SkiaSharp.QrCode

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SkiaSharp.QrCode

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High-performance QR code generator/reader with SkiaSharp integration.

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# SkiaSharp.QrCode

[Migration](docs/migration.md) | [Data Capacity](docs/data-capacity.md) | [Design Docs](.github/docs)

SkiaSharp.QrCode provides high-performance QR code generation/read with [SkiaSharp](https://github.com/mono/SkiaSharp) integration.

![Performance Benchmark](https://raw.githubusercontent.com/guitarrapc/SkiaSharp.QrCode/main/assets/benchmark_simpleencode_net10.0.png)

> Benchmark results comparing SkiaSharp.QrCode with other libraries. See [src/SkiaSharp.QrCode.Benchmark](src/SkiaSharp.QrCode.Benchmark) for details. Above results are generated on .NET 10 with AMD Ryzen 9 7950X3D CPU, with GFNI and AVX2 enabled.

Many existing QR code libraries rely on System.Drawing, which has well-known GDI+ limitations and cross-platform issues. SkiaSharp.QrCode was created to provide high performance, minimum memory allocation, a simpler and more intuitive API while leveraging SkiaSharp's cross-platform capabilities. Generate a QR code in a single line, or customize every detail - the choice is yours.

You can create professional-looking QR codes like this with just a few lines of code. Here's a small sample of Standard QR, Micro QR and rMQR.

See [samples/ConsoleApp](samples/ConsoleApp) for code examples generating these styles.

## Playground

Try SkiaSharp.QrCode in your browser, no install required: **[SkiaSharp.QrCode Playground](https://guitarrapc.github.io/SkiaSharp.QrCode/)**

The playground runs the actual library compiled to WebAssembly (GitHub Pages, fully static). Tune gradients, module shapes, finder patterns and logos in realtime, then download the PNG or SVG, or share your settings as a permalink. Every generated code is decoded back in-browser by the library's own decoder as a self-check, and the *Decode an image* panel reads QR codes from your own image files. Source lives in [src/SkiaSharp.QrCode.Playground](src/SkiaSharp.QrCode.Playground); it is deployed to GitHub Pages by [release.yaml](.github/workflows/release.yaml) as part of every release.

## Overview

SkiaSharp.QrCode is a modern, high-performance QR code generation library built on SkiaSharp. SkiaSharp.QrCode allocates memory only for the actual QR code data, with zero additional allocations during processing.

- **Simple API**: One-liner QR code generation with sensible defaults
- **High Performance**: Optimal speed and minimum memory allocation
- **Highly Customizable**: Gradients, icons, custom shapes, colors, and more
- **Raster & Vector Output**: PNG, JPEG, WebP, and SVG (scales without quality loss)
- **Cross-Platform**: Windows, Linux, macOS, iOS, Android, WebAssembly
- **Zero Dependencies**: QR generation without external libraries (SkiaSharp for rendering only)
- **No System.Drawing**: Avoids GDI+ issues and Windows dependencies
- **NativeAOT Ready**: Full support for .NET Native AOT compilation
- **Modern .NET**: .NET Standard 2.0, 2.1, .NET 8+

## Supported Symbologies

SkiaSharp.QrCode implements the Standard QR Code symbology, Micro QR generation/decoding, and rMQR generation/decoding. Unless a section says otherwise, this README refers to Standard QR; Micro QR is available via `MicroQRCodeGenerator` / `MicroQRCodeDecoder`, rMQR via `RmQRCodeGenerator` / `RmQRCodeImageBuilder` / `RmQRCodeDecoder`.

| Symbology | Standard | Generate (Encode) | Decode |
|---|---|---|---|
| Standard QR (versions 1–40) | ISO/IEC 18004 | ✅ | ✅ |
| Micro QR (M1–M4) | ISO/IEC 18004 | ✅ | ✅ |
| rMQR (R7x43–R17x139) | ISO/IEC 23941 | ✅ | ✅ |

See the [FAQ](#does-it-support-micro-qr-or-rmqr) for the Micro QR / rMQR status.

