Million Ether Homepage

Storing Colors in a Pixel Grid

Million Ether Page Essential Smart Contract

Tip: Mining only when there are transactions

Tip: Using Remix IDE

Getting Started

Getting The Pixels and Ethereum Events

Building a DApp UI

Drawing in HTML Canvas

Using Websockets with Web3

Web3 and Events Over WebSockets

Drawing Pixels from the Blockchain

Viewing Pixels

Buying An Image -- Reading Pixels

Buying An Image -- Sending Transactions

Pixel bidding and structs

Payable Contracts, payable Functions

Contract Owner and require

Payable color pixel function

Buying Pixels

Sending funds from a contract

The safer way to send funds from a contract

The Pull Payment Pattern - Withdraw payments when outbid

Million Ether Homepage Summary

Auctioning Pixels

solidity

In this course, we'll build a DApp inspired by [The Million Dollar Homepage](https://en.wikipedia.org/wiki/The_Million_Dollar_Homepage). We'll build a 1 million pixel page, and each pixel can be colored by placing the highest bid.

In this course we'll walk through every step of writing a smart contract, deploying it, hosting auctions, and connecting it to the browser through web3. 

If you're looking to build real, full-stack ethereum Dapps, then this is a perfectly-sized example.

We'll build a DApp inspired by the Million Dollar Homepage, powered by an auction on the Ethereum blockchain

To draw our pixels on a page, we first need to understand how to draw pixels on a canvas. In this video, we're going to quickly cover the HTML canvas API and show how we can use it to draw colors.  

<h1>Million Ether Page</h1>
<div class="canvasContainer">
  <canvas id="canvas" width="1000" height="1000"></canvas
</div>

In our canvas tag, we specify a width and height in the number of pixels that we want to show.

In src/index.js, the first thing we want to do is create a 

We'll call this function when the body has loaded.

function draw() {
  // ...
}

document.body.onload = function() {
  draw();
};

 element from the page and start working with it. There are a few layers of APIs we need to go through to get to what we want. But what we're about to do is get the pixel data from the canvas, and write new pixels onto it.

The API can be a little involved at first, but I'll walk through each step, and you can check out the canvas API documentation if you want to learn more about the details.

. The arguments mean we want to start at the first pixel 

---
title: Drawing in HTML Canvas 


slug: 'drawing-in-html-canvas'
thumbnail: https://embed-ssl.wistia.com/deliveries/1ded84bbfba10b3ffa2bb4205574da4ccd2c4bef.jpg

privateVideoUrl: https://fullstack.wistia.com/medias/hlm0pwnl76



---

To draw our pixels on a page, we first need to understand how to draw pixels on a canvas. In this video, we're going to quickly cover the HTML canvas API and show how we can use it to draw colors.  

The first thing we need to do, is add a `canvas` tag to our HTML page:

```html

<h1>Million Ether Page</h1>
<div class="canvasContainer">
  <canvas id="canvas" width="1000" height="1000"></canvas
</div>
```

In our canvas tag, we specify a width and height in the number of pixels that we want to show.

In src/index.js, the first thing we want to do is create a `draw()` function. 

We'll call this function when the body has loaded.

```javascript
function draw() {
  // ...
}

document.body.onload = function() {
  draw();
};
```

Next, we need to fetch the `canvas` element from the page and start working with it. There are a few layers of APIs we need to go through to get to what we want. But what we're about to do is get the pixel data from the canvas, and write new pixels onto it.

The API can be a little involved at first, but I'll walk through each step, and you can check out the canvas API documentation if you want to learn more about the details.

From our `canvas`, we get what's called a _drawing context_. In this case, we want a `2d` context, which lets us draw pixels. 

Next, we read the _image data_ from the drawing context by using `getImageData`. The arguments mean we want to start at the first pixel `(0,0)` and capture the entire image, up to `(canvas.width,canvas.height)`.

Learn

The newline Guide to Building Your First GraphQL Server with Node and TypeScript

Teach

Amelia Wattenberger

Author of Fullstack D3

Community

Million Ether Homepage

WELCOMEIntroduction

Introduction:

Start Here

Module 1: Getting Started

Lesson 1: (3:23)

Million Ether Homepage

Lesson 2: (3:18)

Storing Colors in a Pixel Grid

Lesson 3: (4:29)

Million Ether Page Essential Smart Contract

Lesson 4: (1:56)

Tip: Mining only when there are transactions

Lesson 5: (7:08)

Tip: Using Remix IDE

Module 2: Viewing Pixels

Lesson 1: (6:08)

Getting The Pixels and Ethereum Events

Lesson 2: (7:15)

Gas

Lesson 3: (1:01)

Building a DApp UI

Lesson 4: (3:09)

Drawing in HTML Canvas

Lesson 5: (1:15)

Using Websockets with Web3

Lesson 6: (3:09)

Web3 and Events Over WebSockets

Lesson 7: (3:41)

Drawing Pixels from the Blockchain

Module 3: Buying Pixels

Lesson 1: (1:57)

Buying An Image -- Reading Pixels

Lesson 2: (4:51)

Buying An Image -- Sending Transactions

Lesson 3: (1:25)

Pixel bidding and structs

Lesson 4: (2:48)

Payable Contracts, payable Functions

Lesson 5: (3:35)

Contract Owner and require

Lesson 6: (2:38)

Payable color pixel function

Module 4: Auctioning Pixels

Lesson 1: (4:03)

Sending funds from a contract

Lesson 2: (3:26)

The safer way to send funds from a contract

Lesson 3: (4:37)

The Pull Payment Pattern - Withdraw payments when outbid

Lesson 4: (6:46)

Million Ether Homepage Summary

Drawing in HTML Canvas