Draw a COLR version 1 font in colour (#76)

src/Fonts/Color/ColorFontFile.php

@@ -9,12 +9,17 @@
 
 /**
  * An open font, as each ColorGlyphSource drawing it reads it: its tables, its file, the log a glyph
- * that cannot be drawn is reported to, and its outlines, decoded once for every source that draws
- * with them.
+ * that cannot be drawn is reported to, and its outlines and palette, read once for every source that
+ * draws with them.
  */
 class ColorFontFile
 {
 
+	/**
+	 * The palette index COLR gives a colour that is the colour of the text
+	 */
+	const FOREGROUND = 0xFFFF;
+
 	/**
 	 * @var FileReader
 	 */
@@ -40,6 +45,11 @@ class ColorFontFile
 	 */
 	private $outline;
 
+	/**
+	 * @var int[][]|null
+	 */
+	private $palette;
+
 	/**
 	 * @param TTFontFile      $font       The font, its table directory read
 	 * @param FileReader      $reader     The font file
@@ -75,4 +85,56 @@ public function outline()
 
 		return $this->outline;
 	}
+
+	/**
+	 * The first palette of CPAL, the one a COLR font is drawn in. Every read is checked for coming up
+	 * short - see FontReader::fieldsAt().
+	 *
+	 * @return int[][] Each colour as [red, green, blue, alpha] from 0 to 255, or none where CPAL has no
+	 *                 palette or its first runs past the colour records
+	 */
+	public function palette()
+	{
+		if ($this->palette !== null) {
+			return $this->palette;
+		}
+
+		$this->palette = [];
+		$cpal = $this->table('CPAL')[0];
+
+		// numPaletteEntries, numPalettes, numColorRecords, colorRecordsArrayOffset, colorRecordIndices[0]
+		$header = $this->reader->fieldsAt($cpal + 2, 12, 'nentries/npalettes/nrecords/Ncolors/nfirst');
+		if ($header === null || $header[1] === 0 || $header[4] + $header[0] > $header[2]) {
+			return $this->palette;
+		}
+
+		list($entries, , , $colors, $first) = $header;
+
+		// Each colour is stored blue, green, red, alpha
+		$bgra = $this->reader->fieldsAt($cpal + $colors + $first * 4, $entries * 4, 'C*');
+		for ($i = 0; $bgra !== null && $i < 4 * $entries; $i += 4) {
+			$this->palette[] = [$bgra[$i + 2], $bgra[$i + 1], $bgra[$i], $bgra[$i + 3]];
+		}
+
+		return $this->palette;
+	}
+
+	/**
+	 * @param int   $index An index into the first palette, or FOREGROUND
+	 * @param float $alpha The paint's alpha, from 0 to 1, which the colour's own is multiplied by
+	 *
+	 * @return array [[red, green, blue] from 0 to 1, or null for the colour of the text, alpha]. An index
+	 *               the palette does not hold is the colour of the text too.
+	 */
+	public function colour($index, $alpha)
+	{
+		$palette = $this->palette();
+		if ($index === self::FOREGROUND || !isset($palette[$index])) {
+			return [null, min(1, $alpha)];
+		}
+
+		list($red, $green, $blue, $own) = $palette[$index];
+
+		return [[$red / 255, $green / 255, $blue / 255], min(1, $alpha) * $own / 255];
+	}
 }

src/Fonts/Color/ColorFormats.php

@@ -12,9 +12,14 @@ class ColorFormats
 
 	/**
 	 * The formats mPDF can draw, each with the ColorGlyphSource that draws it, in the order a font that
-	 * carries several is drawn in
+	 * carries several is drawn in.
+	 *
+	 * Whether a font is drawable is kept in its cached metrics - see drawable() - so adding a format
+	 * here calls for raising MetricsGenerator::CACHE_FORMAT, or a font of that format cached before is
+	 * served as one that is not.
 	 */
 	const SOURCES = [
+		'COLRv1' => 'Mpdf\Fonts\Color\ColrV1Source',
 		'COLRv0' => 'Mpdf\Fonts\Color\ColrV0Source',
 		'CBDT' => 'Mpdf\Fonts\Color\CbdtSource',
 		'sbix' => 'Mpdf\Fonts\Color\SbixSource',
@@ -51,21 +56,24 @@ public static function inColor(Mpdf $mpdf)
 	}
 
 	/**
-	 * The format a document draws a font in
+	 * Whether a document draws a font in colour: it carries a format mPDF draws, and the document may
+	 * draw colour
 	 *
 	 * @param array $font The font, as Mpdf::$fonts holds it
 	 * @param Mpdf  $mpdf The document
 	 *
-	 * @return string The format, or '' where the font is not drawn in colour
+	 * @return bool
 	 */
-	public static function drawn(array $font, Mpdf $mpdf)
+	public static function drawsInColor(array $font, Mpdf $mpdf)
 	{
-		return empty($font['colorFormats']) ? '' : self::choose($font['colorFormats'], self::inColor($mpdf));
+		return !empty($font['colorFormats']) && self::drawable($font['colorFormats']) && self::inColor($mpdf);
 	}
 
 	/**
-	 * What draws a font's glyphs in a document, each glyph by the first that has it: the format it is
-	 * drawn in, where the document may draw colour, then its outlines, where it has any
+	 * What draws a font's glyphs in a document, each glyph by the first that has it: each format the
+	 * font carries, in the order of SOURCES, where the document may draw colour, then its outlines,
+	 * where it has any. A COLR version 1 font's glyph with no paint is so drawn from its version 0
+	 * layers.
 	 *
 	 * @param array $font The font, as Mpdf::$fonts holds it
 	 * @param Mpdf  $mpdf The document
@@ -74,8 +82,10 @@ public static function drawn(array $font, Mpdf $mpdf)
 	 */
 	public static function sources(array $font, Mpdf $mpdf)
 	{
-		$format = self::drawn($font, $mpdf);
-		$sources = $format === '' ? [] : [self::SOURCES[$format]];
+		$sources = [];
+		if (!empty($font['colorFormats']) && self::inColor($mpdf)) {
+			$sources = array_values(array_intersect_key(self::SOURCES, array_flip($font['colorFormats'])));
+		}
 		if (!empty($font['hasOutlines'])) {
 			$sources[] = 'Mpdf\Fonts\Color\OutlineSource';
 		}
@@ -96,19 +106,4 @@ public static function blank(array $font, Mpdf $mpdf)
 	{
 		return !empty($font['colorFormats']) && self::drawable($font['colorFormats']) && !self::sources($font, $mpdf);
 	}
-
-	/**
-	 * The format a font is drawn in: the first of SOURCES that it carries
-	 *
-	 * @param string[] $fontFormats The formats the font carries
-	 * @param bool     $color       Whether the document may use colour
-	 *
-	 * @return string The format, or '' where the font is drawn without colour
-	 */
-	public static function choose(array $fontFormats, $color)
-	{
-		$formats = $color ? array_intersect(array_keys(self::SOURCES), $fontFormats) : [];
-
-		return $formats ? reset($formats) : '';
-	}
 }