![StandardQR Performance](https://raw.githubusercontent.com/guitarrapc/SkiaSharp.QrCode/main/assets/benchmark_standardqr_encode.png)

![MicroQR Performance](https://raw.githubusercontent.com/guitarrapc/SkiaSharp.QrCode/main/assets/benchmark_microqr_encode.png)

## Installation

Visit [SkiaSharp.QrCode on NuGet.org](https://www.nuget.org/packages/SkiaSharp.QrCode)

```bash
dotnet add package SkiaSharp.QrCode
```

## Quick Start

### Simplest Example

Single line QR code generation:

```csharp
using SkiaSharp.QrCode.Image;

// one-liner save to file
File.WriteAllBytes("qrcode.png", QRCodeImageBuilder.GetPngBytes("Hello"));

// Or get bytes
var pngBytes = QRCodeImageBuilder.GetPngBytes("https://example.com");
```

### Common Use Cases

Generate QR Code for URL.

```csharp
var pngBytes = QRCodeImageBuilder.GetPngBytes("https://example.com");
File.WriteAllBytes("qrcode.png", pngBytes);
```

WiFi QR Code.

```csharp
var wifiString = "WIFI:T:WPA;S:MyNetwork;P:MyPassword;;";
File.WriteAllBytes("wifi-qr.png", QRCodeImageBuilder.GetPngBytes(wifiString));
```

SVG (vector) output.

```csharp
File.WriteAllText("qrcode.svg", QRCodeImageBuilder.GetSvgString("https://example.com"));
```

Generate with Custom Settings.

```csharp
var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(512, 512)
    .WithErrorCorrection(ECCLevel.H)
    .ToByteArray();
```

Save Directly to Stream

```csharp
using SkiaSharp.QrCode.Image;

using var stream = File.OpenWrite("qrcode.png");
QRCodeImageBuilder.SavePng("Your content here", stream, ECCLevel.M, size: 512);
```

## Migration

See [Migration Guide](docs/migration.md) for details on migrating from older versions of SkiaSharp.QrCode.

## API Overview

SkiaSharp.QrCode provides three main APIs for generation, plus `QRCodeDecoder` for decoding.

**Recommendation**: Start with `QRCodeImageBuilder` for most scenarios. Use `QRCodeRenderer` when you need canvas control. Use `QRCodeGenerator` only for custom rendering implementations. Use `QRCodeDecoder` to read QR codes back (round-trip validation, decoding rendered images).

| Feature | QRCodeImageBuilder | QRCodeRenderer | QRCodeGenerator |
| --- | --- | --- | --- |
| Ease of use | High | Medium | Low |
| Flexibility | Medium | High | Highest |
| Built-in rendering | Yes | Yes | No |
| Custom canvas control | No | Yes | N/A |
| Recommended for beginners | Yes | No | No |

### QRCodeImageBuilder (Recommended)

Best for Most use cases - simple to advanced QR code generation. The high-level, fluent API for generating QR codes with minimal code. Provides a builder pattern with sensible defaults and extensive customization options.

**Key Features**:
- One-liner generation with `GetPngBytes()`, `SavePng()`, `SaveSvg()`
- Fluent API with `WithXxx()` methods
- Built-in support for colors, gradients, icons, shapes
- Multiple output formats (PNG, JPEG, WebP, SVG)
- Stream and byte array output

**When to use**:
- Quick QR code generation
- Standard customization needs
- File or stream output

**Example**:
```csharp
var pngBytes = QRCodeImageBuilder.GetPngBytes("content");
```

### QRCodeRenderer (Advanced)

Best for Custom rendering with full control over the canvas. The mid-level API that renders QR data onto an existing SkiaSharp canvas. Useful when you need to integrate QR codes into existing graphics or add custom post-processing.

**Key Features**:
- Render to existing `SKCanvas`
- Full control over rendering area (`SKRect`)
- Combine with other SkiaSharp drawing operations
- Custom effects and post-processing

**When to use**:
- Integrating QR codes into existing graphics
- Adding custom decorations or effects
- Multiple elements on the same canvas

**Example**:
```csharp
var qrData = QRCodeGenerator.CreateQrCode("content", ECCLevel.M);
var canvas = surface.Canvas;
QRCodeRenderer.Render(canvas, area, qrData, SKColors.Black, SKColors.White);
```

### QRCodeGenerator (Low-Level)

Best for QR data generation without rendering. The low-level API that generates raw QR code data (`QRCodeData`). Use this when you need the QR data structure itself, not the image.

