Rainbow — Accessibility Contrast Tool for Text on Images

The project creates a website which can be used as a tool for keep text legible when overlayed on images. It is easy to forget low contrast between text and background image can make text difficult to read. This is especially true for partially sighted people.

Typically to keep the text legible, designers place an overlay over the image. For example, for an image with with text, a blacl overlay with low transparency (alpha) darkens the image so there is enough contrast between light areas of the image and the white text.

This tool will work out the minimum alpha needed to get a contrast ratio of 4.5 between the text and the lightest pixel in the image. You don't have to stick with white text, or a black overlay. You can even increase the target contrast ratio, if that's what you want. The calculations are run using serverless Rust code, so the UX remains responsive while the numbers are crunching.

Features:

• Site use Gatsby v3 for speed
• Serverless code written in Rust for speed
• Axe clean site — site has been optimisd for accessility using deque axe tools

🚀 Quick start

1. Create a Gatsby 3 site.

   Use the Gatsby 3 CLI to create a new site, specifying the hello-world starter.

   # create a new Gatsby 3 MDX blog site using gatsby-starter-climate
   gatsby new my-mdx-blog-starter https://github.com/rodneylab/gatsby-starter-climate

2. Start developing.

   Navigate into your new site’s directory, copy the example environment variables (and customise them to suit your needs) and start it up.

   cd my-mdx-blog-starter/
   cp .env.EXAMPLE .env.development
   cp .env.EXAMPLE .env.production
   gatsby develop

3. Open the source code and start editing!

   Your site is now running at http://localhost:8000!

   Note: You'll also see a second link: http://localhost:8000/___graphql. This is a tool you can use to experiment with querying your data. Learn more about using this tool in the Gatsby 3 tutorial.

   Open the my-mdx-blog-starter directory in your code editor of choice and edit src/pages/index.jsx. Save your changes and the browser will update in real time!

🧐 What's inside?

A quick look at the top-level files and directories you'll see in a Gatsby 3 project.

.
├── cypress
├── node_modules
├── src
├── .env.EXAMPLE
├── .eslintrc.js
├── .gitignore
├── .prettierrc
├── commitlint.config.js
├── csp-util
├── gatsby-browser.js
├── gatsby-config.js
├── gatsby-node.js
├── gatsby-ssr.js
├── LICENSE
├── netlify.toml
├── package-lock.json
├── package.json
└── README.md

1. /cypress: This directory contains Cypress axe accessibility end-to-end tests. You can expand the tests to suit your needs.

2. /node_modules: This directory contains all of the modules of code that your project depends on (npm packages) are automatically installed.

3. /src: This directory will contain all of the code related to what you will see on the front-end of your site (what you see in the browser) such as your site header or a page template. src is a convention for “source code”.

4. .env.EXAMPLE: This file contains example environment variables. Make two copies to this same root folder: .env.development and .env.production and add your personal environment variables. These two files will be excluded from git commits by default.

5. .eslintrc.js: This file tells ESLint which linting rules to apply. Set to use Airbnb rules by default. Adjust to suit your taste. As well as code style rules, it applies a11y recommended accessibility checks.

6. .gitignore: This file tells git which files it should not track / not maintain a version history for.

7. .prettierrc: This is a configuration file for Prettier. Prettier is a tool to help keep the formatting of your code consistent.

8. .stylelintrc.json: This is a configuration file for StyleLint. Stylelint is a tool to help keep the formatting of your code consistent. It can be used in teams to enforce a consistent coding style.

9. commitlint.config.js: Configuration for commitlint which is used to enforce conventional git commits. This works in tandem with husky configuration in the package.json file.

10. csp-util: This is a script for placing CSP hashes in Netlify headers, improving site security when running on Netlify.

11. gatsby-browser.js: This file is where Gatsby 3 expects to find any usage of the Gatsby 3 browser APIs (if any). These allow customisation/extension of default Gatsby settings affecting the browser.

12. gatsby-config.js: This is the main configuration file for a Gatsby 3 site. This is where you can specify information about your site (metadata) like the site title and description, which Gatsby 3 plugins you’d like to include, etc. (Check out the config docs for more detail). To improve security, fairly strict security header parameters are set. You will almost certainly need to tweak these for your own use case. For help use the following resources:

    • securityheaders.com
    • csper.io
    • csp-evaluator.withgoogle.com

13. gatsby-node.js: This file is where Gatsby 3 expects to find any usage of the Gatsby 3 Node APIs (if any). These allow customisation/extension of default Gatsby 3 settings affecting pieces of the site build process.

14. gatsby-ssr.js: This file is where Gatsby 3 expects to find any usage of the Gatsby 3 server-side rendering APIs (if any). These allow customisation of default Gatsby 3 settings affecting server-side rendering.

15. LICENSE: This Gatsby 3 starter is licensed under the BSD-3-Clause license.

16. netlify.toml This file contains configuration for Netlify builds. It includes an instruction to use the Netlify netlify-plugin-gatsby-cache plugin which helps improve build speed on Netlify. It also includes the custom build command, defined in package.json, which generates Netlify headers with CSP hashes.

17. package-lock.json (See package.json below, first). This is an automatically generated file based on the exact versions of your npm dependencies that were installed for your project. (You won’t change this file directly).

18. package.json: A manifest file for Node.js projects, which includes things like metadata (the project’s name, author, etc). This manifest is how npm knows which packages to install for your project.

19. README.md: A text file containing useful reference information about your project.

💫 Deploy

Build, Deploy, and Host On Netlify

Netlify offers an easy to configure environment and a generous free tier. With baked-in CDN and automated TLS certificates it is a great choice for getting your Gatsby 3 MDX blog up and running at warp speed.

Run the custom build script to ensure CSP hashes are generated and added to Netlify headers:

npm run build

Netlify CMS can run in any frontend web environment, but the quickest way to try it out is by running it on a pre-configured starter site with Netlify. Use the button below to build and deploy your own copy of the repository:

After clicking that button, you’ll authenticate with GitHub and choose a repository name. Netlify will then automatically create a repository in your GitHub account with a copy of the files from the template. Next, it will build and deploy the new site on Netlify, bringing you to the site dashboard when the build is complete. Next, you’ll need to set up Netlify’s Identity service to authorise users to log in to the CMS.