Using Gatsby Image to Prevent Image Bloat

This doc is for the deprecated gatsby-image package. See Using the Gatsby Image plugin for the new image plugin.

Using images in Gatsby components and pages requires four steps to take advantage of performance benefits.

shell

npm install gatsby-transformer-sharp gatsby-plugin-sharp gatsby-image gatsby-source-filesystem

Using images in Gatsby requires a few different plugins.

Install gatsby-transformer-sharp and gatsby-plugin-sharp to transform and process your images. gatsby-image is a package that includes a component you’ll use later in “View”.

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.

Here’s a demo site that uses the gatsby-image plugin

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 possible 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 the images load

Doing this consistently across a site feels like a task that can never be completed. 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, you 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:

Install gatsby-image and other, necessary dependencies like gatsby-plugin-sharp and gatsby-transformer-sharp

Add the newly installed plugins and transformer plugins to your gatsby-config.js

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.

Video hosted on egghead.io.

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.

Video hosted on egghead.io.

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.

Video hosted on egghead.io.

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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