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

We want to see way more pixels on our page. There's no way anyone wants to sit and buy each individual pixel. Instead, what we're going to do is write a script, that will take an image and a location as input, and then submit the necessary transactions to geth to color those pixels.

Before we can do that, though, we need to write a script that will read an image. We're going to use the 

// Usage: node scripts/buy-pixels.js resourhelmet-mario-running.gif 700 450
// First we'll requite get-pixels
const getPixels = require('get-pixels');

// Next we process the commandline arguments.
// For a real commandline tool I'd use something like yargs, but we'll just use process.argv for now.
// The arguments will be the imagePath, the x position and the y position.
let imagePath = process.argv[2];
let xPos = parseInt(process.argv[3]);
let yPos = parseInt(process.argv[4]);
console.log(imagePath, xPos, yPos);

---
title: Buying An Image -- Reading Pixels


slug: 'buying-an-image-reading-pixels'
thumbnail: https://embed-ssl.wistia.com/deliveries/3393acae9bdf898d762638c14467c7cb5e3e422d.jpg

privateVideoUrl: https://fullstack.wistia.com/medias/6pp9igjpnb



---

We want to see way more pixels on our page. There's no way anyone wants to sit and buy each individual pixel. Instead, what we're going to do is write a script, that will take an image and a location as input, and then submit the necessary transactions to geth to color those pixels.

Before we can do that, though, we need to write a script that will read an image. We're going to use the `get-pixels` library to read images.

First, let's create a `scripts` folder to save this utility script.

> The rest of the script can be found in `scripts/buy-pixels-001-read.js` below

```javascript
// Usage: node scripts/buy-pixels.js resourhelmet-mario-running.gif 700 450
// First we'll requite get-pixels
const getPixels = require('get-pixels');

// Next we process the commandline arguments.
// For a real commandline tool I'd use something like yargs, but we'll just use process.argv for now.
// The arguments will be the imagePath, the x position and the y position.
let imagePath = process.argv[2];
let xPos = parseInt(process.argv[3]);
let yPos = parseInt(process.argv[4]);
console.log(imagePath, xPos, yPos);

The rest of the script can be found in `scripts/buy-pixels-001-read.js` below

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

Buying An Image -- Reading Pixels