zcatpdf - PDF Generation Library for Zig

A pure Zig library for creating PDF documents with minimal dependencies.

const zcatpdf = @import("zcatpdf");

pub fn main() !void {
    var pdf = zcatpdf.Pdf.init(allocator, .{});
    defer pdf.deinit();

    var page = try pdf.addPage(.{});
    try page.setFont(.helvetica_bold, 24);
    try page.drawText(50, 750, "Hello, PDF!");

    try pdf.save("hello.pdf");
}

Features

• Pure Zig - Minimal dependencies (only libdeflate for compression)
• PDF 1.4 - Compatible with all PDF readers
• Complete text system - Fonts, alignment, word wrap, cells
• Images - JPEG and PNG (with alpha/transparency)
• Vector graphics - Lines, curves, shapes, gradients
• Tables - Helper for formatted tables
• Barcodes - Code128 (1D) and QR Code (2D)
• Links - Clickable URLs and internal page links
• Bookmarks - Document outline/navigation
• Transformations - Rotate, scale, translate, skew
• Transparency - Fill and stroke opacity
• Templates - Reusable document layouts
• Markdown - Styled text with Markdown syntax

Installation

Add zcatpdf to your build.zig.zon:

.dependencies = .{
    .zcatpdf = .{
        .url = "https://git.reugenio.com/reugenio/zcatpdf/archive/v1.0.tar.gz",
        .hash = "...",
    },
},

In your build.zig:

const zcatpdf_dep = b.dependency("zcatpdf", .{
    .target = target,
    .optimize = optimize,
});
exe.root_module.addImport("zcatpdf", zcatpdf_dep.module("zcatpdf"));

Quick Reference

Table of Contents

1. Document Creation
2. Pages
3. Text
4. Fonts
5. Colors
6. Graphics
7. Images
8. Tables
9. Links
10. Bookmarks
11. Barcodes
12. Transformations
13. Transparency
14. Gradients
15. Templates
16. Markdown
17. Compression

---

1. Document Creation

File: src/pdf.zig

const zcatpdf = @import("zcatpdf");

// Create document with default settings
var pdf = zcatpdf.Pdf.init(allocator, .{});
defer pdf.deinit();

// Create document with options
var pdf = zcatpdf.Pdf.init(allocator, .{
    .page_size = .a4,
    .orientation = .portrait,
    .unit = .pt,
});

// Set metadata
pdf.setTitle("Document Title");
pdf.setAuthor("Author Name");
pdf.setSubject("Subject");
pdf.setKeywords("keyword1, keyword2");
pdf.setCreator("Application Name");

// Save to file
try pdf.save("output.pdf");

// Or get as bytes
const data = try pdf.output();
defer allocator.free(data);

Types

Type	File	Description
Pdf	src/pdf.zig	Main document struct
Config	src/pdf.zig	Document configuration

---

2. Pages

File: src/page.zig, src/objects/base.zig

// Add page with document defaults
var page = try pdf.addPage(.{});

// Add page with specific size
var page = try pdf.addPage(.{ .size = .letter });

// Add page with custom dimensions (points)
var page = try pdf.addPageCustom(612, 792);

// Page sizes available
.a3      // 842 x 1191 pt
.a4      // 595 x 842 pt
.a5      // 420 x 595 pt
.letter  // 612 x 792 pt
.legal   // 612 x 1008 pt

// Orientations
.portrait
.landscape

Types

Type	File	Description
Page	src/page.zig	Page struct with drawing methods
PageSize	src/objects/base.zig	Standard page sizes
Orientation	src/objects/base.zig	Portrait/Landscape

---

3. Text

File: src/page.zig

// Simple text at position
try page.drawText(x, y, "Hello World");

// Cell with border and background
try page.cell(width, height, "Text", Border.all, .center, true);

// Multi-line text with word wrap
try page.multiCell(width, line_height, long_text, Border.none, .left, false);

// Get/set cursor position
const x = page.getX();
const y = page.getY();
page.setXY(100, 500);

// Line break
page.ln(20); // Move down 20 points

Cell Parameters

try page.cell(
    width,      // f32 - Cell width
    height,     // f32 - Cell height
    text,       // []const u8 - Text content
    border,     // Border - Border style
    align,      // Align - Text alignment
    fill,       // bool - Fill background
);

