Write PDF/X-4 when PDFX is '4', keeping the transparency, layers and colour fonts PDF/X-1a strips

.github/workflows/pdfx4-policy.yml

@@ -0,0 +1,81 @@
+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+#
+# A veraPDF policy check over the features of mPDF's PDF/X-4 output. veraPDF has no PDF/X validation
+# profile, so this is NOT a conformance verdict - see utils/verapdf/pdfx4_policy.php.
+
+name: "PDF/X-4 Policy"
+
+on:
+  pull_request:
+  push:
+    branches:
+      - "master"
+      - "development"
+      - "test"
+      - "gravitypdf"
+
+jobs:
+
+  policy:
+
+    name: "veraPDF policy"
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v7"
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "8.5"
+          extensions: "mbstring, gd, bcmath, bz2"
+          tools: composer:v2
+          ini-values: error_reporting=-1
+
+      - name: "Install Java"
+        uses: "actions/setup-java@v5"
+        with:
+          distribution: "temurin"
+          java-version: "21"
+
+      - name: "Install veraPDF"
+        run: |
+          curl -fsSL -o verapdf-installer.zip https://software.verapdf.org/rel/verapdf-installer.zip
+          unzip -q verapdf-installer.zip -d "$RUNNER_TEMP"
+          cat > "$RUNNER_TEMP/auto-install.xml" <<XML
+          <?xml version="1.0" encoding="UTF-8" standalone="no"?>
+          <AutomatedInstallation langpack="eng">
+            <com.izforge.izpack.panels.htmlhello.HTMLHelloPanel id="welcome"/>
+            <com.izforge.izpack.panels.target.TargetPanel id="install_dir">
+              <installpath>$RUNNER_TEMP/verapdf</installpath>
+            </com.izforge.izpack.panels.target.TargetPanel>
+            <com.izforge.izpack.panels.packs.PacksPanel id="sdk_pack_select">
+              <pack index="0" name="veraPDF Mac and *nix Scripts" selected="true"/>
+              <pack index="1" name="veraPDF Validation model" selected="true"/>
+              <pack index="2" name="veraPDF Documentation" selected="false"/>
+              <pack index="3" name="veraPDF Sample Plugins" selected="false"/>
+            </com.izforge.izpack.panels.packs.PacksPanel>
+            <com.izforge.izpack.panels.install.InstallPanel id="install"/>
+            <com.izforge.izpack.panels.finish.FinishPanel id="finish"/>
+          </AutomatedInstallation>
+          XML
+          java -jar "$RUNNER_TEMP"/verapdf-greenfield-*/verapdf-izpack-installer-*.jar "$RUNNER_TEMP/auto-install.xml"
+          "$RUNNER_TEMP/verapdf/verapdf" --version
+          echo "VERAPDF_BIN=$RUNNER_TEMP/verapdf/verapdf" >> "$GITHUB_ENV"
+
+      - name: "Install dependencies"
+        run: "composer install --no-interaction --no-progress"
+
+      - name: "Policy check"
+        run: php utils/verapdf/pdfx4_policy.php "$VERAPDF_BIN"
+
+      - name: "Upload the documents"
+        if: failure()
+        uses: "actions/upload-artifact@v4"
+        with:
+          name: "pdfx4-policy-documents"
+          path: "tmp/verapdf"
+          if-no-files-found: "ignore"

composer.json

@@ -87,6 +87,7 @@
 		"arabicjoining:update": "@php utils/arabicjoining_update.php",
 		"emoji:update": "@php utils/emoji_update.php",
 		"fontcache:update": "@php utils/fontcache_update.php",
+		"grayprofile:update": "@php utils/grayprofile_update.php",
 		"otlanguages:update": "@php utils/otlanguages_update.php",
 		"otldump:update": "@php utils/otldump_update.php",
 		"shaping:update": "@php utils/shaping_update.php",

data/iccprofiles/NOTICE.md

@@ -6,15 +6,19 @@ licence — they are aggregated data assets, not part of mPDF's source code, and
 are redistributed here under the terms their publishers grant. Do not alter these
 files; ship them byte-for-byte.
 
