chore: images post

src/posts/2024/check-if-images-are-available-before-optimizing-in-eleventy.md

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+---
+date: '2024-02-05'
+title: 'Check if images are available before optimizing in Eleventy'
+description: 'How to check if a remote image is available before attempting to optimize it using @11ty/eleventy-img.'
+tags: ['development', 'javascript', 'Eleventy']
+---
+I updated my image shortcode recently to leverage [Lene Saile](https://www.lenesaile.com)'s shortcode in the ever-useful [eleventy-excellent](https://github.com/madrilene/eleventy-excellent) project. As part of making this change, I also wanted to address build issues I had been facing when attempting to fetch and display avatars in webmentions (in the interest of improving post page performance).<!-- excerpt -->
+
+When fetching webmention avatars I would see occasional issues where one would be unavailable and cause the build to fail when it encountered a response other than `200`. To work around this, I created a simple message to check the headers for remote images before attempting to optimize them, which looks like this:
+
+```javascript
+const imageExists = async () => {
+  try {
+    return await fetch(src, { method: 'HEAD' }).then((res) => res.ok);
+  } catch {
+    return false;
+  }
+};
+```
+
+This returns a simple `boolean` that can be checked before calling `Image` from `@11ty/eleventy-img`. Additionally, we don't want to fetch locally stored images and, as such, we check whether an image `isLocal` before calling `imageExists`:
+
+```javascript
+const isLocal = src.includes('src/assets');
+```
+
+The full code is below, but the actual image is returned out of this fun, fun nested ternary:
+
+```javascript
+return isLocal ? await generateImage() : await imageExists().then(async (exists) => (exists ? await generateImage() : await generatePlaceholder()));
+```
+
+If an image is local, `generateImage()`, otherwise check if the `imageExists()` then either `generateImage()` or `generatePlaceholder()`. The placeholder, in my case, is a div with a black background an an `svg` captured and passed into the `image` shortcode for cases where I expect some failures (remote images outside of the CDN I use, mostly).
+
+```javascript
+import Image from '@11ty/eleventy-img';
+import path from 'path';
+import htmlmin from 'html-minifier-terser';
+
+const stringifyAttributes = (attributeMap) =>
+  Object.entries(attributeMap)
+    .map(([attribute, value]) => (value === undefined ? '' : `${attribute}="${value}"`))
+    .join(' ');
+
+export const img = async (
+  src,
+  alt = '',
+  className,
+  loading = 'lazy',
+  shape = '',
+  icon,
+  maxWidth = 1248,
+  sizes = '90vw',
+  formats = ['avif', 'webp', 'jpeg']
+) => {
+  const isLocal = src.includes('src/assets');
+  const imageExists = async () => {
+    try {
+      return await fetch(src, { method: 'HEAD' }).then((res) => res.ok);
+    } catch {
+      return false;
+    }
+  };
+
+  const generateImage = async () => {
+    const widths = [320, 570, 880, 1024, 1248];
+    const metadata = await Image(src, {
+      widths: widths.filter((width) => width <= maxWidth),
+      formats: [...formats],
+      outputDir: './_site/assets/img/cache/',
+      urlPath: '/assets/img/cache/',
+      filenameFormat: (id, src, width, format) => {
+        const { name } = path.parse(src);
+        return `${name}-${width}w.${format}`;
+      },
+    });
+    const lowsrc = metadata.jpeg[metadata.jpeg.length - 1];
+    const imageSources = Object.values(metadata)
+      .map(
+        (imageFormat) =>
+          `<source type="${imageFormat[0].sourceType}" srcset="${imageFormat
+            .map((entry) => entry.srcset)
+            .join(', ')}" sizes="${sizes}">`
+      )
+      .join('\n');
+    const imgageAttributes = stringifyAttributes({
+      src: lowsrc.url,
+      width: lowsrc.width,
+      height: lowsrc.height,
+      alt,
+      class: className,
+      loading,
+      decoding: 'async',
+    });
+    const imageElement = `<picture>${imageSources}<img ${imgageAttributes} /></picture>`;
+
+    return htmlmin.minify(imageElement, { collapseWhitespace: true });
+  };
+
+  const generatePlaceholder = async () => {
+    return htmlmin.minify(
+      `<div class="flex--centered image__placeholder ${shape}">${icon}</div>`,
+      { collapseWhitespace: true }
+    );
+  };
+
+  return isLocal ? await generateImage() : await imageExists().then(async (exists) => (exists ? await generateImage() : await generatePlaceholder()));
+};
+```
+
+Here's an example use case from my `interaction.liquid` partial used in my webmentions implementation:
+
+{% raw %}
+```liquid
+{% capture authorAlt %}{{ mention.author.name | escape }}{% endcapture %}
+{% capture fallbackIcon %}{% tablericon "user" authorAlt %}{% endcapture %}
+{% image mention.author.photo, authorAlt, 'avatar__image', 'lazy', 'square', fallbackIcon %}
+```
+{% endraw %}
+
+With all that in place I can now build my site, check if an image exists and spit out a servicable placeholder without failing the build.