Border Options

Border.none    // No border
Border.all     // All sides
Border.left    // Left only
Border.right   // Right only
Border.top     // Top only
Border.bottom  // Bottom only
// Combine with Border.combine()

Alignment

.left
.center
.right

---

4. Fonts

File: src/fonts/type1.zig, src/fonts/ttf.zig

// Set font
try page.setFont(.helvetica, 12);
try page.setFont(.helvetica_bold, 14);
try page.setFont(.times_roman, 11);
try page.setFont(.courier, 10);

// Calculate string width
const width = zcatpdf.Font.helvetica.stringWidth("Hello", 12.0);

Available Fonts (Type1 built-in)

Font	Constant
Helvetica	.helvetica
Helvetica Bold	.helvetica_bold
Helvetica Oblique	.helvetica_oblique
Helvetica Bold Oblique	.helvetica_bold_oblique
Times Roman	.times_roman
Times Bold	.times_bold
Times Italic	.times_italic
Times Bold Italic	.times_bold_italic
Courier	.courier
Courier Bold	.courier_bold
Courier Oblique	.courier_oblique
Courier Bold Oblique	.courier_bold_oblique
Symbol	.symbol
ZapfDingbats	.zapf_dingbats

TrueType Fonts (parsing only)

// Load TTF file
const font_data = try std.fs.cwd().readFileAlloc(allocator, "font.ttf", 10_000_000);
var ttf = try zcatpdf.TrueTypeFont.parse(allocator, font_data);
defer ttf.deinit();

// Get font info
std.debug.print("Family: {s}\n", .{ttf.family_name});
std.debug.print("Ascender: {d}\n", .{ttf.ascender});

// Calculate string width
const width = ttf.stringWidth("Hello", 12.0);

Types

Type	File	Description
Font	src/fonts/type1.zig	Type1 font enum
TrueTypeFont	src/fonts/ttf.zig	TTF parser

---

5. Colors

File: src/graphics/color.zig

// Set colors
page.setFillColor(zcatpdf.Color.red);
page.setStrokeColor(zcatpdf.Color.blue);

// RGB (0-255)
page.setFillColor(zcatpdf.Color.rgb(255, 128, 0));

// Hex
page.setFillColor(zcatpdf.Color.hex(0xFF8000));

// Grayscale (0.0-1.0)
page.setFillColor(zcatpdf.Color.gray(0.5));

// CMYK (0.0-1.0)
page.setFillColor(zcatpdf.Color.cmyk(0, 1, 1, 0)); // Red

Predefined Colors

Color.black
Color.white
Color.red
Color.green
Color.blue
Color.yellow
Color.cyan
Color.magenta
Color.orange
Color.purple
Color.pink
Color.brown
Color.gray
Color.light_gray
Color.dark_gray

Types

Type	File	Description
Color	src/graphics/color.zig	Color struct (RGB, CMYK, Gray)

---

6. Graphics

File: src/page.zig, src/content_stream.zig

Lines

try page.setLineWidth(2.0);
try page.drawLine(x1, y1, x2, y2);

Rectangles

// Stroke only
try page.drawRect(x, y, width, height);

// Fill only
try page.fillRect(x, y, width, height);

// Fill and stroke
try page.fillAndStrokeRect(x, y, width, height);

Circles and Ellipses

// Circle
try page.drawCircle(cx, cy, radius);
try page.fillCircle(cx, cy, radius);

// Ellipse
try page.drawEllipse(cx, cy, rx, ry);
try page.fillEllipse(cx, cy, rx, ry);

// Arc
try page.drawArc(cx, cy, rx, ry, start_angle, end_angle);

Bezier Curves

// Cubic Bezier
try page.drawBezier(x0, y0, x1, y1, x2, y2, x3, y3);

// Quadratic Bezier
try page.drawQuadBezier(x0, y0, x1, y1, x2, y2);

Line Style

try page.setLineWidth(2.0);
try page.setLineCap(.round);   // .butt, .round, .square
try page.setLineJoin(.round);  // .miter, .round, .bevel
try page.setDashPattern(&.{5, 3}, 0); // [dash, gap], phase

Types

Type	File	Description
ContentStream	src/content_stream.zig	Low-level PDF operators
LineCap	src/content_stream.zig	Line cap styles
LineJoin	src/content_stream.zig	Line join styles

