npm package: @lgenzelis/gatsby-remark-images
Description: Processes images in markdown so they can be used in the production build.
Author: Kyle Mathews
Latest version: 3.1.20

# gatsby-remark-images

Processes images in markdown so they can be used in the production build.

In the processing, it make images responsive by:

- Adding an elastic container to hold the size of the image while it loads to
  avoid layout jumps.
- Generating multiple versions of images at different widths and sets the
  `srcset` and `sizes` of the `img` element so regardless of the width of the
  device, the correct image is downloaded.
- Using the "blur up" technique popularized by [Medium][1] and [Facebook][2]
  where a small 20px wide version of the image is shown as a placeholder until
  the actual image is downloaded.

## Install

`npm install --save gatsby-remark-images gatsby-plugin-sharp`

## How to use

```javascript
// In your gatsby-config.js
plugins: [
  `gatsby-plugin-sharp`,
  {
    resolve: `gatsby-transformer-remark`,
    options: {
      plugins: [
        {
          resolve: `gatsby-remark-images`,
          options: {
            // It's important to specify the maxWidth (in pixels) of
            // the content container as this plugin uses this as the
            // base for generating different widths of each image.
            maxWidth: 590,
          },
        },
      ],
    },
  },
]
```

## Options

| Name                   | Default | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| ---------------------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `maxWidth`             | `650`   | The `maxWidth` in pixels of the div where the markdown will be displayed. This value is used when deciding what the width of the various responsive thumbnails should be.                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| `linkImagesToOriginal` | `true`  | Add a link to each image to the original image. Sometimes people want to see a full-sized version of an image e.g. to see extra detail on a part of the image and this is a convenient and common pattern for enabling this. Set this option to false to disable this behavior.                                                                                                                                                                                                                                                                                                                                                    |
| `showCaptions`         | `false` | Add a caption to each image with the contents of the title attribute, when this is not empty. If the title attribute is empty but the alt attribute is not, it will be used instead. Set this option to true to enable this behavior. You can also pass an array instead to specify which value should be used for the caption — for example, passing `['alt', 'title']` would use the alt attribute first, and then the title. When this is set to `true` it is the same as passing `['title', 'alt']`. If you just want to use the title (and omit captions for images that have alt attributes but no title), pass `['title']`. |
| `markdownCaptions`     | `false` | Parse the caption as markdown instead of raw text. Ignored if `showCaptions` is `false`.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| `sizeByPixelDensity`   | `false` | Analyze images' pixel density to make decisions about target image size. This is what GitHub is doing when embedding images in tickets. This is a useful setting for documentation pages with a lot of screenshots. It can have unintended side effects on high pixel density artworks.<br /><br />Example: A screenshot made on a retina screen with a resolution of 144 (e.g. Macbook) and a width of 100px, will be rendered at 50px.                                                                                                                                                                                           |
| `wrapperStyle`         |         | Add custom styles to the div wrapping the responsive images. Use the syntax for the style attribute e.g. `margin-bottom:10px; background: red;` or a function returning a style string which receives the information about the image you can use to dynamically set styles based on the aspectRatio for example.                                                                                                                                                                                                                                                                                                                  |
| `backgroundColor`      | `white` | Set the background color of the image to match the background image of your design.<br /><br />**Note:**<br />- set this option to `transparent` for a transparent image background.<br /> - set this option to `none` to completely remove the image background.                                                                                                                                                                                                                                                                                                                                                                  |
| `quality`              | `50`    | The quality level of the generated files.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| `withWebp`             | `false` | Additionally generate WebP versions alongside your chosen file format. They are added as a srcset with the appropriate mimetype and will be loaded in browsers that support the format. Pass `true` for default support, or an object of options to specifically override those for the WebP files. For example, pass `{ quality: 80 }` to have the WebP images be at quality level 80.                                                                                                                                                                                                                                            |
| `tracedSVG`            | `false` | Use traced SVGs for placeholder images instead of the "blur up" effect. Pass `true` for traced SVGs with the default settings (seen [here][3]), or an object of options to override the defaults. For example, pass `{ color: "#F00", turnPolicy: "TURNPOLICY_MAJORITY" }` to change the color of the trace to red and the turn policy to TURNPOLICY_MAJORITY. See [`node-potrace` parameter documentation][4] for a full listing and explanation of the available options.                                                                                                                                                        |
| `loading`              | `lazy`  | Set the browser's native lazy loading attribute. One of `lazy`, `eager` or `auto`.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |

## dynamic wrapperStyle example

```
{
  resolve: `gatsby-remark-images`,
  options: {
    maxWidth: 800,
    wrapperStyle: fluidResult => `flex:${_.round(fluidResult.aspectRatio, 2)};`,
  },
}
```

## Supported Formats

This plugin will support the following formats:

- JPEG
- PNG

Since [Sharp][5] is used for image processing, this plugin will not support GIFs or SVGs. If you would like to render these file types with the image markdown syntax, use the [gatsby-remark-copy-linked-files](https://www.gatsbyjs.org/packages/gatsby-remark-copy-linked-files/) plugin. Do note with this it will load in the images, but won't use the features of [Sharp][5] such as the elastic container or the blur-up enhancements.

[1]: https://jmperezperez.com/medium-image-progressive-loading-placeholder/
[2]: https://code.facebook.com/posts/991252547593574/the-technology-behind-preview-photos/
[3]: https://www.npmjs.com/package/gatsby-plugin-sharp#tracedsvg
[4]: https://github.com/tooolbox/node-potrace#parameters
[5]: https://github.com/lovell/sharp