Importing DTCG colours in srgb-linear or with alpha gives the wrong colour

[rubenvdlinde]

When a W3C design tokens file gives a colour as components, the import writes the wrong colour in two cases. An srgb-linear colour comes out too dark, and any alpha is dropped, so a translucent colour becomes opaque.

Where, at development fd992ea:

• lib/Service/DesignTokensMapper.php:57 accepts both srgb and srgb-linear as colour spaces.
• lib/Service/DesignTokensMapper.php:611-633 serializeColorObject() sends both spaces to the same converter when there is no hex.
• lib/Service/DesignTokensMapper.php:644-652 componentsToHex() scales each component by 255 without the sRGB transfer function, and writes three channels only.
  

  thematiq/lib/Service/DesignTokensMapper.php

  Lines 611 to 652 in fd992ea

  	$colorSpace = strtolower((string)($value['colorSpace'] ?? ''));
  	if (in_array($colorSpace, self::SRGB_COLOR_SPACES, true) === false) {
  	return ['ok' => false, 'reason' => 'unsupported-color-space', 'detail' => ($value['colorSpace'] ?? 'unknown')];
  	}
  	if (isset($value['hex']) === true && is_string($value['hex']) === true) {
  	$hex = $value['hex'];
  	if (str_starts_with($hex, '#') === false) {
  	$hex = '#' . $hex;
  	}
  	return ['ok' => true, 'value' => $hex];
  	}
  	if (isset($value['components']) === true
  	&& is_array($value['components']) === true
  	&& count($value['components']) >= 3
  	) {
  	return ['ok' => true, 'value' => $this->componentsToHex(components: array_values($value['components']))];
  	}
  	return ['ok' => false, 'reason' => 'unsupported-value-shape'];
  	}//end serializeColorObject()
  	/**
  	* Serialize three 0–1 sRGB float components to a `#rrggbb` hex literal.
  	*
  	* @param array<int, mixed> $components The `[r, g, b]` components (0–1 range, clamped).
  	*
  	* @return string The `#rrggbb` hex literal.
  	*
  	* @spec openspec/specs/custom-token-sets/spec.md
  	*/
  	private function componentsToHex(array $components): string {
  	$hex = '#';
  	foreach ([0, 1, 2] as $index) {
  	$channel = max(0.0, min(1.0, (float)$components[$index]));
  	$hex .= str_pad(dechex((int)round($channel * 255)), 2, '0', STR_PAD_LEFT);
  	}
  	return $hex;
  	}//end componentsToHex()

Linear light values must go through the sRGB transfer function before scaling. Without it, a linear 0.5 grey becomes #808080 instead of about #bcbcbc. The colour object's alpha is never read. Neither case is reported, so the imported set looks correct and renders differently.

Specified fix: openspec/changes/authoring-dtcg-export (requirement "W3C Design Tokens JSON Import", task 2.2).

Found by the OpenSpec pass on 27 Sep 2026 and re-read at fd992ea on 28 Sep.

Live check: import a token file with {"colorSpace": "srgb-linear", "components": [0.5, 0.5, 0.5], "alpha": 0.5} and read the stored value #808080.

[github-actions]

Thank you for opening this issue! It has been assigned to @rubenvdlinde for review.

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Triage labels:

• triage:accept-feature — accepted as a new feature
• triage:accept-bugfix — accepted as a bug fix
• triage:needs-info — more information needed
• triage:wontfix — will not be addressed
• triage:duplicate — duplicate of another issue

[rubenvdlinde]

Fixed in #702 (merged into development). srgb-linear components now go through the sRGB transfer function, and an alpha below 1 is kept as an 8-digit hex.