gatsby-image

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.

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 consistantly 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 simple 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.

This is what a component using gatsby-images 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 steps right in the query
        # Makes it trivial to update as your page's design changes.
        resolutions(width: 125, height: 125) {
          ...GatsbyImageSharpResolutions
        }
      }
    }
  }
`

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 and gatsby-source-contentful.

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
• GatsbyContentfulSizes
• GatsbyContentfulSizes_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`
outerWrapperClassName	`string	object`
style	object	Spread into the default styles in the wrapper div
position	string	Defaults to relative. Pass in absolute to make the component absolute positioned
backgroundColor	`string	bool`
onLoad	func	A callback that is called when the full-size image has loaded.

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.