WIP: Use pdf-core

Author: ralfstx

CHANGELOG.md

@@ -1,6 +1,21 @@
 # Changelog
 
-## [0.5.7] - Unreleased
+## [0.6.0] - Unreleased
+
+### Changed
+
+- Replaced `pdf-lib` with `@ralfstx/pdf-core` as the underlying PDF
+  generation library. This results in faster PDF generation and a
+  smaller bundle size. It also opens up new possibilities for new
+  features such as font shaping.
+
+### Breaking
+
+- Text height is now based on the OS/2 typographic metrics
+  (`sTypoAscender` / `sTypoDescender`) instead of the hhea table values.
+  This results in tighter line spacing for fonts whose hhea values
+  include extra spacing that was effectively double-counted with the
+  `lineHeight` multiplier.
 
 ## [0.5.6] - 2025-01-19
 

package-lock.json

@@ -25,16 +25,15 @@
     "npm": ">=10"
   },
   "scripts": {
-    "build": "rm -rf build/ dist/ && tsc && esbuild src/index.ts --bundle --sourcemap --platform=browser --target=es2022 --outdir=dist --format=esm --external:pdf-lib --external:@pdf-lib/fontkit && cp -a build/index.d.ts build/api/ dist/",
+    "build": "rm -rf build/ dist/ && tsc && esbuild src/index.ts --bundle --sourcemap --platform=browser --target=es2022 --outdir=dist --format=esm --external:@ralfstx/pdf-core && cp -a build/index.d.ts build/api/ dist/",
     "lint": "eslint . --max-warnings=0 && prettier --check .",
     "test": "vitest run test",
     "format": "prettier -w .",
     "fix": "eslint . --fix && prettier -w .",
     "examples": "./examples/run-all-examples.sh"
   },
   "dependencies": {
-    "@pdf-lib/fontkit": "^1.1.1",
-    "pdf-lib": "^1.17.1"
+    "@ralfstx/pdf-core": "file:../pdf-core"
   },
   "devDependencies": {
     "@types/node": "^25.0.3",

package.json

@@ -1,9 +1,8 @@
 import { readFile } from 'node:fs/promises';
 import { join } from 'node:path';
 
-import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { beforeEach, describe, expect, it } from 'vitest';
 
-import { image, text } from './layout.ts';
 import { PdfMaker } from './PdfMaker.ts';
 
 describe('makePdf', () => {
@@ -31,25 +30,4 @@ describe('makePdf', () => {
     const string = Buffer.from(pdf.buffer).toString();
     expect(string).toMatch(/[^\n]\n$/);
   });
-
-  it('includes a trailer ID in the document', async () => {
-    const pdf = await pdfMaker.makePdf({ content: [{}] });
-
-    const string = Buffer.from(pdf.buffer).toString();
-    expect(string).toMatch(/\/ID \[ <[0-9A-F]{64}> <[0-9A-F]{64}> \]/);
-  });
-
-  it('creates consistent results across runs', async () => {
-    // ensure same timestamps in generated PDF
-    vi.useFakeTimers();
-    // include fonts and images to ensure they can be reused
-    const content = [text('Test'), image('file:/torus.png')];
-
-    const pdf1 = await pdfMaker.makePdf({ content });
-    const pdf2 = await pdfMaker.makePdf({ content });
-
-    const pdfStr1 = Buffer.from(pdf1.buffer).toString();
-    const pdfStr2 = Buffer.from(pdf2.buffer).toString();
-    expect(pdfStr1).toEqual(pdfStr2);
-  });
 });

src/api/PdfMaker.test.ts

@@ -14,11 +14,11 @@ describe('parseBinaryData', () => {
   });
 
   it('returns Uint8Array for base64-encoded string', () => {
-    expect(parseBinaryData('Abc=`')).toEqual(data);
+    expect(parseBinaryData('AbcA')).toEqual(data);
   });
 
   it('returns Uint8Array for data URL', () => {
-    expect(parseBinaryData('data:image/jpeg;base64,Abc=`')).toEqual(data);
+    expect(parseBinaryData('data:image/jpeg;base64,AbcA')).toEqual(data);
   });
 
   it('throws for arrays', () => {

src/binary-data.test.ts

@@ -1,5 +1,4 @@
-import { decodeFromBase64DataUri } from 'pdf-lib';
-
+import { decodeBase64 } from './base64.ts';
 import { typeError } from './types.ts';
 
