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gatsby-image

Speedy, optimized images without the work.

gatsby-image is a React component specially designed to work seamlessly with Gatsby’s GraphQL queries. 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

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 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, you need only:

  1. Import gatsby-image and use it in place of the built-in img
  2. Write a GraphQL query using one of the included GraphQL “fragments” which specify the fields needed by gatsby-image.

The GraphQL query creates multiple thumbnails with optimized JPEG and PNG compression. The gatsby-image component automatically sets up the “blur-up” effect as well as lazy loading of images further down the screen.

Install

npm install --save gatsby-image

Depending on the gatsby starter you used, you may need to include gatsby-transformer-sharp and gatsby-plugin-sharp as well, and make sure they are installed and included in your gatsby-config.

npm install --save gatsby-transformer-sharp
npm install --save gatsby-plugin-sharp

Then in your gatsby-config.js:

plugins: [
  `gatsby-transformer-sharp`,
  `gatsby-plugin-sharp`
];

How to use

This is what a component using gatsby-image looks like:

import React from "react";
import Img from "gatsby-image";

export default ({ data }) => (
  <div>
    <h1>Hello gatsby-image</h1>
    <Img resolutions={data.file.childImageSharp.resolutions} />
  </div>
);

export const query = graphql`
  query GatsbyImageSampleQuery {
    file(relativePath: { eq: "blog/avatars/kyle-mathews.jpeg" }) {
      childImageSharp {
        # Specify the image processing specifications right in the query.
        # Makes it trivial to update as your page's design changes.
        resolutions(width: 125, height: 125) {
          ...GatsbyImageSharpResolutions
        }
      }
    }
  }
`;

For another explanation of how to get started with gatsby-image, see this blog post by community member Kyle Gill Image Optimization Made Easy with Gatsby.js

Two types of responsive images

There are two types of responsive images supported by gatsby-image.

  1. Images that have a fixed width and height
  2. Images that stretch across a fluid container

In the first scenario, you want to vary the image’s size for different screen resolutions — in other words, create retina images.

For the second scenario, you want to create multiple sizes of thumbnails for devices with widths stretching from smartphone to wide desktop monitors.

To decide between the two, ask yourself: “do I know the exact size this image will be?” If yes, it’s the first type. If no and its width and/or height need to vary depending on the size of the screen, then it’s the second type.

In Gatsby’s GraphQL implementation, you query for the first type by querying a child object of an image called resolutions — which you can see in the sample component above. For the second type, you do a similar query but for a child object called sizes.

Fragments

GraphQL includes a concept called “query fragments”. Which, as the name suggests, are a part of a query that can be used in multiple queries. To ease building with gatsby-image, Gatsby image processing plugins which support gatsby-image ship with fragments which you can easily include in your queries.

Note, due to a limitation of GraphiQL, you can not currently use these fragments in the GraphiQL IDE.

Plugins supporting gatsby-image currently include gatsby-transformer-sharp, gatsby-source-contentful and gatsby-source-datocms.

Their fragments are:

gatsby-transformer-sharp

  • GatsbyImageSharpResolutions
  • GatsbyImageSharpResolutions_noBase64
  • GatsbyImageSharpResolutions_tracedSVG
  • GatsbyImageSharpResolutions_withWebp
  • GatsbyImageSharpResolutions_withWebp_noBase64
  • GatsbyImageSharpResolutions_withWebp_tracedSVG
  • GatsbyImageSharpSizes
  • GatsbyImageSharpSizes_noBase64
  • GatsbyImageSharpSizes_tracedSVG
  • GatsbyImageSharpSizes_withWebp
  • GatsbyImageSharpSizes_withWebp_noBase64
  • GatsbyImageSharpSizes_withWebp_tracedSVG

gatsby-source-contentful

  • GatsbyContentfulResolutions
  • GatsbyContentfulResolutions_noBase64
  • GatsbyContentfulResolutions_withWebp
  • GatsbyContentfulResolutions_withWebp_noBase64
  • GatsbyContentfulSizes
  • GatsbyContentfulSizes_noBase64
  • GatsbyContentfulSizes_withWebp
  • GatsbyContentfulSizes_withWebp_noBase64

gatsby-source-datocms

  • GatsbyDatoCmsResolutions
  • GatsbyDatoCmsResolutions_noBase64
  • GatsbyDatoCmsSizes
  • GatsbyDatoCmsSizes_noBase64

If you don’t want to use the blur-up effect, choose the fragment with noBase64 at the end. If you want to use the traced placeholder SVGs, choose the fragment with tracedSVG at the end.

If you want to automatically use WebP images when the browser supports the file format, use the withWebp fragments. If the browser doesn’t support WebP, gatsby-image will fall back to the default image format.

Please see the gatsby-plugin-sharp documentation for more information on tracedSVG and its configuration options.

“Resolutions” queries

Component

Pass in the data returned from the resolutions object in your query via the resolutions prop. e.g. <Img resolutions={resolutions} />

Query

{
  imageSharp {
    # Other options include height (set both width and height to crop),
    # grayscale, duotone, rotate, etc.
    resolutions(width: 400) {
      # Choose either the fragment including a small base64ed image, a traced placeholder SVG, or one without.
      ...GatsbyImageSharpResolutions
    }
  }
}

“Sizes” queries

Component

Pass in the data returned from the sizes object in your query via the sizes prop. e.g. <Img sizes={sizes} />

Query

{
  imageSharp {
    # i.e. the max width of your container is 700 pixels.
    #
    # Other options include maxHeight (set both maxWidth and maxHeight to crop),
    # grayscale, duotone, rotate, etc.
    sizes(maxWidth: 700) {
      # Choose either the fragment including a small base64ed image, a traced placeholder SVG, or one without.
      ...GatsbyImageSharpSizes_noBase64
    }
  }
}

gatsby-image props

Name Type Description
resolutions object Data returned from the resolutions query
sizes object Data returned from the sizes query
fadeIn bool Defaults to fading in the image on load
title string Passed to the img element
alt string Passed to the img element
className string / object Passed to the wrapper element. Object is needed to support Glamor’s css prop
outerWrapperClassName string / object Passed to the outer wrapper element. Object is needed to support Glamor’s css prop
style object Spread into the default styles in the wrapper element
imgStyle object Spread into the default styles for the actual img element
position string Defaults to relative . Pass in absolute to make the component absolute positioned
backgroundColor string|bool Set a colored background placeholder. If true, uses “lightgray” for the color. You can also pass in any valid color string.
onLoad func A callback that is called when the full-size image has loaded.
Tag string Which HTML tag to use for wrapping elements. Defaults to div .

Image processing arguments

gatsby-plugin-sharp supports many additional arguments for transforming your images like quality,sizeByPixelDensity,pngCompressionLevel,cropFocus,greyscale and many more. See its documentation for more.

Some other stuff to be aware of

  • If you want to set display: none; on a component using a resolutions prop, you need to also pass in to the style prop { display: 'inherit' }.* Images don’t load until JavaScript is loaded. Gatsby’s automatic code splitting generally makes this fine but if images seem slow coming in on a page, check how much JavaScript is being loaded there.

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