getFluidGatsbyImage.js

import _ from 'lodash'
import qs from 'qs'
// @see https://www.contentful.com/developers/docs/references/images-api/#/reference/resizing-&-cropping/specify-width-&-height
const CONTENTFUL_IMAGE_MAX_SIZE = 4000

const isImage = image =>
  _.includes(
    [`image/jpeg`, `image/jpg`, `image/png`, `image/webp`, `image/gif`],
    _.get(image, `file.contentType`)
  )

const getBasicImageProps = (image, args) => {
  let aspectRatio
  if (args.width && args.height) {
    aspectRatio = args.width / args.height
  } else {
    aspectRatio =
      image.file.details.image.width / image.file.details.image.height
  }

  return {
    baseUrl: image.file.url,
    contentType: image.file.contentType,
    aspectRatio,
    width: image.file.details.image.width,
    height: image.file.details.image.height,
  }
}

const createUrl = (imgUrl, options = {}) => {
  // Convert to Contentful names and filter out undefined/null values.
  const args = _.pickBy(
    {
      w: options.width,
      h: options.height,
      fl: options.jpegProgressive ? `progressive` : null,
      q: options.quality,
      fm: options.toFormat || ``,
      fit: options.resizingBehavior || ``,
      f: options.cropFocus || ``,
      bg: options.background || ``,
    },
    _.identity
  )
  return `${imgUrl}?${qs.stringify(args)}`
}

export const getFluidGatsbyImage = (image, options) => {
  if (!isImage(image)) return null

  console.log(image)

  const { baseUrl, width, aspectRatio } = getBasicImageProps(image, options)

  let desiredAspectRatio = aspectRatio

  // If no dimension is given, set a default maxWidth
  if (options.maxWidth === undefined && options.maxHeight === undefined) {
    options.maxWidth = 800
  }

  // If only a maxHeight is given, calculate the maxWidth based on the height and the aspect ratio
  if (options.maxHeight !== undefined && options.maxWidth === undefined) {
    options.maxWidth = Math.round(options.maxHeight * desiredAspectRatio)
  }

  // If we're cropping, calculate the specified aspect ratio.
  if (options.maxHeight !== undefined && options.maxWidth !== undefined) {
    desiredAspectRatio = options.maxWidth / options.maxHeight
  }

  // If the users didn't set a default sizes, we'll make one.
  if (!options.sizes) {
    options.sizes = `(max-width: ${options.maxWidth}px) 100vw, ${options.maxWidth}px`
  }

  // Create sizes (in width) for the image. If the max width of the container
  // for the rendered markdown file is 800px, the sizes would then be: 200,
  // 400, 800, 1200, 1600, 2400.
  //
  // This is enough sizes to provide close to the optimal image size for every
  // device size / screen resolution
  let fluidSizes = []
  fluidSizes.push(options.maxWidth / 4)
  fluidSizes.push(options.maxWidth / 2)
  fluidSizes.push(options.maxWidth)
  fluidSizes.push(options.maxWidth * 1.5)
  fluidSizes.push(options.maxWidth * 2)
  fluidSizes.push(options.maxWidth * 3)
  fluidSizes = fluidSizes.map(Math.round)

  // Filter out sizes larger than the image's maxWidth and the contentful image's max size.
  const filteredSizes = fluidSizes.filter(size => {
    const calculatedHeight = Math.round(size / desiredAspectRatio)
    return (
      size <= CONTENTFUL_IMAGE_MAX_SIZE &&
      calculatedHeight <= CONTENTFUL_IMAGE_MAX_SIZE &&
      size <= width
    )
  })

  // Add the original image (if it isn't already in there) to ensure the largest image possible
  // is available for small images.
  if (
    !filteredSizes.includes(parseInt(width)) &&
    parseInt(width) < CONTENTFUL_IMAGE_MAX_SIZE &&
    Math.round(width / desiredAspectRatio) < CONTENTFUL_IMAGE_MAX_SIZE
  ) {
    filteredSizes.push(width)
  }

  // Sort sizes for prettiness.
  const sortedSizes = _.sortBy(filteredSizes)

  // Create the srcSet.
  const srcSet = sortedSizes
    .map(width => {
      const h = Math.round(width / desiredAspectRatio)
      return `${createUrl(image.file.url, {
        ...options,
        width,
        height: h,
      })} ${Math.round(width)}w`
    })
    .join(`,\n`)

  return {
    aspectRatio: desiredAspectRatio,
    baseUrl,
    src: createUrl(baseUrl, {
      ...options,
      width: options.maxWidth,
      height: options.maxHeight,
    }),
    srcSet,
    sizes: options.sizes,
  }
}

@Seth-Carter glad to hear that! There's an upcoming version of the contentful source that will allow us to query for gatsby image and also fixes a lot of rich text problems.

Wow, thanks so much. After trying loads of different solutions, this finally worked for me.

Thank you!

To the folks who are currently using this or about to use it, there's an upcoming update on the gatsby-source-contentful . See here: gatsbyjs/gatsby#25249

You can do an npm install gatsby-source-contentful@next if you wanna give it a try.

The new update would allow us to reference images straight to rich text so you won't hopefully have to use this hack. Note though that it has breaking changes.

I've been using it for my new projects and have little issues so far. And the best part is querying reference fields inside rich text. Those were harder to "hack" because we didn't have utility like it similar to gatsby-images.

Thanks for the headsup, I already tried it before using your solution. Sadly when using gatsby-source-contentful@next I got a couple of errors which I wasn't really in the mood for debugging for a not yet released version.

P.s. do you have an ETA when the update will be shipped?

@daydream05 thanks for keeping this updated. I'm going to try gatsby-source-contentful@next, wading through the errors seems worth it.

@daydream05 any idea why I'm getting a 'Check render method of ...' error? All the options appear to be returning the expected values.

@samh21 can you share the code for the News component? This error happens if your component is not returning anything.

The new version of contentful source is live at gatsby-source-contentful@4.0.0!

Thanks for the headsup, do you have a link to the relevant changes to this topic?

https://github.com/gatsbyjs/gatsby/blob/master/docs/reference/release-notes/v2.26/index.md#gatsby-source-contentful400

Thank you!

Thanks for great solution. Finally solved fluid image issue after trying every solution out there.