-To use a different output condition (e.g. your house print profile), set the
-`ICCProfile` config key to the path of your own `.icc` file — it overrides the
-bundled default and nothing here is embedded.
+To use a different output condition (e.g. your house print profile, or an RGB
+output intent for PDF/X-4), set the `ICCProfile` config key to the path of your
+own `.icc` file — it overrides the bundled default. A PDF/X output intent must be
+an output device (`prtr`) profile.
 
 ---
 
 ## sRGB_IEC61966-2-1.icc
 
-- **Colour space:** RGB (used as the PDF/A and default output-intent profile).
+- **Colour space:** RGB, device class `mntr` (display). Used as the PDF/A
+  output-intent profile. Also the ICC-based colour space RGB is written in where
+  a PDF/X-4 document prints to a CMYK or grey output intent, which permits no
+  DeviceRGB. Being a display profile, it is not a PDF/X output intent.
 - **Publisher / copyright:** International Color Consortium.
 - **Embedded copyright string:** `Copyright International Color Consortium, 2009`.
 - **Terms:** Distributed by the ICC as a freely redistributable reference
@@ -24,8 +28,10 @@ bundled default and nothing here is embedded.
 ## SWOP2006_Coated3v2.icc
 
 - **Colour space:** CMYK, device class `prtr` (printer), ICC v2.
-  A CMYK output intent: point `ICCProfile` at it, with `restrictColorSpace` set
-  to 3, to write a CMYK PDF/A document. Nothing embeds it unless asked.
+  The output intent a **PDF/X-4** document embeds where it names no
+  `ICCProfile`, identified by the CGATS TR 003 characterisation it is built on.
+  Point `ICCProfile` at it, with `restrictColorSpace` set to 3, to write a CMYK
+  PDF/A document.
   Represents U.S. web-coated (SWOP) publication printing, 2006, grade 3 coated.
 - **Publisher:** IDEAlliance, with permission of X-Rite, Inc.
 - **Copyright:** X-Rite, Inc.

phpstan-baseline.neon

@@ -150,12 +150,6 @@ parameters:
 			count: 2
 			path: src/Image/ImageProcessor.php
 
-		-
-			message: '#^Variable \$info might not be defined\.$#'
-			identifier: variable.undefined
-			count: 1
-			path: src/Image/ImageProcessor.php
-
 		-
 			message: '#^Binary operation "\*" between 0\.3333333333333333 and string results in an error\.$#'
 			identifier: binaryOp.invalid
@@ -216,12 +210,6 @@ parameters:
 			count: 1
 			path: src/Image/Svg.php
 
-		-
-			message: '#^Variable \$color_final might not be defined\.$#'
-			identifier: variable.undefined
-			count: 1
-			path: src/Image/Svg.php
-
 		-
 			message: '#^Variable \$inners might not be defined\.$#'
 			identifier: variable.undefined