**Key Features**:
- Generates `QRCodeData` (boolean module matrix stored as 1D byte array)
- Specify ECC level, ECI mode, quiet zone size
- No rendering logic included
- Smallest API surface

**When to use**:
- Custom rendering implementations
- Non-image output (e.g., ASCII art, LED displays)
- Maximum control over the rendering process

**Example**:
```csharp
var qrData = QRCodeGenerator.CreateQrCode("content", ECCLevel.M, quietZoneSize: 4);
// Use qrData for custom rendering
// Access individual modules: bool isDark = qrData[row, col];
```

#### Zero-Allocation Generation (Span destination)

For high-throughput scenarios (e.g., per-request QR generation on a web server), you can generate the module matrix into a caller-provided buffer with zero heap allocation. Calculate the required size with `GetRequiredBufferSize`, allocate (or rent) the buffer yourself, and pass it as `Span<byte>`:

```csharp
// 1. Calculate required buffer size (no allocation)
var calculated = QRCodeGenerator.GetRequiredBufferSize("content", ECCLevel.M, quietZoneSize: 4);

// 2. Allocate the buffer yourself (pool it, reuse it, or stackalloc it)
var buffer = ArrayPool<byte>.Shared.Rent(calculated.BufferSize);
try
{
 // 3. Generate directly into the buffer; returns bytes written (= QrSize * QrSize)
 var written = QRCodeGenerator.CreateQrCode("content", ECCLevel.M, buffer, quietZoneSize: 4);

// 4. Slice to the written region and consume
 var matrix = buffer.AsSpan(0, written);
 // One byte per module (0 = light, 1 = dark), row-major, quiet zone included:
 var isDark = matrix[row * calculated.QrSize + col] != 0;
}
finally
{
 ArrayPool<byte>.Shared.Return(buffer);
}
```

Buffer sizes are bounded: version 40 with the standard quiet zone needs 185 × 185 = 34,225 bytes, so a pooled or fixed buffer keeps memory usage constant regardless of request volume. Every byte of the written region is overwritten, so dirty pooled buffers are fine; bytes beyond the written region are left untouched.

### QRCodeDecoder (Decoding)

Decodes QR codes back into text, the inverse of `QRCodeGenerator`. Works at two levels:

- **Matrix level**: from `QRCodeData` or a byte-per-module span (the same format the zero-allocation generator produces). Full Reed-Solomon error correction included.
- **Image level**: from `SKBitmap` or a grayscale luminance span. Detects the QR code (arbitrary rotation, mirroring, inverted light-on-dark palettes and mild perspective supported), samples the grid, then decodes.

**Scope**: image decoding targets *clean* inputs, screenshots, rendered QR codes, and scans. Real-world photos with strong perspective, uneven lighting, or blur are out of scope; use a computer-vision grade reader such as ZXing.Net for those. See [Standard QR Decoder](.github/docs/specs/standardqr-decoder.md) for design details.

```csharp
// From QRCodeData (e.g. round-trip validation)
var qrData = QRCodeGenerator.CreateQrCode("content", ECCLevel.M);
if (QRCodeDecoder.TryDecode(qrData, out var text))
{
    Console.WriteLine(text); // "content"
}

// From an image
using var bitmap = SKBitmap.Decode("qr.png");
if (QRCodeDecoder.TryDecode(bitmap, out var text, out var info))
{
    Console.WriteLine($"{text} (version {info.Version}, ECC {info.EccLevel}, {info.ErrorsCorrected} errors corrected)");
}

// Zero-allocation: span in, span out
Span<char> destination = stackalloc char[QRCodeDecoder.GetMaxDecodedLength(version)];
if (QRCodeDecoder.TryDecode(moduleSpan, size, destination, out var written, out _))
{
 var text = destination.Slice(0, written); // no heap allocation
}
```

On failure, `QRCodeDecodeInfo.Status` explains why (`NotDetected`, `FormatInformationInvalid`, `DataUncorrectable`, `UnsupportedContent`, ...). Supported content: Numeric / Alphanumeric / Byte modes, ISO-8859-1 and UTF-8 (with or without ECI), versions 1-40, all ECC levels. Kanji mode, FNC1 and Structured Append are detected and reported as unsupported rather than misdecoded.

