80 lines
3.1 KiB
Plaintext
80 lines
3.1 KiB
Plaintext
---
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title: Images in Next.js
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date: '2020-11-11'
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tags: ['next js', 'guide']
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draft: false
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summary: 'In this article we introduce adding images in the tailwind starter blog and the benefits and limitations of the next/image component.'
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---
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# Introduction
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The tailwind starter blog has out of the box support for [Next.js's built-in image component](https://nextjs.org/docs/api-reference/next/image) and automatically swaps out default image tags in markdown or mdx documents to use the Image component provided.
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# Usage
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To use in a new page route / javascript file, simply import the image component and call it e.g.
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```js
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import Image from 'next/image'
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function Home() {
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return (
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<>
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<h1>My Homepage</h1>
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<Image src="/me.png" alt="Picture of the author" width={500} height={500} />
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<p>Welcome to my homepage!</p>
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</>
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)
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}
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export default Home
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```
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For a markdown file, the default image tag can be used and the default `img` tag gets replaced by the `Image` component in the build process.
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Assuming we have a file called `ocean.jpg` in `data/img/ocean.jpg`, the following line of code would generate the optimized image.
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```
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```
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Alternatively, since we are using mdx, we can just use the image component directly! Note, that you would have to provide a fixed width and height. The `img` tag method parses the dimension automatically.
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```js
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<Image alt="ocean" src="/static/images/ocean.jpg" width={256} height={128} />
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```
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_Note_: If you try to save the image, it is in webp format, if your browser supports it!
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<p>
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Photo by{' '}
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<a href="https://unsplash.com/@yucar?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText">
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YUCAR FotoGrafik
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</a>{' '}
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on{' '}
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<a href="https://unsplash.com/s/photos/sea?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText">
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Unsplash
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</a>
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</p>
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# Benefits
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- Smaller image size with Webp (~30% smaller than jpeg)
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- Responsive images - the correct image size is served based on the user's viewport
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- Lazy loading - images load as they are scrolled to the viewport
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- Avoids [Cumulative Layout Shift](https://web.dev/cls/)
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- Optimization on demand instead of build-time - no increase in build time!
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# Limitations
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- Due to the reliance of `next/image`, unless you are using an external image CDN like Cloudinary or Imgix, it is practically required to use Vercel for hosting. This is because the component acts like a serverless function that calls a highly optimized image CDN.
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If you do not want to be tied to Vercel, you can remove `imgToJsx` in `remarkPlugins` in `lib/mdx.js`. This would avoid substituting the default `img` tag.
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Alternatively, one could wait for image optimization at build time to be supported. A different library, [next-optimized-images](https://github.com/cyrilwanner/next-optimized-images) does that, although it requires transforming the images through webpack which is not done here.
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- Images from external links are not passed through `next/image`
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- All images have to be stored in the `public` folder e.g `/static/images/ocean.jpeg`
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