---

7. Images

File: src/images/jpeg.zig, src/images/png.zig, src/images/image_info.zig

// Load JPEG
const jpeg_idx = try pdf.addJpegImageFromFile("photo.jpg");

// Load PNG
const png_idx = try pdf.addPngImageFromFile("logo.png");

// Load from memory
const img_idx = try pdf.addJpegImage(jpeg_bytes);
const img_idx = try pdf.addPngImage(png_bytes);

// Get image info
const info = pdf.getImage(img_idx).?;
std.debug.print("Size: {d}x{d}\n", .{info.width, info.height});

// Draw image at position with size
try page.image(img_idx, info, x, y, width, height);

// Draw image preserving aspect ratio
try page.imageFit(img_idx, info, x, y, max_width, max_height);

Supported Formats

Format	Features
JPEG	RGB, Grayscale
PNG	RGB, RGBA (with alpha), Grayscale, Indexed

Types

Type	File	Description
ImageInfo	src/images/image_info.zig	Image metadata
ImageFormat	src/images/image_info.zig	JPEG, PNG enum

---

8. Tables

File: src/table.zig

const col_widths = [_]f32{ 200, 100, 100, 100 };

var table = zcatpdf.Table.init(page, .{
    .x = 50,
    .y = 700,
    .col_widths = &col_widths,
    .row_height = 20,
    .header_bg_color = zcatpdf.Color.hex(0xE0E0E0),
    .border = true,
});

// Header row
try table.header(&.{ "Description", "Qty", "Price", "Total" });

// Data rows
try table.row(&.{ "Product A", "2", "$10.00", "$20.00" });
try table.row(&.{ "Product B", "1", "$25.00", "$25.00" });

// Footer row
try table.footer(&.{ "", "", "Total:", "$45.00" });

Table Options

TableOptions{
    .x = 50,                           // X position
    .y = 700,                          // Y position
    .col_widths = &widths,             // Column widths array
    .row_height = 20,                  // Row height
    .header_bg_color = Color.gray,     // Header background
    .row_bg_color = null,              // Row background
    .alt_row_bg_color = null,          // Alternating row background
    .border = true,                    // Draw borders
    .header_font = .helvetica_bold,    // Header font
    .body_font = .helvetica,           // Body font
    .font_size = 10,                   // Font size
}

Types

Type	File	Description
Table	src/table.zig	Table helper
TableOptions	src/table.zig	Table configuration

---

9. Links

File: src/links.zig, src/page.zig

// URL link with visual styling (blue + underline)
_ = try page.urlLink(x, y, "Click here", "https://example.com");

// URL link from current position
_ = try page.writeUrlLink("Visit website", "https://example.com");

// Internal link (jump to page)
try page.addInternalLink(target_page, x, y, width, height);

// URL link without visual (just annotation)
try page.addUrlLink("https://example.com", x, y, width, height);

Types

Type	File	Description
Link	src/links.zig	Link struct
PageLinks	src/links.zig	Page link collection

---

10. Bookmarks

File: src/outline.zig

// Add bookmark to page
try pdf.addBookmark("Chapter 1", 0);  // page index 0

// Add bookmark with Y position
try pdf.addBookmarkAt("Section 1.1", 0, 500);

Bookmarks appear in the PDF reader's sidebar for navigation.

Types

Type	File	Description
Outline	src/outline.zig	Document outline
OutlineItem	src/outline.zig	Single bookmark

---

11. Barcodes

File: src/barcodes/code128.zig, src/barcodes/qr.zig

Code128 (1D)

// Basic barcode
try page.drawCode128(x, y, "ABC-12345", height, module_width);

// Barcode with text below
try page.drawCode128WithText(x, y, "ABC-12345", height, module_width, show_text);

QR Code (2D)

try page.drawQRCode(x, y, "https://example.com", size, error_correction);

// Error correction levels
zcatpdf.QRCode.ErrorCorrection.L  // 7% recovery
zcatpdf.QRCode.ErrorCorrection.M  // 15% recovery
zcatpdf.QRCode.ErrorCorrection.Q  // 25% recovery
zcatpdf.QRCode.ErrorCorrection.H  // 30% recovery

Types

Type	File	Description
Code128	src/barcodes/code128.zig	Code128 encoder
QRCode	src/barcodes/qr.zig	QR Code encoder

---

12. Transformations

File: src/page.zig

// Save state before transforming
try page.saveState();

// Rotate around point (degrees)
try page.rotate(45, center_x, center_y);

// Scale from point
try page.scale(2.0, 1.5, origin_x, origin_y);

// Translate
try page.translate(100, 50);

// Skew (degrees)
try page.skew(15, 0);  // X skew
try page.skew(0, 10);  // Y skew

// Custom transformation matrix
try page.transform(a, b, c, d, e, f);

// Restore state
try page.restoreState();

Important: Always use saveState()/restoreState() to limit transformation scope.