Micro QR symbols have their own decoder with the same shape (`MicroQRCodeData` / matrix / `SKBitmap` / zero-allocation span overloads):

```csharp
var micro = MicroQRCodeGenerator.CreateMicroQRCode("01234567", MicroQREccLevel.L);
if (MicroQRCodeDecoder.TryDecode(micro, out var text, out var info))
{
    Console.WriteLine($"{text} ({info.Version}, ECC {info.EccLevel})"); // 01234567 (M2, ECC L)
}

// Image scanning is explicitly typed, QRCodeDecoder stays Standard QR-only
using var bitmap = SKBitmap.Decode("microqr.png");
var found = MicroQRCodeDecoder.TryDecode(bitmap, out var scanned, out _);
```

Micro QR image detection targets clean, screen-rendered or scanned images, including arbitrary rotation, mirroring, inverted colors, uniform or non-uniform scaling, translation, and mild perspective distortion. Because Micro QR has only one finder pattern and no alignment patterns, its measured perspective envelope is intentionally more conservative than Standard QR: the test suite covers 2% top-edge inset for M1/M2 and 4% for M3/M4, including rotation and mirror combinations. Strong perspective, uneven lighting, and blur remain out of scope.

## Platform-Specific Considerations

### Linux Support

SkiaSharp requires native dependencies on Linux. You have two options:

#### Option 1: With Font Support (Recommended for text rendering)

Requires `libfontconfig1`:

```bash
sudo apt update && apt install -y libfontconfig1
```

```xml
<PackageReference Include="SkiaSharp.QrCode" Version="1.1.0" />
<PackageReference Include="SkiaSharp.NativeAssets.Linux" Version="4.148.0" />
```

#### Option 2: No Dependencies (QR code only)

If you don't need advanced font operations:

```xml
<PackageReference Include="SkiaSharp.QrCode" Version="1.1.0" />
<PackageReference Include="SkiaSharp.NativeAssets.Linux.NoDependencies" Version="4.148.0" />
```

> **Note**: `NoDependencies` can still draw text but cannot search fonts based on characters or use system fonts.
>
> See: [SkiaSharp Issue #964](https://github.com/mono/SkiaSharp/issues/964#issuecomment-549385484)

### NativeAOT Support

SkiaSharp.QrCode fully supports .NET NativeAOT. You need to include platform-specific native assets:

```xml
<PropertyGroup>
 <PublishAot>true</PublishAot>
 <PublishTrimmed>true</PublishTrimmed>
 <InvariantGlobalization>true</InvariantGlobalization>
</PropertyGroup>
```

> [!WARNING]
>  When using `PublishTrimmed`, ensure that your QR code content and rendering logic doesn't rely on reflection or dynamic code that might be trimmed.

#### Windows

```xml
<PackageReference Include="SkiaSharp.QrCode" Version="1.1.0" />
<PackageReference Include="SkiaSharp.NativeAssets.Win32" Version="4.148.0" />
```

#### Linux

```xml
<PackageReference Include="SkiaSharp.QrCode" Version="1.1.0" />
<PackageReference Include="SkiaSharp.NativeAssets.Linux.NoDependencies" Version="4.148.0" />
```

#### macOS

```xml
<PackageReference Include="SkiaSharp.QrCode" Version="1.1.0" />
<PackageReference Include="SkiaSharp.NativeAssets.macOS" Version="4.148.0" />
```

## Performance

SkiaSharp.QrCode is designed with performance as a top priority. The library minimizes memory allocations and maximizes throughput for QR code generation.

