postcss-url not generating base64 url - sass

Question

I am building a library which is used as a package in a Next.js app.
I have a variable in my .scss file which uses an url('./some-file.png') and I want this to generate a base64 url in order to be used in my other app easily.
When I build the project, after adding postcss-url, the generated url has not changed...there is no base64 url generated.
rollup.config.js:
import peerDepsExternal from 'rollup-plugin-peer-deps-external'
import resolve from '#rollup/plugin-node-resolve'
import commonjs from '#rollup/plugin-commonjs'
import typescript from '#rollup/plugin-typescript'
import postcss from 'rollup-plugin-postcss'
import copy from 'rollup-plugin-copy'
import svgr from '#svgr/rollup'
import dts from 'rollup-plugin-dts'
import del from 'rollup-plugin-delete'
import analyze from 'rollup-plugin-analyzer'
import { terser } from 'rollup-plugin-terser'
import json from '#rollup/plugin-json'
import graphql from '#rollup/plugin-graphql'
import fs from 'fs'
import url from 'postcss-url'
import path from 'path'
import * as packageJson from './package.json'
const tsConfig = JSON.parse(fs.readFileSync(__dirname + '/tsconfig.json', 'utf8'))
export default [
{
input: 'src/index.ts',
output: [
{
file: packageJson.main,
format: 'cjs',
sourcemap: true
},
{
file: packageJson.module,
format: 'esm',
sourcemap: true
}
],
plugins: [
peerDepsExternal(),
copy({
targets: [
{
src: [
'src/ui/styles/palette.scss',
'src/ui/styles/themes.scss',
'src/ui/styles/urls.scss',
'src/ui/styles/_exports.module.scss'
],
dest: 'lib/scss'
},
{ src: 'src/assets/images', dest: 'lib/assets' }
],
verbose: true
}),
svgr({ dimensions: false }),
resolve({ preferBuiltins: true, mainFields: ['browser'] }),
postcss({
plugins: [
url({
url: "inline"
}),
],
extract: path.resolve('lib/styles.scss'),
}),
commonjs(),
json(),
typescript({ tsconfig: './tsconfig.json' }),
graphql(),
terser(),
analyze({ summaryOnly: true })
]
},
{
input: 'lib/types/src/index.d.ts',
output: [{ file: 'lib/index.d.ts', format: 'esm' }],
external: [/\.scss$/],
plugins: [
dts({
compilerOptions: {
baseUrl: '.',
paths: tsConfig.compilerOptions.paths
}
}),
del({ hook: 'buildEnd', targets: './lib/types' })
]
}
]
button.scss
#import '../../styles/themes.scss';
.background-color-header {
background: themed('header-background');
}
themes.scss
#import './urls.scss';
header-background: url($light-url) no-repeat #{','} $gradient-light-background-header,
and finally : urls.scss
$light-url: '/assets/images/my-image.png';
styles.scss which is the result of the build:
.background-color-header {
background: url("/assets/images/my-image.png") no-repeat , transparent linear-gradient(180deg, #faf8f4 0%, white 100%) 0% 0% no-repeat padding-box;
}
So, you can see that the url is not base64 ...
Any advice?