Add support for spot colors

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Unreleased
 
+- Add support for spot colors (#756, #1464)
 - Add support for PDF/A-1b, PDF/A-1a, PDF/A-2b, PDF/A-2a, PDF/A-3b, PDF/A-3a
 
 ### [v0.13.0] - 2021-10-24

docs/annotations.md

@@ -19,8 +19,10 @@ and some other properties. Here is a list of the available annotation methods:
 * `fileAnnotation(x, y, width, height, file, options)`
 
 Many of the annotations have a `color` option that you can specify. You can
-use an array of RGB values, a hex color, or a named CSS color value for that
-option.
+use an array of RGB values, a hex color, a named CSS color value, or a named 
+spot color value for that option.
+
+
 
 If you are adding an annotation to a piece of text, such as a link or
 underline, you will need to know the width and height of the text in order to
@@ -58,6 +60,12 @@ Here is an example that uses a few of the annotation types.
        .highlight(20, doc.y, doc.widthOfString('This text is highlighted!'), height)
        .text('This text is highlighted!');
 
+    // Create text with a spot color
+    doc.addSpotColor('PANTONE185C', 0, 100, 78, 9)
+    doc.moveDown()
+       .fillColor('PANTONE185C')
+       .text('This text uses spot color!');
+
     // Create the crossed out text
     doc.moveDown()
        .strike(20, doc.y, doc.widthOfString('STRIKE!'), height)

lib/mixins/SpotColor.js

@@ -0,0 +1,21 @@
+export default class SpotColor {
+  constructor(doc, name, C, M, Y, K) {
+    this.id = 'CS' + Object.keys(doc.spotColors).length;
+    this.name = name;
+    this.values = [C, M, Y, K];
+    this.ref = doc.ref([
+      'Separation',
+      this.name,
+      'DeviceCMYK',
+      {
+        Range: [0, 1, 0, 1, 0, 1, 0, 1],
+        C0: [0, 0, 0, 0],
+        C1: this.values.map(value => value / 100),
+        FunctionType: 2,
+        Domain: [0, 1],
+        N: 1
+      }
+    ]);
+    this.ref.end();
+  }
+}

lib/mixins/color.js

@@ -1,11 +1,13 @@
 import Gradient from '../gradient';
 import pattern from '../pattern';
+import SpotColor from './SpotColor';
 
 const { PDFGradient, PDFLinearGradient, PDFRadialGradient } = Gradient;
 const { PDFTilingPattern } = pattern;
 
 export default {
   initColor() {
+    this.spotColors = {};
     // The opacity dictionaries
     this._opacityRegistry = {};
     this._opacityCount = 0;
@@ -26,6 +28,8 @@ export default {
         color = [hex >> 16, (hex >> 8) & 0xff, hex & 0xff];
       } else if (namedColors[color]) {
         color = namedColors[color];
+      } else if (this.spotColors[color]) {
+        return this.spotColors[color];
       }
     }
 
@@ -66,8 +70,12 @@ export default {
     const space = this._getColorSpace(color);
     this._setColorSpace(space, stroke);
 
-    color = color.join(' ');
-    this.addContent(`${color} ${op}`);
+    if (color instanceof SpotColor) {
+      this.page.colorSpaces[color.id] = color.ref;
+      this.addContent(`1 ${op}`);
+    } else {
+      this.addContent(`${color.join(' ')} ${op}`);
+    }
 
     return true;
   },
@@ -78,6 +86,7 @@ export default {
   },
 
   _getColorSpace(color) {
+    if (color instanceof SpotColor) return color.id;
     return color.length === 4 ? 'DeviceCMYK' : 'DeviceRGB';
   },
 
@@ -163,6 +172,12 @@ export default {
 
   pattern(bbox, xStep, yStep, stream) {
     return new PDFTilingPattern(this, bbox, xStep, yStep, stream);
+  },
+
+  addSpotColor: function(name, C, M, Y, K) {
+    const color = new SpotColor(this, name, C, M, Y, K);
+    this.spotColors[name] = color;
+    return this;
   }
 };
 

lib/object.js

@@ -40,7 +40,7 @@ class PDFObject {
   static convert(object, encryptFn = null) {
     // String literals are converted to the PDF name type
     if (typeof object === 'string') {
-      return `/${object}`;
+      return /^[/[(\d].*/.test(object) ? object : `/${object}`
 
       // String objects are converted to PDF strings (UTF-16)
     } else if (object instanceof String) {

lib/page.js

@@ -157,6 +157,10 @@ class PDFPage {
 
   end() {
     this.dictionary.end();
+    this.resources.data.ColorSpace = this.resources.data.ColorSpace || {};
+    for (const color of Object.values(this.document.spotColors)) {
+      this.resources.data.ColorSpace[color.id] = `${color.ref.id} 0 R`;
+    }
     this.resources.end();
     return this.content.end();
   }

tests/unit/color.spec.js

@@ -35,4 +35,13 @@ describe('color', function() {
       1
     ]);
   });
+
+  test('normalize with spot color', function() {
+    const doc = new PDFDocument();
+    doc.addSpotColor('PANTONE 123 C', 0.1, 0.2, 0.3, 0.4);
+
+    const color = doc._normalizeColor('PANTONE 123 C');
+    expect(color.id).toEqual('CS0');
+    expect(color.values).toEqual([0.1, 0.2, 0.3, 0.4]);
+  });
 });

tests/unit/toContainChunk/index.js

@@ -1,4 +1,4 @@
-import diff from 'jest-diff';
+import { diff } from 'jest-diff';
 
 const buildMessage = (utils, data, chunk, headIndex) => {
   let message;