Using Gatsby Image with Kentico Kontent

When building a website using Gatsby one of the incredibly useful packages is Gatsby Image. This package handles rendering responsive images with additional features such as lazy loading, traced SVGs and "blur-up" animation.  However, the official Kentico Kontent source plugin does not provide any support for the package out-of-the-box.

The Gatsby Image component expects either a FixedObject or FluidObject to be supplied; other plugins include GraphQL fields on File nodes which can be queried to generate these objects. For example, gatsby-transformer-sharp adds a childImageSharp field with fixed and fluid fields.

In order to bridge the gap and provide support for Gatsby Image we can use the createRemoteFileNode function exported by gatsby-source-filesystem to create File nodes within our GraphQL schema. This will download the remote asset and make it available to be processed by gatsby-transformer-sharp.

However, this approach has some downsides. 

• If there are a large number of assets then downloading can be a slow and time-consuming task. 
• Once the images have been downloaded they need to be processed by Sharp to generate the various image variants. On a relatively basic website with less than 100 unique assets this has been noted to add several minutes to the build time.

An alternative route would be to create a custom transformer plugin to leverage the image transformation API available with Kentico Kontent. Fortunately, this is exactly what I have created with the @rshackleton/gatsby-transformer-kontent-image package.

The plugin will create new fields on the existing KontentAsset type which provide the data required by Gatsby Image. They can be used by including them in your GraphQL queries as shown in the example below.

{
  allKontentItemArticle {
    nodes {
      elements {
        banner {
          value {
            fixed(width: 1000) {
              ...KontentAssetFixed
            }
          }
        }
      }
    }
  }
}

Finally, as using both the source plugin and the image transformer together would be a common requirement of any projects using Kentico Kontent, I have also created a new Gatsby Theme called @rshackleton/gatsby-theme-kontent. This includes both plugins as it's default configuration and accepts options for each. In the future I hope to expand the theme to include components that will assist in rendering linked items and components within rich text fields.