---

13. Transparency

File: src/graphics/extgstate.zig, src/page.zig

// Set fill opacity (0.0 = transparent, 1.0 = opaque)
try page.setFillOpacity(0.5);

// Set stroke opacity
try page.setStrokeOpacity(0.75);

// Set both at once
try page.setOpacity(0.3);

// Reset to fully opaque
try page.setOpacity(1.0);

Types

Type	File	Description
ExtGState	src/graphics/extgstate.zig	Extended graphics state

---

14. Gradients

File: src/graphics/gradient.zig, src/page.zig

Linear Gradients

// Horizontal gradient
try page.linearGradientRect(x, y, width, height,
    zcatpdf.Color.red, zcatpdf.Color.blue, .horizontal);

// Vertical gradient
try page.linearGradientRect(x, y, width, height,
    zcatpdf.Color.green, zcatpdf.Color.yellow, .vertical);

// Diagonal gradient
try page.linearGradientRect(x, y, width, height,
    zcatpdf.Color.purple, zcatpdf.Color.cyan, .diagonal);

Radial Gradients

// Circle gradient (center to edge)
try page.radialGradientCircle(cx, cy, radius,
    zcatpdf.Color.white, zcatpdf.Color.blue);

// Ellipse gradient
try page.radialGradientEllipse(cx, cy, rx, ry,
    zcatpdf.Color.yellow, zcatpdf.Color.red);

Types

Type	File	Description
Gradient	src/graphics/gradient.zig	Gradient definitions
LinearGradient	src/graphics/gradient.zig	Linear gradient
RadialGradient	src/graphics/gradient.zig	Radial gradient
GradientDirection	src/page.zig	horizontal, vertical, diagonal

---

15. Templates

File: src/template/template.zig

Templates define reusable document layouts with named regions.

// Use predefined invoice template
var tmpl = try zcatpdf.Template.invoiceTemplate(allocator);
defer tmpl.deinit();

// Or create custom template
var tmpl = zcatpdf.Template.init(allocator, "custom", 595, 842);
defer tmpl.deinit();

try tmpl.defineRegion("header", .{
    .x = 50,
    .y = 750,
    .width = 495,
    .height = 80,
    .region_type = .text,
});

// Use regions to position content
if (tmpl.getRegion("header")) |region| {
    try page.drawText(region.x, region.y, "Header Content");
}

Predefined Templates

• Template.invoiceTemplate() - Invoice with header, customer, items, totals, footer
• Template.letterTemplate() - Letter with sender, recipient, date, subject, body, signature

Types

Type	File	Description
Template	src/template/template.zig	Template struct
TemplateRegion	src/template/template.zig	Region definition
RegionType	src/template/template.zig	text, image, table, custom
FixedContent	src/template/template.zig	Repeating content

---

16. Markdown

File: src/markdown/markdown.zig

Parse Markdown-style text and render with appropriate styles.

var renderer = zcatpdf.MarkdownRenderer.init(allocator);
defer renderer.deinit();

try renderer.parse(
    \\# Heading 1
    \\
    \\This is **bold** and *italic* text.
    \\
    \\- Bullet item
    \\- Another item
    \\
    \\[Link text](https://example.com)
);

// Render to PDF
for (renderer.getLines()) |line| {
    for (line.spans) |span| {
        const font = zcatpdf.MarkdownRenderer.fontForStyle(span.style);
        try page.setFont(font, span.font_size orelse 12);

        if (span.color) |color| {
            page.setFillColor(zcatpdf.Color.hex(color));
        }

        try page.drawText(x, y, span.text);
        x += font.stringWidth(span.text, font_size);
    }
    y -= line_height;
}

