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[@astrojs/image] flatten background only if alpha channel isn't supported #4800

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merged 5 commits into from
Sep 20, 2022
Merged

[@astrojs/image] flatten background only if alpha channel isn't supported #4800

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dc57918
Use sharp flatten only when format doesnt support alpha
obennaci Sep 18, 2022
466bcdc
Allow rgba for background prop
obennaci Sep 18, 2022
16e459b
Add changeset
obennaci Sep 18, 2022
4bb01d4
Adjust doc
obennaci Sep 19, 2022
203aa8c
Fix tests
obennaci Sep 19, 2022
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5 changes: 5 additions & 0 deletions .changeset/grumpy-monkeys-watch.md
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@@ -0,0 +1,5 @@
---
'@astrojs/image': patch
---

Prevent background flattening on formats supporting transparency
8 changes: 5 additions & 3 deletions packages/integrations/image/README.md
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Expand Up @@ -195,15 +195,17 @@ A `number` can also be provided, useful when the aspect ratio is calculated at b
**Default:** `undefined`
</p>

The background color to use for replacing the alpha channel with `sharp`'s `flatten` method. In case the output format
The background color is used to fill the remaining background when using `contain` for the `fit` property.

The background color is also used for replacing the alpha channel with `sharp`'s `flatten` method. In case the output format
doesn't support transparency (i.e. `jpeg`), it's advisable to include a background color, otherwise black will be used
as default replacement for transparent pixels.

The parameter accepts a `string` as value.

The parameter can be a [named HTML color](https://www.w3schools.com/tags/ref_colornames.asp), a hexadecimal
color representation with 3 or 6 hexadecimal characters in the form `#123[abc]`, or an RGB definition in the form
`rgb(100,100,100)`.
color representation with 3 or 6 hexadecimal characters in the form `#123[abc]`, an RGB definition in the form
`rgb(100,100,100)`, an RGBA definition in the form `rgba(100,100,100, 0.5)`.

#### fit

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4 changes: 3 additions & 1 deletion packages/integrations/image/src/loaders/index.ts
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Expand Up @@ -19,7 +19,9 @@ export type ColorDefinition =
| NamedColor
| `#${string}`
| `rgb(${number}, ${number}, ${number})`
| `rgb(${number},${number},${number})`;
| `rgb(${number},${number},${number})`
| `rgba(${number}, ${number}, ${number}, ${number})`
| `rgba(${number},${number},${number},${number})`

export type CropFit = 'cover' | 'contain' | 'fill' | 'inside' | 'outside';

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16 changes: 10 additions & 6 deletions packages/integrations/image/src/loaders/sharp.ts
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@@ -1,5 +1,10 @@
import sharp from 'sharp';
import { ColorDefinition, isAspectRatioString, isOutputFormat } from '../loaders/index.js';
import {
ColorDefinition,
isAspectRatioString,
isOutputFormat,
isOutputFormatSupportsAlpha,
} from '../loaders/index.js';
import type { OutputFormat, SSRImageService, TransformOptions } from './index.js';

class SharpService implements SSRImageService {
Expand Down Expand Up @@ -119,13 +124,12 @@ class SharpService implements SSRImageService {
});
}

// remove alpha channel and replace with background color if requested
if (transform.background) {
sharpImage.flatten({ background: transform.background });
}

if (transform.format) {
sharpImage.toFormat(transform.format, { quality: transform.quality });

if (transform.background && !isOutputFormatSupportsAlpha(transform.format)) {
sharpImage.flatten({ background: transform.background });
}
}

const { data, info } = await sharpImage.toBuffer({ resolveWithObject: true });
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11 changes: 11 additions & 0 deletions packages/integrations/image/test/background-color-image-ssg.test.js
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Expand Up @@ -106,6 +106,17 @@ describe('SSG image with background - build', function () {
id: '#rgb-spaced',
bg: [105, 105, 105],
},

{
title: 'RGBA color',
id: '#rgba',
bg: [105, 105, 105],
},
{
title: 'RGBA color with spaces',
id: '#rgba-spaced',
bg: [105, 105, 105],
},
].forEach(({ title, id, bg }) => {
it(title, async () => {
const image = $(id);
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28 changes: 25 additions & 3 deletions packages/integrations/image/test/background-color-image-ssr.test.js
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Expand Up @@ -31,7 +31,7 @@ describe('SSR image with background', function () {
title: 'Hex color',
id: '#hex',
query: {
f: 'avif',
f: 'jpeg',
w: '256',
h: '256',
href: /^\/assets\/file-icon.\w{8}.png/,
Expand All @@ -42,7 +42,7 @@ describe('SSR image with background', function () {
title: 'Hex color short',
id: '#hex-short',
query: {
f: 'png',
f: 'jpeg',
w: '256',
h: '256',
href: /^\/assets\/file-icon.\w{8}.png/,
Expand All @@ -53,7 +53,7 @@ describe('SSR image with background', function () {
title: 'RGB color',
id: '#rgb',
query: {
f: 'webp',
f: 'jpeg',
w: '256',
h: '256',
href: /^\/assets\/file-icon.\w{8}.png/,
Expand All @@ -71,6 +71,28 @@ describe('SSR image with background', function () {
bg: 'rgb(105, 105, 105)',
},
},
{
title: 'RGBA color',
id: '#rgba',
query: {
f: 'jpeg',
w: '256',
h: '256',
href: /^\/assets\/file-icon.\w{8}.png/,
bg: 'rgb(105,105,105,0.5)',
},
},
{
title: 'RGBA color with spaces',
id: '#rgba-spaced',
query: {
f: 'jpeg',
w: '256',
h: '256',
href: /^\/assets\/file-icon.\w{8}.png/,
bg: 'rgb(105, 105, 105, 0.5)',
},
},
].forEach(({ title, id, query }) => {
it(title, async () => {
const app = await fixture.loadTestAdapterApp();
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10 changes: 7 additions & 3 deletions packages/integrations/image/test/fixtures/background-color-image/src/pages/index.astro
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Expand Up @@ -9,13 +9,17 @@ import { Image } from '@astrojs/image/components';
<body>
<Image id="named" src={import('../assets/file-icon.png')} width={256} format="jpeg" background="dimgray" alt="named" />
<br />
<Image id="hex" src={import('../assets/file-icon.png')} width={256} format="avif" background="#696969" alt="hex" />
<Image id="hex" src={import('../assets/file-icon.png')} width={256} format="jpeg" background="#696969" alt="hex" />
<br />
<Image id="hex-short" src={import('../assets/file-icon.png')} width={256} background="#666" alt="hex-short" />
<Image id="hex-short" src={import('../assets/file-icon.png')} width={256} format="jpeg" background="#666" alt="hex-short" />
<br />
<Image id="rgb" src={import('../assets/file-icon.png')} width={256} format="webp" background="rgb(105,105,105)" alt="rgb" />
<Image id="rgb" src={import('../assets/file-icon.png')} width={256} format="jpeg" background="rgb(105,105,105)" alt="rgb" />
<br />
<Image id="rgb-spaced" src={import('../assets/file-icon.png')} width={256} format="jpeg" background="rgb(105, 105, 105)" alt="rgb-spaced" />
<br />
<Image id="rgba" src={import('../assets/file-icon.png')} width={256} format="jpeg" background="rgb(105,105,105,0.5)" alt="rgba" />
<br />
<Image id="rgba-spaced" src={import('../assets/file-icon.png')} width={256} format="jpeg" background="rgb(105, 105, 105, 0.5)" alt="rgba-spaced" />
<br />
</body>
</html>