import org.springframework.http.ResponseEntity;
   import org.springframework.web.bind.annotation.RequestBody;
   import org.springframework.web.bind.annotation.RequestMapping;
   import org.springframework.web.bind.annotation.RequestMethod;
   import org.springframework.web.bind.annotation.RestController;
   
   // PubsubController consumes a Pub/Sub message.
   @RestController
   public class PubSubController {
     @RequestMapping(value = "/", method = RequestMethod.POST)
     public ResponseEntity<String> receiveMessage(@RequestBody Body body) {
       // Get PubSub message from request body.
       Body.Message message = body.getMessage();
       if (message == null) {
         String msg = "Bad Request: invalid Pub/Sub message format";
         System.out.println(msg);
         return new ResponseEntity<>(msg, HttpStatus.BAD_REQUEST);
       }
   
       // Decode the Pub/Sub message.
       String pubSubMessage = message.getData();
       JsonObject data;
       try {
         String decodedMessage = new String(Base64.getDecoder().decode(pubSubMessage));
         data = JsonParser.parseString(decodedMessage).getAsJsonObject();
       } catch (Exception e) {
         String msg = "Error: Invalid Pub/Sub message: data property is not valid base64 encoded JSON";
         System.out.println(msg);
         return new ResponseEntity<>(msg, HttpStatus.BAD_REQUEST);
       }
   
       // Validate the message is a Cloud Storage event.
       if (data.get("name") == null || data.get("bucket") == null) {
         String msg = "Error: Invalid Cloud Storage notification: expected name and bucket properties";
         System.out.println(msg);
         return new ResponseEntity<>(msg, HttpStatus.BAD_REQUEST);
       }
   
       try {
         ImageMagick.blurOffensiveImages(data);
       } catch (Exception e) {
         String msg = String.format("Error: Blurring image: %s", e.getMessage());
         System.out.println(msg);
         return new ResponseEntity<>(msg, HttpStatus.INTERNAL_SERVER_ERROR);
       }
       return new ResponseEntity<>(HttpStatus.OK);
     }
   }

Downloading the complete sample

To retrieve the complete Image Processing code sample for use:

1. Clone the sample app repository to your local machine:

   Node.js

   git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git

   Alternatively, you can download the sample as a zip file and extract it.

   Python

   git clone https://github.com/GoogleCloudPlatform/python-docs-samples.git

   Alternatively, you can download the sample as a zip file and extract it.

   Go

   git clone https://github.com/GoogleCloudPlatform/golang-samples.git

   Alternatively, you can download the sample as a zip file and extract it.

   Java

   git clone https://github.com/GoogleCloudPlatform/java-docs-samples.git

   Alternatively, you can download the sample as a zip file and extract it.

2. Change to the directory that contains the Knative serving sample code:

   Node.js

   cd nodejs-docs-samples/run/image-processing/

   Python

   cd python-docs-samples/run/image-processing/

   Go

   cd golang-samples/run/image-processing/

   Java

   cd java-docs-samples/run/image-processing/

Shipping the code

Shipping code consists of three steps: building a container image with Cloud Build, uploading the container image to Container Registry, and deploying the container image to Knative serving.

To ship your code:

1. Build your container and publish on Container Registry:

   Node.js

   gcloud builds submit --tag gcr.io/PROJECT_ID/pubsub

   Where PROJECT_ID is your Google Cloud project ID, and pubsub is the name you want to give your service.

   Upon success, you will see a SUCCESS message containing the ID, creation time, and image name. The image is stored in Container Registry and can be re-used if desired.

   Python

   gcloud builds submit --tag gcr.io/PROJECT_ID/pubsub

   Where PROJECT_ID is your Google Cloud project ID, and pubsub is the name you want to give your service.

   Upon success, you will see a SUCCESS message containing the ID, creation time, and image name. The image is stored in Container Registry and can be re-used if desired.

   Go

   gcloud builds submit --tag gcr.io/PROJECT_ID/pubsub

   Where PROJECT_ID is your Google Cloud project ID, and pubsub is the name you want to give your service.

   Upon success, you will see a SUCCESS message containing the ID, creation time, and image name. The image is stored in Container Registry and can be re-used if desired.

   Java

   This sample uses Jib to build Docker images using common Java tools. Jib optimizes container builds without the need for a Dockerfile or having Docker installed. Learn more about building Java containers with Jib.