### Key Performance Characteristics

- **Minimal Memory Allocation**: Memory is only allocated for the final QR code data structure. The generation algorithm avoids intermediate allocations, resulting in minimal GC pressure.
- **Zero-Copy Rendering**: Direct rendering to SkiaSharp canvas without unnecessary buffer copies.
- **Optimized Encoding**: Efficient encoding mode selection and bit packing minimize QR code size and generation time.
- **Native Performance**: Leverages SkiaSharp's native rendering engine for maximum speed.

### Benchmark Results

Benchmark results show SkiaSharp.QrCode outperforming other popular .NET QR code libraries in both speed and memory usage.

- **Fastest Generation**: Outperforms other .NET QR code libraries in most scenarios
- **Lowest Memory Usage**: Minimal allocations reduce GC overhead
- **Consistent Performance**: Predictable performance across different QR code sizes and complexity

For detailed benchmark code and results, see the [src/SkiaSharp.QrCode.Benchmark](src/SkiaSharp.QrCode.Benchmark) directory.

## FAQ

### Why choose SkiaSharp.QrCode?

SkiaSharp offers several advantages for QR code generation:

- **Performance**: Native-level performance with hardware acceleration support
- **Cross-Platform**: Runs on Windows, Linux, macOS, iOS, Android, and WebAssembly
- **Modern .NET Support**: First-class support for .NET 6+ and .NET Core
- **No GDI+ Dependencies**: Avoids System.Drawing's Windows-specific issues
- **Rich Graphics API**: Advanced rendering capabilities (gradients, shapes, effects)
- **Active Development**: Well-maintained with regular updates

### Can I use this in ASP.NET Core?

Yes, SkiaSharp.QrCode works great in ASP.NET Core. SkiaSharp.QrCode also supports `IBufferWriter` for efficient memory usage.

```csharp
app.MapGet("/qr", (string url) =>
{
    var pngBytes = QRCodeImageBuilder.GetPngBytes(url);
    return Results.File(pngBytes, "image/png");
});

app.MapGet("/qr.svg", (string url) =>
{
    var svgBytes = QRCodeImageBuilder.GetSvgBytes(url);
    return Results.File(svgBytes, "image/svg+xml");
});
```

### Does it support Blazor WebAssembly?

Yes, SkiaSharp.QrCode works in Blazor WebAssembly & Pure WebAssembly.

- See the [samples/BlazorWasm](samples/BlazorWasm) folder for a Blazor WebAssembly example.
- See [src/SkiaSharp.QrCode.Playground](src/SkiaSharp.QrCode.Playground) for Pure WebAssembly usage.

### What about NativeAOT and trimming?

Yes, fully supported. See the [Platform-Specific Considerations](#platform-specific-considerations) section for details on required native assets.

### ISO-8859-2 and other encodings supports

Currently, SkiaSharp.QrCode supports ISO-8859-1 and UTF-8. Other encodings (e.g., ISO-8859-2, Shift JIS) are not supported at this time. This is mainly due to almost all QR code use cases being UTF-8 compatible nowadays. ISO-8859-2 and other legacy encodings are rarely used in practice.

| Supported | Encoding Mode | Encoding |
| --- | --- | --- |
| Supported | Numeric | ISO-8859-1 |
| Supported | Alphanumeric | ISO-8859-1 |
| Supported | Byte | UTF-8 |
| Not Supported | Kanji | Shift-JIS |

### Does SVG output require SkiaSharp.Svg or other packages?

No. SVG output uses `SKSvgCanvas` from the core SkiaSharp package, no additional dependencies. Note that SkiaSharp.QrCode outputs SVG only; it does not read or render existing SVG files.

### Any plan to support QR code scanning?

Yes. `QRCodeDecoder` decodes QR codes from module matrices and from images (see [API Overview](#qrcodedecoder-decoding)). Image decoding intentionally targets clean inputs: screenshots, rendered QR codes, and scans, including rotated and mirrored ones. Robust decoding of real-world photos (perspective distortion, uneven lighting, blur) is a computer-vision problem outside this library's scope, use a dedicated reader such as ZXing.Net for camera captures.