Supported Syntax

Syntax	Result
**text** or __text__	Bold
*text* or _text_	Italic
***text***	Bold + Italic
~~text~~	Strikethrough
[text](url)	Link
# Heading	Heading 1
## Heading	Heading 2
### Heading	Heading 3
- item	Bullet list
1. item	Numbered list

Types

Type	File	Description
MarkdownRenderer	src/markdown/markdown.zig	Parser/renderer
TextSpan	src/markdown/markdown.zig	Styled text span
SpanStyle	src/markdown/markdown.zig	Style flags

---

17. Compression

File: src/compression/zlib.zig, src/output/producer.zig

// Configure compression when creating document
var pdf = zcatpdf.Pdf.init(allocator, .{
    .compression = .{
        .enabled = true,
        .level = 6,        // 0-12, higher = better compression
        .min_size = 256,   // Don't compress streams smaller than this
    },
});

Compression Options

Option	Default	Description
enabled	true	Enable FlateDecode compression
level	6	Compression level (0-12)
min_size	256	Minimum stream size to compress

Types

Type	File	Description
CompressionOptions	src/output/producer.zig	Compression config

---

File Structure

src/
├── root.zig              # Public exports
├── pdf.zig               # Pdf document facade
├── page.zig              # Page with drawing methods
├── content_stream.zig    # PDF operators
├── table.zig             # Table helper
├── pagination.zig        # Page numbers, headers, footers
├── links.zig             # Link types
├── outline.zig           # Bookmarks
├── fonts/
│   ├── mod.zig           # Font exports
│   ├── type1.zig         # 14 Type1 fonts + metrics
│   └── ttf.zig           # TrueType parser
├── graphics/
│   ├── mod.zig           # Graphics exports
│   ├── color.zig         # Color types
│   ├── extgstate.zig     # Transparency (ExtGState)
│   └── gradient.zig      # Linear/Radial gradients
├── images/
│   ├── mod.zig           # Image exports
│   ├── image_info.zig    # ImageInfo struct
│   ├── jpeg.zig          # JPEG parser
│   └── png.zig           # PNG parser
├── barcodes/
│   ├── mod.zig           # Barcode exports
│   ├── code128.zig       # Code128 encoder
│   └── qr.zig            # QR Code encoder
├── compression/
│   ├── mod.zig           # Compression exports
│   └── zlib.zig          # libdeflate wrapper
├── objects/
│   ├── mod.zig           # Object exports
│   └── base.zig          # PageSize, Orientation
├── output/
│   ├── mod.zig           # Output exports
│   └── producer.zig      # PDF serialization
├── security/
│   ├── mod.zig           # Security exports
│   ├── rc4.zig           # RC4 cipher
│   └── encryption.zig    # PDF encryption
├── forms/
│   ├── mod.zig           # Forms exports
│   └── field.zig         # TextField, CheckBox
├── svg/
│   ├── mod.zig           # SVG exports
│   └── parser.zig        # SVG parser
├── template/
│   ├── mod.zig           # Template exports
│   └── template.zig      # Template definitions
└── markdown/
    ├── mod.zig           # Markdown exports
    └── markdown.zig      # Markdown parser

---

Examples

16 example files in examples/:

File	Description
hello.zig	Minimal PDF
invoice.zig	Complete invoice
text_demo.zig	Text system (cell, multiCell)
image_demo.zig	JPEG and PNG images
table_demo.zig	Table helper
pagination_demo.zig	Multi-page with page numbers
links_demo.zig	Clickable links
bookmarks_demo.zig	Document outline
curves_demo.zig	Bezier, circles, arcs
transforms_demo.zig	Rotate, scale, skew
transparency_demo.zig	Opacity/alpha
gradient_demo.zig	Linear and radial gradients
barcode_demo.zig	Code128 and QR codes
ttf_demo.zig	TrueType font parsing
template_demo.zig	Document templates
markdown_demo.zig	Markdown styled text

Run Examples

# Build all
zig build

# Run specific example
./zig-out/bin/hello
./zig-out/bin/invoice
./zig-out/bin/barcode_demo
# etc.

---

Known Limitations

• TTF Font Subsetting: When embedding TrueType fonts, the entire font file is included rather than just the glyphs used. This can result in larger PDF files when using custom fonts. Font subsetting is planned for a future version.

---

Building

# Build library
zig build

# Run tests
zig build test

# Build specific example
zig build hello

---

License

MIT

---

Version

v1.0 - Feature Complete (2025-12-09)