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Using Gatsby Image to Prevent Image Bloat

gatsby-image is a React component designed to work seamlessly with Gatsby’s GraphQL queries (gatsby-image plugin README). It combines Gatsby’s native image processing capabilities with advanced image loading techniques to easily and completely optimize image loading for your sites. gatsby-image uses gatsby-plugin-sharp to power its image transformations.

Warning: gatsby-image is not a drop-in replacement for <img />. It’s optimized for fixed width/height images and images that stretch the full-width of a container. Some ways you can use <img /> won’t work with gatsby-image.

Demo

gatsby-image includes the tricks you’d expect from a modern image component. It:

  • uses the new IntersectionObserver API to cheaply lazy load images
  • holds an image’s position so your page doesn’t jump around as images load
  • makes it easy to add a placeholder—either a gray background or a blurry version of the image.

For more complete API information, check out the Gatsby Image API docs.

Problem

Large, unoptimized images dramatically slow down your site.

But creating optimized images for websites has long been a thorny problem. Ideally you would:

  • Resize large images to the size needed by your design
  • Generate multiple smaller images so smartphones and tablets don’t download desktop-sized images
  • Strip all unnecessary metadata and optimize JPEG and PNG compression
  • Efficiently lazy load images to speed initial page load and save bandwidth
  • Use the “blur-up” technique or a “traced placeholder” SVG to show a preview of the image while it loads
  • Hold the image position so your page doesn’t jump while images load

Doing this consistently across a site feels like sisyphean labor. You manually optimize your images and then… several images are swapped in at the last minute or a design-tweak shaves 100px of width off your images.

Most solutions involve a lot of manual labor and bookkeeping to ensure every image is optimized.

This isn’t ideal. Optimized images should be easy and the default.

Solution

With Gatsby, we can make the experience of working with images way, way better.

gatsby-image is designed to work seamlessly with Gatsby’s native image processing capabilities powered by GraphQL and Sharp. To produce perfect images with minimal effort, you can:

  1. Install gatsby-image and other, necessary dependencies like gatsby-plugin-sharp and gatsby-transformer-sharp
npm install --save gatsby-image gatsby-transformer-sharp gatsby-plugin-sharp
  1. Add the newly installed plugins and transformer plugins to your gatsby-config.js
gatsby-config.js
module.exports = {
plugins: [`gatsby-plugin-sharp`, `gatsby-transformer-sharp`],
}
  1. Configure gatsby-source-filesystem to load images from a folder. In order to use GraphQL to query the image files, the files need to be in a location that is known to Gatsby. This requires an update to gatsby-config.js to configure the plugin. Feel free to replace the path option to reference wherever your images are located in your project.
gatsby-config.js
module.exports = {
plugins: [
`gatsby-transformer-sharp`,
`gatsby-plugin-sharp`,
{
resolve: `gatsby-source-filesystem`,
options: {
path: `${__dirname}/src/data/`,
},
},
],
}
  1. Write a GraphQL query using one of the included GraphQL “fragments” which specify the fields needed by gatsby-image to create a responsive, optimized image. This example queries for an image at a path relative to the location specified in the gatsby-source-filesystem options using the GatsbyImageSharpFluid fragment.
file(relativePath: { eq: "images/default.jpg" }) {
childImageSharp {
# Specify the image processing specifications right in the query.
fluid {
...GatsbyImageSharpFluid
}
}
}
  1. Import Img to display the fragment in JSX. There are additional features available with the Img tag as well, such as the alt attribute for accessibility.
import Img from "gatsby-image"
export default ({ data }) => (
<div>
<h1>Hello gatsby-image</h1>
<Img
fluid={data.file.childImageSharp.fluid}
alt="Gatsby Docs are awesome"
/>
</div>
)

This GraphQL query creates multiple sizes of the image and when the page is rendered the image that is appropriate for the current screen resolution (e.g. desktop, mobile, and everything in between) is used. The gatsby-image component automatically enables a blur-up effect as well as lazy loading images that are not currently on screen.

So this is all very nice and it’s far better to be able to use this from npm vs. implementing it yourself or cobbling together several standalone libraries.

Additional resources


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