src/Color/ColorConverter.php

@@ -203,6 +203,63 @@ public function colAtoString($c)
 		return '';
 	}
 
+	/**
+	 * A shading function gives every stop of a gradient the same number of components, so the stops are
+	 * written in one colour space: grey where every stop is grey, CMYK where any is CMYK, keeping the
+	 * inks the document names, and RGB otherwise
+	 *
+	 * @param string[] $colors Binary color strings
+	 *
+	 * @return string 'Gray', 'RGB' or 'CMYK'
+	 */
+	public function gradientColorSpace(array $colors)
+	{
+		$space = 'Gray';
+
+		foreach ($colors as $c) {
+			if ($c[0] == static::MODE_CMYK || $c[0] == static::MODE_CMYKA) {
+				return 'CMYK';
+			}
+
+			if ($c[0] != static::MODE_GRAYSCALE) {
+				$space = 'RGB';
+			}
+		}
+
+		return $space;
+	}
+
+	/**
+	 * @param string $c     Binary color string
+	 * @param string $space The colour space gradientColorSpace() settled on for the stops
+	 *
+	 * @return string The colour's components in that space, as a shading function writes them
+	 */
+	public function gradientComponents($c, $space)
+	{
+		if ($c[0] == static::MODE_CMYK || $c[0] == static::MODE_CMYKA) {
+			return sprintf('%.3F %.3F %.3F %.3F', ord($c[1]) / 100, ord($c[2]) / 100, ord($c[3]) / 100, ord($c[4]) / 100);
+		}
+
+		if ($c[0] == static::MODE_GRAYSCALE) {
+			$gray = ord($c[1]) / 255;
+
+			if ($space === 'CMYK') {
+				return sprintf('0.000 0.000 0.000 %.3F', 1 - $gray);
+			}
+
+			return $space === 'RGB' ? sprintf('%.3F %.3F %.3F', $gray, $gray, $gray) : sprintf('%.3F', $gray);
+		}
+
+		if ($space === 'CMYK') {
+			$cmyk = $this->colorModeConverter->rgb2cmyk([static::MODE_RGB, ord($c[1]), ord($c[2]), ord($c[3])]);
+
+			return sprintf('%.3F %.3F %.3F %.3F', $cmyk[1] / 100, $cmyk[2] / 100, $cmyk[3] / 100, $cmyk[4] / 100);
+		}
+
+		return sprintf('%.3F %.3F %.3F', ord($c[1]) / 255, ord($c[2]) / 255, ord($c[3]) / 255);
+	}
+
 	/**
 	 * @param string $color
 	 * @param string[] $PDFAXwarnings

src/Color/ColorModeConverter.php

@@ -31,6 +31,10 @@ public function cmyk2gray($c)
 	}
 
 	/**
+	 * Black is the black ink alone. Painting it as all four inks at once - registration black - is 400%
+	 * total area coverage, past what any press allows, and would be a jump away from every near-black
+	 * value: rgb(1, 1, 1) is already K 99.6% and nothing else.
+	 *
 	 * @param float[] $c
 	 *
 	 * @return float[]
@@ -44,13 +48,10 @@ public function rgb2cmyk($c)
 
 		if ($min == 1) {
 			if ($c[0] == 5) {
-				return [6, 100, 100, 100, 100, $c[4]];
+				return [6, 0, 0, 0, 100, $c[4]];
 			}
 
-			return [4, 100, 100, 100, 100];
-			// For K-Black
-			//if ($c[0]==5) { return array (6,0,0,0,100, $c[4]); }
-			//else { return array (4,0,0,0,100); }
+			return [4, 0, 0, 0, 100];
 		}
 
 		$K = $min;

