gatsby-remark-custom-image-component

npm install gatsby-remark-custom-image-component
yarn add gatsby-remark-custom-image-component

// gatsby-config.js
module.exports = {
  plugins: [
    {
      resolve: `gatsby-transformer-remark`,
      options: {
        plugins: [
          {
            resolve: `gatsby-remark-custom-image-component`,
            options: {
              // plugin options
              componentName: 'image-wrapper',
              imagePropName: 'src',
              sharpMethod: 'fluid',
              // fluid's arguments
              quality: 50,
              maxWidth: 800,
            }
          },
        ],
      },
    },

# src/content/hello-word/index.md
---
title: Hello World
date: '2015-05-01T22:12:03.284Z'
---

<image-wrapper src='./hero.jpg'></image-wrapper>

//src/components/ImageWrapper.js
import React from 'react'

// the result of sharp's image transformation will be passed directly to this component.
// so if you use `fluid` as `sharpMethod`, you'll get
// src, srcSet, base64, aspectRatio, srcSetType, sizes, density, originalImage. 
// Please refer to `gatsby-plugin-sharp` docs.
const ImageWrapper =  ({ src, srcSet }) => <img src={src} srcSet={srcSet} />

export { ImageWrapper }

//src/templates/blog-post.js
import React from 'react'
import rehypeReact from 'rehype-react'
import { ImageWrapper } from '../components/ImageWrapper'

const renderAst = new rehypeReact({
  createElement: React.createElement,
  components: { 'image-wrapper': ImageWrapper }, // register our component
}).Compiler

const BlogPostTemplate = ({ data }) => {
  const post = this.props.data.markdownRemark
  return <div>{ renderAst(post.htmlAst) }</div>
}

export default BlogPostTemplate

export const pageQuery = graphql`
  query BlogPostBySlug($slug: String!) {
    markdownRemark(fields: { slug: { eq: $slug } }) {
      htmlAst
    }
  }
`