### Does it support Micro QR or rMQR?

Micro QR (M1–M4) is fully supported for generation and decoding. See [Micro QR](#supported-symbologies) for details.

rMQR (R7x43–R17x139, ISO/IEC 23941, rectangular symbols for narrow print lanes) is supported for generation and rendering via `RmQRCodeGenerator` and `RmQRCodeImageBuilder` (all 32 versions, ECC M/H, Numeric / Alphanumeric / Byte modes; Kanji is not implemented). Version selection is two-dimensional: pass an exact `RmQRVersion`, or let `RmQRFitStrategy` choose among the versions that fit (default `MinimizeArea`, the fewest modules, the same choice libzint and qrtool make automatically; note it can pick a taller, narrower symbol, e.g. 12 digits at M give R11x27 rather than the flatter R7x43), optionally within a fixed `RmQRHeight`. Rendering keeps the rectangular symbol's shape: `WithModulePixelSize` gives the exact matrix, `WithSize` letterboxes into the canvas (uniform module scale, never stretched), and `WithWidth` (the static helpers' `size`, default 512) sets the image width with the height following the symbol aspect ratio. `RmQRCodeDecoder` decodes rMQR module matrices (`RmQRCodeData` or byte-per-module spans with width and height, quiet zone stripped automatically) with per-block Reed-Solomon correction, and scans rMQR symbols from images (`SKBitmap` or a grayscale luminance span): clean, screen-rendered or scanned images with arbitrary rotation, mirroring, inverted colors, uniform or non-uniform scaling, translation and mild perspective (the test suite covers 2 % and 4 % keystone along either axis up to R17x139); `QRCodeDecoder` stays Standard QR-only. Capacities per version are listed in [docs/data-capacity.md](docs/data-capacity.md). See [rMQR](#rmqr) for examples.

### What QR code style provides the best scan reliability?

For optimal scan reliability, we recommend:

- **Use rectangular modules (default)**: Rectangle-shaped modules (`RectangleModuleShape`) provide the lowest error rate when scanning QR codes.
- **Avoid gaps between modules**: Using smaller module sizes or shapes like `Circle` or `RoundRect` creates gaps between modules, which increases scan error rates.
- **Use `ECCLevel.H` for non-standard styles**: If you need to use `Circle`, `RoundRect`, or other custom module shapes, we strongly recommend setting the error correction level to `ECCLevel.H` (High - 30% recovery capacity) to compensate for the reduced readability.
- **Always use `ECCLevel.H` with icons/logos**: When embedding icons or logos using `IconData`, `ECCLevel.H` is required to ensure the QR code remains scannable even when the center is partially obscured.

**Example:**

```csharp
// Best reliability - default settings with rectangular modules
var pngBytes = QRCodeImageBuilder.GetPngBytes("https://example.com");

// If using Circle or RoundRect - use High error correction
var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(800, 800)
    .WithErrorCorrection(ECCLevel.H) // Required for custom shapes
    .WithModuleShape(CircleModuleShape.Default);

// When using icons/logos - always use High error correction
using var logo = SKBitmap.Decode(File.ReadAllBytes("logo.png"));
var icon = IconData.FromImage(logo, iconSizePercent: 15);

var qrCodeWithIcon = new QRCodeImageBuilder("https://example.com")
    .WithSize(800, 800)
    .WithErrorCorrection(ECCLevel.H) // Required for icons
    .WithIcon(icon);
```

### How can I display QR codes in LINQPad?

Following shows how to display a QRCode inside a LINQPad Results pane.

```csharp
Bitmap.FromStream(new MemoryStream(QRCodeImageBuilder.GetPngBytes("WIFI:T:WPA;S:mynetwork;P:mypass;;"))).Dump();
```

## Standard QR Specifications

### ECC Level (Error Correction Levels)

QR codes support four levels of error correction, which allow the code to remain readable even when partially damaged or obscured:

| ECC Level | Error Correction Capability | Use Case |
|-----------|----------------------------|----------|
| **L (Low)** | ~7% recovery | Clean environments, maximum data capacity |
| **M (Medium)** | ~15% recovery | General purpose (default recommended) |
| **Q (Quartile)** | ~25% recovery | Outdoor use, moderate damage expected |
| **H (High)** | ~30% recovery | Required when adding logos/icons, harsh environments |

> **Tip**: Use ECC Level H when embedding icons in QR codes to ensure readability even when the center is obscured.