src/Color/ColorSpaceRestrictor.php

@@ -113,7 +113,20 @@ private function restrictSpotColorSpace($c, &$PDFAXwarnings = [])
 	 */
 	private function restrictRgbColorSpace($c, $color, &$PDFAXwarnings = [])
 	{
-		if ($this->mpdf->PDFX || ($this->mpdf->PDFA && $this->mpdf->restrictColorSpace == 3)) {
+		// PDF/X-4 keeps RGB as it is: printing to an RGB condition it is DeviceRGB, and printing to any
+		// other it is written in the ICC-based sRGB colour space, so that the press converts the colours
+		// of the content and of the images together - see Mpdf::writesCalibratedRgb()
+		if ($this->mpdf->isPdfx4()) {
+			if ($this->mpdf->pdfxRgbIntent()) {
+				return $c;
+			}
+
+			$gray = $this->neutralToGray($c);
+
+			return $gray === null ? $c : $gray;
+		}
+
+		if (($this->mpdf->PDFX && !$this->mpdf->pdfxRgbIntent()) || ($this->mpdf->PDFA && $this->mpdf->restrictColorSpace == 3)) {
 			if (($this->mpdf->PDFA && !$this->mpdf->PDFAauto) || ($this->mpdf->PDFX && !$this->mpdf->PDFXauto)) {
 				$PDFAXwarnings[] = "RGB color specified '" . $color . "' (converted to CMYK)";
 			}
@@ -136,8 +149,8 @@ private function restrictRgbColorSpace($c, $color, &$PDFAXwarnings = [])
 	 */
 	private function restrictCmykColorSpace($c, $color, &$PDFAXwarnings = [])
 	{
-		if ($this->mpdf->PDFA && $this->mpdf->restrictColorSpace != 3) {
-			if ($this->mpdf->PDFA && !$this->mpdf->PDFAauto) {
+		if (($this->mpdf->PDFA && $this->mpdf->restrictColorSpace != 3) || $this->mpdf->pdfxConvertsCmyk()) {
+			if (($this->mpdf->PDFA && !$this->mpdf->PDFAauto) || ($this->mpdf->PDFX && !$this->mpdf->PDFXauto)) {
 				$PDFAXwarnings[] = "CMYK color specified '" . $color . "' (converted to RGB)";
 			}
 			$c = $this->colorModeConverter->cmyk2rgb($c);
@@ -159,6 +172,11 @@ private function restrictCmykColorSpace($c, $color, &$PDFAXwarnings = [])
 	 */
 	private function restrictRgbaColorSpace($c, $color, &$PDFAXwarnings = [])
 	{
+		// PDF/X-4 keeps the transparency, which the colour space it settles on carries
+		if ($this->mpdf->isPdfx4()) {
+			return $this->restrictRgbColorSpace($c, $color, $PDFAXwarnings);
+		}
+
 		if ($this->mpdf->PDFX || ($this->mpdf->PDFA && $this->mpdf->restrictColorSpace == 3)) {
 			if (($this->mpdf->PDFA && !$this->mpdf->PDFAauto) || ($this->mpdf->PDFX && !$this->mpdf->PDFXauto)) {
 				$PDFAXwarnings[] = "RGB color with transparency specified '" . $color . "' (converted to CMYK" . ($this->mpdf->transparencyAllowed() ? ')' : ' without transparency)');
@@ -179,6 +197,30 @@ private function restrictRgbaColorSpace($c, $color, &$PDFAXwarnings = [])
 		return $c;
 	}
 
+	/**
+	 * Tagging black sRGB would have the press make it out of all four inks, which fringes text where the
+	 * plates are a hair out of register. A neutral colour goes to DeviceGray instead, which ISO 15930-7
+	 * permits where the output condition is CMYK or grey, and which such a condition takes as its black
+	 * separation. A colour that is neutral but translucent keeps its RGB, since DeviceGray carries no
+	 * alpha for mPDF to put it back into.
+	 *
+	 * @param float[] $c A colour in RGB or RGBA
+	 *
+	 * @return float[]|null That colour in DeviceGray, or null where it is not neutral and opaque
+	 */
+	private function neutralToGray($c)
+	{
+		if ($c[1] != $c[2] || $c[2] != $c[3]) {
+			return null;
+		}
+
+		if ($c[0] == 5 && $c[4] < 100) {
+			return null;
+		}
+
+		return [1, $c[1]];
+	}
+
 	/**
 	 * @param mixed $c
 	 * @param string $color
@@ -188,6 +230,10 @@ private function restrictRgbaColorSpace($c, $color, &$PDFAXwarnings = [])
 	 */
 	private function restrictCmykaColorSpace($c, $color, &$PDFAXwarnings = [])
 	{
+		if ($this->mpdf->isPdfx4()) {
+			return $this->restrictCmykColorSpace($c, $color, $PDFAXwarnings);
+		}
+
 		if ($this->mpdf->PDFA && $this->mpdf->restrictColorSpace != 3) {
 			if (!$this->mpdf->PDFAauto) {
 				$PDFAXwarnings[] = "CMYK color with transparency specified '" . $color . "' (converted to RGB" . ($this->mpdf->transparencyAllowed() ? ')' : ' without transparency)');

src/Config/ConfigVariables.php

@@ -154,12 +154,19 @@ public function __construct()
 			// 3 - allow CMYK / SPOT COLOR / Grayscale [convert RGB->CMYK]
 			'restrictColorSpace' => 0,
 