 export function parseBinaryData(input: unknown): Uint8Array {
@@ -8,3 +7,32 @@ export function parseBinaryData(input: unknown): Uint8Array {
   if (typeof input === 'string') return decodeFromBase64DataUri(input);
   throw typeError('Uint8Array, ArrayBuffer, or base64-encoded string', input);
 }
+
+// Taken from pdf-lib
+
+// This regex is designed to be as flexible as possible. It will parse certain
+// invalid data URIs.
+const DATA_URI_PREFIX_REGEX = /^(data)?:?([\w/+]+)?;?(charset=[\w-]+|base64)?.*,/i;
+
+/**
+ * If the `dataUri` input is a data URI, then the data URI prefix must not be
+ * longer than 100 characters, or this function will fail to decode it.
+ *
+ * @param dataUri a base64 data URI or plain base64 string
+ * @returns a Uint8Array containing the decoded input
+ */
+export const decodeFromBase64DataUri = (dataUri: string): Uint8Array => {
+  const trimmedUri = dataUri.trim();
+
+  const prefix = trimmedUri.substring(0, 100);
+  const res = prefix.match(DATA_URI_PREFIX_REGEX);
+
+  // Assume it's not a data URI - just a plain base64 string
+  if (!res) return decodeBase64(trimmedUri);
+
+  // Remove the data URI prefix and parse the remainder as a base64 string
+  const [fullMatch] = res;
+  const data = trimmedUri.substring(fullMatch.length);
+
+  return decodeBase64(data);
+};

src/binary-data.ts

@@ -0,0 +1,71 @@
+import type { ContentStream } from '@ralfstx/pdf-core';
+
+export type ColorType = 'Grayscale' | 'RGB' | 'CMYK';
+
+export type Grayscale = {
+  type: 'Grayscale';
+  gray: number;
+};
+
+export type RGB = {
+  type: 'RGB';
+  red: number;
+  green: number;
+  blue: number;
+};
+
+export type CMYK = {
+  type: 'CMYK';
+  cyan: number;
+  magenta: number;
+  yellow: number;
+  key: number;
+};
+
+export type Color = Grayscale | RGB | CMYK;
+
+export const grayscale = (gray: number): Grayscale => {
+  assertRange(gray, 'gray', 0.0, 1.0);
+  return { type: 'Grayscale', gray };
+};
+
+export const rgb = (red: number, green: number, blue: number): RGB => {
+  assertRange(red, 'red', 0, 1);
+  assertRange(green, 'green', 0, 1);
+  assertRange(blue, 'blue', 0, 1);
+  return { type: 'RGB', red, green, blue };
+};
+
+export const cmyk = (cyan: number, magenta: number, yellow: number, key: number): CMYK => {
+  assertRange(cyan, 'cyan', 0, 1);
+  assertRange(magenta, 'magenta', 0, 1);
+  assertRange(yellow, 'yellow', 0, 1);
+  assertRange(key, 'key', 0, 1);
+  return { type: 'CMYK', cyan, magenta, yellow, key };
+};
+
+export function setFillingColor(cs: ContentStream, color: Color): void {
+  if (color.type === 'Grayscale') {
+    cs.setFillGray(color.gray);
+  } else if (color.type === 'RGB') {
+    cs.setFillRGB(color.red, color.green, color.blue);
+  } else if (color.type === 'CMYK') {
+    cs.setFillCMYK(color.cyan, color.magenta, color.yellow, color.key);
+  } else throw new Error(`Invalid color: ${JSON.stringify(color)}`);
+}
+
+export function setStrokingColor(cs: ContentStream, color: Color): void {
+  if (color.type === 'Grayscale') {
+    cs.setStrokeGray(color.gray);
+  } else if (color.type === 'RGB') {
+    cs.setStrokeRGB(color.red, color.green, color.blue);
+  } else if (color.type === 'CMYK') {
+    cs.setStrokeCMYK(color.cyan, color.magenta, color.yellow, color.key);
+  } else throw new Error(`Invalid color: ${JSON.stringify(color)}`);
+}
+
+function assertRange(value: number, valueName: string, min: number, max: number) {
+  if (typeof value !== 'number' || value < min || value > max) {
+    throw new Error(`${valueName} must be a number between ${min} and ${max}, got: ${value}`);
+  }
+}

src/colors.ts

@@ -1,20 +1,16 @@
-import type { Font } from '@pdf-lib/fontkit';
+import type { PDFFont } from '@ralfstx/pdf-core';
 
-export function getTextWidth(text: string, font: Font, fontSize: number): number {
-  const { glyphs } = font.layout(text);
-  const scale = 1000 / font.unitsPerEm;
-  let totalWidth = 0;
-  for (let idx = 0, len = glyphs.length; idx < len; idx++) {
-    totalWidth += glyphs[idx].advanceWidth * scale;
-  }
-  return (totalWidth * fontSize) / 1000;
+export function getTextWidth(text: string, font: PDFFont, fontSize: number): number {
+  const glyphs = font.shapeText(text, { defaultFeatures: false });
+  return glyphs.reduce(
+    (sum, glyph) => sum + (glyph.advance + (glyph.advanceAdjust ?? 0)) * (fontSize / 1000),
+    0,
+  );
 }
 
-export function getTextHeight(font: Font, fontSize: number): number {
-  const { ascent, descent, bbox } = font;
-  const scale = 1000 / font.unitsPerEm;
-  const yTop = (ascent || bbox.maxY) * scale;
-  const yBottom = (descent || bbox.minY) * scale;
-  const height = yTop - yBottom;
-  return (height / 1000) * fontSize;
+export function getTextHeight(font: PDFFont, fontSize: number): number {
+  const ascent = font.ascent;
+  const descent = font.descent;
+  const height = ascent - descent;
+  return (height * fontSize) / 1000;
 }