In this lesson, you will create a Scratch project that uses a Google Teachable Machine Image model to recognize rock, paper, and scissors hand gestures.

First, go to stretch3.github.io to create a new Scratch project.

Stretch3 is an experimental version of Scratch 3 that allows you to use additional extensions like TM2Scratch, which we will need for using our AI image model.

Now, let's add the TM2Scratch extension to your project.

Click on the 'Extensions' button at the bottom-left corner of the screen, and then click on 'TM2Scratch'. This extension allows you to use Google Teachable Machine Image models in your Scratch projects.

When you add this extension, it will automatically try and use your computer's camera. If necessary, click on 'Allow' to give it permission to use your camera. You should see what the camera is showing in the stage area.

Scratch: How to add extension blocks

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Understanding and Adding Extensions in Scratch

What are Scratch Extensions?

Scratch Extensions are additional sets of blocks that expand the capabilities of your Scratch projects. They allow you to:

1. Mention extensions like Pen here
2. Connect with external hardware (e.g., microbits)
3. Access web-based services (e.g., Google Translate, Amazon Text to Speech)
4. Use more advanced programming features

How Extensions Work

When you add an extension to your project:

• New blocks appear in the blocks palette
• These blocks are grouped under a category named after the extension
• You can use these blocks just like any other Scratch blocks

Adding an Extension to Your Project

1. Look for the "Add Extension" button in the bottom-left corner of the Scratch editor
2. Click the "Add Extension" button
3. A window will open showing all available extensions
4. Browse through the options or use the search bar to find a specific extension
5. Click on the extension you want to add
6. The extension is now added to your project, and its blocks appear in the blocks palette

Now, let's set up the image model that our project will use. Add the following code to the Cat sprite:

Put the link of your image model into the image classification model URL block.

Here's what the code does:

• turn video [on v]: This block turns on the video from your webcam or computer camera.
• Label once every (1 v) seconds: This block tells the program to recognize the hand gesture every second.
• image classification model URL [link to your model]: This block sets the URL of the image model that will be used to recognize the hand gestures.

Click on the 'image label' block in the TM2Scratch extension category to turn it on. This will show you the current image label being applied to what's being recorded on your webcam.