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Unit 3

Creating Graphics & Images Bit by Bit

3.1 Unit Overview

3.2 Paint Pot Tutorial

3.3 Representing Images

3.4 Paint Pot Projects

3.5 Paint Pot Refactoring

3.6 Error Detection

3.7 Parity Error Checking

3.8 Magic 8 Ball

3.9 Persisting Photos

3.10 Map Tour

3.11BB Electronic Documents

3.12 Wrap Up


Computer Science Graphics

This unit focuses on App Inventor's drawing and painting features and related topics from the CS Principles curriculum.

Unit Features

Programming: The programming in this unit focuses mainly on App Inventor's graphics features. The Paint Pot app, the App Inventor version of the classic finger painting program, is presented in three parts. A basic Paint Pot tutorial introduces App Inventor's Canvas component and some of its drawing and painting commands as well as introduces the concept of a global variable and the programming technique of incrementing a variable. This tutorial is also followed by creative exercises. Later in the unit, images will be used with the Canvas and saved using persistent data.

There are two other programming tutorials, the Magic 8 Ball app provides a first introduction to lists, an important data structure found in most programming languages. And, finally, the Map Tour, an optional app, introduces a technique for accessing other apps from within App Inventor. In this example, we learn how to access and control Google Maps from within a mobile app.

CS Principles: The CS Principles lessons in this unit will extend our understanding of the binary system. In one lesson we learn how digital images are represented in binary. In another, we learn how binary numbers can be used to help with error detection during data transmission. These lessons are complemented nicely by a Blown to Bits reading that focuses on digital documents, including how they can be used to hide secrets.

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