   1. Using the Dockerfile, configure and build a base image with the system packages installed to override Jib's default base image:

      # Use eclipse-temurin for base image.
      # It's important to use JDK 8u191 or above that has container support enabled.
      # https://hub.docker.com/_/eclipse-temurin/
      # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
      FROM eclipse-temurin:17.0.16_8-jre
      
      # Install Imagemagick into the container image.
      # For more on system packages review the system packages tutorial.
      # https://cloud.google.com/run/docs/tutorials/system-packages#dockerfile
      RUN set -ex; \
        apt-get -y update; \
        apt-get -y install imagemagick; \
        rm -rf /var/lib/apt/lists/*

      gcloud builds submit --tag gcr.io/PROJECT_ID/imagemagick

      Where PROJECT_ID is your Google Cloud project ID.

   2. Build your final container with Jib and publish on Container Registry:

      <plugin>
        <groupId>com.google.cloud.tools</groupId>
        <artifactId>jib-maven-plugin</artifactId>
        <version>3.4.0</version>
        <configuration>
          <from>
            <image>gcr.io/PROJECT_ID/imagemagick</image>
          </from>
          <to>
            <image>gcr.io/PROJECT_ID/pubsub</image>
          </to>
        </configuration>
      </plugin>
      

      mvn compile jib:build \
        -Dimage=gcr.io/PROJECT_ID/pubsub \
        -Djib.from.image=gcr.io/PROJECT_ID/imagemagick

      Where PROJECT_ID is your Google Cloud project ID.

2. Run the following command to deploy your service, using the same service name you used in the Pub/Sub tutorial:

   Node.js

   gcloud run deploy pubsub-tutorial --image gcr.io/PROJECT_ID/pubsub --set-env-vars=BLURRED_BUCKET_NAME=BLURRED_BUCKET_NAME

   Python

   gcloud run deploy pubsub-tutorial --image gcr.io/PROJECT_ID/pubsub --set-env-vars=BLURRED_BUCKET_NAME=BLURRED_BUCKET_NAME

   Go

   gcloud run deploy pubsub-tutorial --image gcr.io/PROJECT_ID/pubsub --set-env-vars=BLURRED_BUCKET_NAME=BLURRED_BUCKET_NAME

   Java

   gcloud run deploy pubsub-tutorial --image gcr.io/PROJECT_ID/pubsub --set-env-vars=BLURRED_BUCKET_NAME=BLURRED_BUCKET_NAME --memory 512M

   Replace PROJECT_ID with your Google Cloud project ID. pubsub is the container name and pubsub-tutorial is the name of the service. Notice that the container image is deployed to the service and cluster that you configured previously under Setting up gcloud defaults.

   Replace BLURRED_BUCKET_NAME with your Cloud Storage bucket you created earlier to receive blurred images to set the environment variable.

   Wait until the deployment is complete: this can take about half a minute. On success, the command line displays the service URL.

Turning on notifications from Cloud Storage

Configure Cloud Storage to publish a message to a Pub/Sub topic whenever a file (known as an object), is uploaded or changed. Send the notification to the previously created topic so any new file upload will invoke the service.

gcloud storage buckets notifications create gs://INPUT_BUCKET_NAME --topic=myRunTopic --payload-format=json

This command is installed as part of the Google Cloud CLI. myRunTopic is the topic you created in the previous tutorial.

Replace INPUT_BUCKET_NAME with the name you used when you created the buckets.

For more details about storage bucket notifications, read object change notifications.

Trying it out

1. Upload an offensive image, such as this image of a flesh-eating zombie:

   gcloud storage cp zombie.jpg gs://INPUT_BUCKET_NAME

   where INPUT_BUCKET_NAME is the Cloud Storage bucket you created earlier for uploading images.

2. Navigate to the service logs:

   1. Navigate to the Knative serving page in the Google Cloud console:

      Go to Knative serving

   2. Click the pubsub-tutorial service.

   3. Select the Logs tab. Logs might take a few moments to appear. If you don't see them immediately, check again after a few moments.

3. Look for the Blurred image: zombie.png message.

4. You can view the blurred images in the BLURRED_BUCKET_NAME Cloud Storage bucket you created earlier: locate the bucket in the Cloud Storage page in the Google Cloud console