### Encoding Modes

QR codes support different encoding modes optimized for specific character types:

| Mode | Character Set | Bits per Character | Example |
|------|--------------|-------------------|---------|
| **Numeric** | 0-9 | ~3.3 bits | Phone numbers, postal codes |
| **Alphanumeric** | 0-9, A-Z, space, $ % * + - . / : | ~5.5 bits | URLs (uppercase), product codes |
| **Byte** | ISO-8859-1, UTF-8 | 8 bits | Text, URLs (mixed case), binary data |
| **Kanji** | Shift JIS characters | 13 bits | Japanese text |

> **Note**: The library automatically selects the most efficient encoding mode for your content.

### Version and Size

QR codes come in 40 versions (sizes), from Version 1 (21×21 modules) to Version 40 (177×177 modules). Each version adds 4 modules per side.

- **Version 1**: 21×21 modules
- **Version 2**: 25×25 modules
- ...
- **Version 40**: 177×177 modules

The library automatically selects the minimum version that can fit your content based on the selected ECC level.

See [Data Capacity Reference](docs/data-capacity.md) for practical capacities and full tables by version and ECC level.

## Usage Examples

Each symbology has its own API surface, see [Supported Symbologies](#supported-symbologies). Examples below are grouped by symbology.

### Standard QR

#### Using Builder Pattern

```csharp
using SkiaSharp.QrCode.Image;

var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(800, 800)
    .WithErrorCorrection(ECCLevel.H)
    .WithQuietZone(4);

var pngBytes = qrCode.ToByteArray();
File.WriteAllBytes("qrcode.png", pngBytes);
```

#### Direct File Output

```csharp
using SkiaSharp.QrCode.Image;
using var stream = File.OpenWrite("qrcode.png");

new QRCodeImageBuilder("https://example.com")
    .WithSize(1024, 1024)
    .WithErrorCorrection(ECCLevel.H)
    .SaveTo(stream);
```

#### Raster Output (PNG / JPEG / WebP)

Default format is PNG. Switch with `WithFormat()`, quality (0–100) applies to lossy formats (JPEG, WebP).

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

// PNG (default)
var pngBytes = new QRCodeImageBuilder("https://example.com")
    .WithSize(512, 512)
    .ToByteArray();

// JPEG
var jpegBytes = new QRCodeImageBuilder("https://example.com")
    .WithSize(512, 512)
    .WithFormat(SKEncodedImageFormat.Jpeg, quality: 90)
    .ToByteArray();

// WebP
var webpBytes = new QRCodeImageBuilder("https://example.com")
    .WithSize(512, 512)
    .WithFormat(SKEncodedImageFormat.Webp, quality: 80)
    .ToByteArray();

// Or one-liner helpers
var bytes = QRCodeImageBuilder.GetImageBytes(
    "https://example.com", SKEncodedImageFormat.Jpeg, ECCLevel.M, size: 512, quality: 90);
```

#### SVG Output (Vector)

SVG output draws the QR code as vector shapes, so it scales to any size without quality loss, ideal for print and web embedding. All builder options (colors, module shapes, gradients, finder patterns, icons) apply to SVG as well.

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

// One-liner: save to stream
using var stream = File.Create("qrcode.svg");
QRCodeImageBuilder.SaveSvg("https://example.com", stream);

// One-liner: SVG document string, e.g. for inline HTML embedding
var svg = QRCodeImageBuilder.GetSvgString("https://example.com");

// Builder: full styling support
var svgString = new QRCodeImageBuilder("https://example.com")
    .WithModulePixelSize(10)
    .WithErrorCorrection(ECCLevel.H)
    .WithColors(codeColor: SKColor.Parse("1B9CFC"))
    .ToSvgString(); // or SaveToSvg(stream) / SaveToSvg(bufferWriter) / GetSvgBytes(...)
```

Size options define the SVG viewport (in SVG units instead of pixels); `WithFormat()` does not apply to SVG output.

The root element always carries a `viewBox`, so the QR code scales its content when displayed at any size (`<img>`, CSS, or attribute-based sizing). Plain rectangular modules also get `shape-rendering="crispEdges"` to prevent antialiasing seams between modules; custom shapes (circles, rounded rects) keep antialiasing for smooth curves.