-			// PDFX/1-a Compliant files
-			// true=Forces compliance with PDFX-1a spec
+			// PDF/X Compliant files
+			// true=Forces compliance with the PDF/X version PDFXversion names
 			// Cannot be used with 'restrictColorSpace' (i.e. no RGB)
 			'PDFX' => false,
-			// Overrides warnings making changes when possible to force PDFX1-a compliance
+			// Overrides warnings making changes when possible to force PDF/X compliance
 			'PDFXauto' => false,
+			// The PDF/X version to write
+			//   4   PDF/X-4 (ISO 15930-7, PDF 1.6). The general choice for print, and the version print workflows
+			//       and the Ghent Workgroup specifications expect. Keeps transparency and layers, and prints to
+			//       the CMYK, RGB or grey condition ICCProfile names (SWOP where it names none)
+			//   1a  PDF/X-1a:2003 (ISO 15930-4, PDF 1.4). For printers and publications that accept only it:
+			//       CMYK and spot colour only, and translucent content is drawn opaque
+			'PDFXversion' => '4',
 
 			// PDF/A Compliant files
 			// true=Forces compliance with the PDF/A part and level PDFAversion names
@@ -183,7 +190,8 @@ public function __construct()
 
 			// Colour profile OutputIntent
 			// sRGB_IEC61966-2-1 (=default if blank and PDFA), or other added .icc profile
-			// Must be CMYK for PDFX, or appropriate type for PDFA(RGB or CMYK)
+			// Must be CMYK for PDF/X-1a, or appropriate type for PDFA(RGB or CMYK) or PDF/X-4
+			// PDF/X-4 embeds SWOP2006_Coated3v2 (CMYK) where blank. PDF/X takes a printer (prtr) profile only
 			'ICCProfile' => '',
 
 			'spotColors' => [],

src/Fonts/Color/ColorFormats.php

@@ -42,7 +42,8 @@ public static function drawable(array $fontFormats)
 	/**
 	 * Whether a document may draw colour fonts in colour: not where PDF/A-1b or PDF/X-1a forbid the
 	 * transparency every colour format is drawn with, nor where restrictColorSpace holds the document to
-	 * colours an RGB bitmap is not.
+	 * colours an RGB bitmap is not. PDF/X-4 allows the transparency, and its RGB is written calibrated
+	 * where the output intent is not RGB - see Type3FontWriter.
 	 *
 	 * Asked whenever it matters rather than once, since each of those settings can be changed on the
 	 * document after the fonts it starts with are added.
@@ -53,7 +54,7 @@ public static function drawable(array $fontFormats)
 	 */
 	public static function inColor(Mpdf $mpdf)
 	{
-		return !$mpdf->PDFA && !$mpdf->PDFX && !$mpdf->restrictColorSpace;
+		return !$mpdf->PDFA && !$mpdf->isPdfx1a() && !$mpdf->restrictColorSpace;
 	}
 
 	/**

src/Fonts/Color/FillsInColour.php

@@ -29,7 +29,7 @@ private function filled(array $colour, $fill, GlyphResources $resources)
 			$operators[] = $resources->alpha($alpha);
 		}
 		if ($rgb !== null) {
-			$operators[] = vsprintf('%.3F %.3F %.3F rg', $rgb);
+			$operators[] = $resources->rgb($rgb);
 		}
 
 		return $operators ? 'q ' . implode(' ', $operators) . "\n" . $fill . "\nQ\n" : $fill . "\n";