Allow specifying image width via attribute in gatsby-remark-images

[alexlouden]

Summary

I've forked gatsby-remark-images and added the ability to specify a width for individual images: https://github.com/Bonobolabs/gatsby-remark-image-custom-widths

Basic example

Old:

![My image](./image.jpg)

New:

<img src="./image.jpg" alt="My image" width="500px"/>

This passes in 500px to the plugin's maxWidth option (so generated responsive images are 0.25x, 0.5x, 1x, 2x, 3x of 500px), and also styles the image wrapper class to max-width: 500px so it's displayed at that size.

I'm currently using this with mdx, but it can be used anywhere gatsby-remark-images is used.
gatsby-config:

    {
      resolve: 'gatsby-plugin-mdx',
      options: {
        extensions: ['.mdx', '.md'],
        plugins: [
          '@bonobolabs/gatsby-remark-images-custom-widths',
        ],
        gatsbyRemarkPlugins: [
          {
            resolve: '@bonobolabs/gatsby-remark-images-custom-widths',
            options: {
              maxWidth: 740,
              linkImagesToOriginal: false,
              quality: 80,
            }
          },
          ...

(I went with a width attribute in HTML as a first version since it's an existing spec, will render nicely in Github, and is supported by MDX/etc. This is also easier than agreeing on which syntax to use from all the different flavours of markdown, and ensuring that the markdown renderer will parse this consistently etc).

Motivation

At the moment, markdown images are always displayed at the full width of the page. This is a pretty simple change that adds support for images to be displayed at a custom width - e.g. for portrait orientation images, image galleries, or even just displaying two images side by side:

<div class="side-by-side">
<img src="image1.png" alt="Image one" width="300px"/>
<img src="image2.png" alt="Image two" width="300px"/>
</div>

.side-by-side: {
    display: flex;
    justify-content: space-evenly;
}
.side-by-side > span {
   flex: 1;
}

Alternatives

I think another way to achieve this would be with a custom image component (MDX/remark-component/etc), but I think that'd be quite difficult to implement (e.g. given that there's no support for dynamic graphql queries), wouldn't be as well supported by other plugins/sources, and adds a fair bit of complexity (a second way of processing/resizing/caching images).

[alexlouden]

Let me know if you think this would be a useful change and I'll make it into a proper PR :)

[LekoArts]

For my taste this is a bit too much magic and not really straightforward for other people to figure out. Take this as an example:

Theme A/Starter A uses this plugin, the end user doesn't know that it's in there and wants to use the <img /> tag instead of ![]() - but the person will then be surprised that it doesn't behave like expected.

You can also read previous discussions here: #2609

I'd prefer syntax like that.

[github-actions]

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[github-actions]

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[henrikwirth]

I believe this implementation is more than valid. Surely it would be nice to have a ![alt](src){attributes} syntax too, but as that is not a standard it would mess around with markdown that people write for different systems.

The <img /> approach instead is basic html and will be interpreted just fine in most cases. The magic from width to maxWidth is only hapening because of gatsby-image's wrapper that needs to be sized down. If gatsby-image is not in place, most other markdown parsers will just render the image with the given width.

I'd be very happy, if that makes it into the main plugin.

[zaeyon]

Thank you!!

[lookdeceline]

This sounds amazing! Definitely need it !

[musicbyjing]

Absolutely!

[suhasdara]

I would like this. Really hard to work around it, if anyone knows how to make dynamic maxWidth possible, please let me know

[NiallLDY]

Is there any solution here at present? How to specify the size of the picture in markdown?

[ejscribner]

+1 wondering if theres a solution to this?

[simplenotezy]

@henrikwirth you could also consider adding support for width like Mou or Marked 2 does it

[andrewd72]

I'm stuggling with this also.
There are a few things I can do easily with the Hugo version of my photo blog - one is to be very exact about the sizes of images with two side by side.
If a couple of images are 4 times too big it isn't so bad but if there are 20 side by side images in between full width images, the performance hit is significant.