CoderCards - Class Libary Version

This is a precompiled function version of the Azure Functions sample CoderCards.

About the sample

• This sample uses the new precompiled function feature. The project is a regular ASP.NET Web Application project. With a few tweaks, you can run and debug the project locally using the Azure Functions CLI. (See intructions below.)

• The function is triggered when a new .jpg file appears in the container in the app setting/environment variable input-container. See function.json.

• Based on an input image, one of 4 card templates is chosen based on emotion

• The filename of the input image is used to draw the name and title on the card.

• In order for the name and title to be drawn, the filename must be in the form Name of person-Title of person.jpg

• A score based on the predominant emotion (e.g., anger, happiness) is drawn on the top

• The card is written to the output blob container specified by the app setting output-container. See function.json.

Required App Settings

Key	Description
AzureWebJobsStorage	Storage account connection string
EmotionAPIKey	Key for Cognitive Services Emotion API
input-container	Name of Storage container for input images. Use a value like "local-card-input" locally and "card-input" on Azure
input-container	Name of Storage container for output images. Use a value like "local-card-output" locally and "card-output" on Azure
HOME	Set to "." when running locally. Is automatically set on Azure
SITE_PATH	Use "." when running locally. Use site\\wwwroot on Azure

Local debugging in Visual Studio

Since the project is a Web App, by default F5 will launch IIS Express. With a few simple changes to the project settings, you can run the Azure Functions CLI and attach a debugger:

• Right-click CoderCardsWebsite and open Properties.

• In the Web tab, choose Start External Program

• For the program path, enter the path to func.exe for the Azure Functions CLI.

  • If you've installed the Visual Studio Tools for Azure Functions, the path will look something like C:\Users\USERNAME\AppData\Local\Azure.Functions.Cli\1.0.0-beta.91\func.exe
  • If you've installed the Azure Functions CLI through NPM, the path will be something like C:\Users\USERNAME\AppData\Roaming\npm\node_modules\azure-functions-cli\bin\func.exe

• For Command line arguments set host start

• For Working directory, specify the root of the project CoderCardsWebsite on your machine.

Running the demo

1. Choose images that are square with a filename in the form Name of person-Title of person.jpg. The filename is parsed to produce text on the card.

2. Drop images into the card-input container. Once the function runs, you'll see generated cards in card-output.

Notes

• The demo uses System.Drawing, which is NOT recommended for production apps. To learn more, see Why you should not use System.Drawing from ASP.NET applications.

• Happy faces get a multiplier of 4, angry gets a multiplier of 2. I encourage you to tweak for maximum comedic effect!

Talking points about Azure Functions

• The code is triggered off a new blob in a container. We automatically get a binding for both the byte array and the blob name

• The blob name is used to generate the text on the image

• The input binding is just a byte array, which makes it easy to manipulate with memory streams (no need to create new ones)

• Other binding types for C# are Stream, CloudBlockBlob, etc, which is very flexible.

• The output binding is just a stream that you just write to

• This is a very declarative model, details of binding are in a separate json file that can be edited manually or through the Integrate UX

• In general, functions will scale based on the amount of events in input. A real system would probably use something like Azure Queue or Service Bus triggers, in order to track messages more closely.