> [!TIP]
> Default rectangle modules produce compact SVG (horizontal module runs merge into single `<rect>` elements). Custom module shapes and gradients render correctly but produce larger documents, since each module becomes an individual vector element. Icon images are embedded as base64 data URIs.

#### Choosing Image Size

| Goal | API | Notes |
|---|---|---|
| Keep module edges sharp / logo aligned | `WithModulePixelSize(n)` | Output side = `QR matrix size * n`. Best default when using logos. |
| Also fit a fixed UI frame | `WithModulePixelSize(n)` + `WithSize(w, h)` | Canvas must be `>=` content size. Extra space is centered padding (`clearColor`). Too-small canvas throws. |
| Only need a fixed pixel box | `WithSize(w, h)` | Simple, but module size may become fractional when QR version changes. |

**Recommended (module-aligned):**

```csharp
using SkiaSharp.QrCode.Image;

var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithModulePixelSize(10) // content = (QR matrix size in modules) * 10
    .WithErrorCorrection(ECCLevel.H)
    .WithQuietZone(4);

var pngBytes = qrCode.ToByteArray();
```

**Recommended (module-aligned + fixed canvas):**

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithModulePixelSize(10)
    .WithSize(512, 512) // must be >= content size
    .WithColors(clearColor: SKColors.Transparent)
    .WithErrorCorrection(ECCLevel.H);

var pngBytes = qrCode.ToByteArray();
```

**Fixed box only (may use fractional module pixels):**

```csharp
using SkiaSharp.QrCode.Image;

var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(512, 512)
    .WithErrorCorrection(ECCLevel.H);

var pngBytes = qrCode.ToByteArray();
```

#### Request Version

"abc" can fit in Version 1, but we request Version 10 to show more dots. This can be useful for adding logo with short content.

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

new QRCodeImageBuilder("abc")
    .WithSize(512, 512)
    .WithVersion(10)
    .ToByteArray();
```

#### Custom Colors

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

new QRCodeImageBuilder("https://example.com")
    .WithSize(800, 800)
    .WithColors(
        codeColor: SKColor.Parse("#000080"),      // Navy
        backgroundColor: SKColor.Parse("#FFE4B5"), // Moccasin
        clearColor: SKColors.Transparent)
    .ToByteArray();
```

#### Gradient QR code

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

var gradient = new GradientOptions(
    [SKColors.Blue, SKColors.Purple, SKColors.Pink],
    GradientDirection.TopLeftToBottomRight,
    [0f, 0.5f, 1f]);

var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(800, 800)
    .WithErrorCorrection(ECCLevel.H)
    .WithGradient(gradient)
    .WithModuleShape(RoundedRectangleModuleShape.Default, sizePercent: 0.9f);

var pngBytes = qrCode.ToByteArray();
```

#### QR code with Logo (icon only)

Prefer module-based sizing so the logo sits on the QR grid. See [Choosing Image Size](#choosing-image-size).

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

using var logo = SKBitmap.Decode(File.ReadAllBytes("logo.png"));

// Percent/pixel sizing (existing)
var iconByPercent = IconData.FromImage(logo, iconSizePercent: 15, iconBorderWidth: 10);

// Module-based sizing (recommended with WithModulePixelSize)
var iconByModules = IconData.FromImageByModules(logo, iconSizeModules: 7, iconBorderModules: 1);

var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithModulePixelSize(12)
    // .WithSize(512, 512) // optional: larger canvas with centered padding
    .WithErrorCorrection(ECCLevel.H) // High ECC recommended for icons
    .WithIcon(iconByModules);

var pngBytes = qrCode.ToByteArray();
```

#### QR code with Logo (icon and text)

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

using var logo = SKBitmap.Decode(File.ReadAllBytes("logo.png"));
using var font = new SKFont
{
    Size = 18,
    Typeface = SKTypeface.FromFamilyName("sans-serif", SKFontStyle.Bold)
};
var icon = new IconData
{
    // Default text is placed below the icon image, centered
    Icon = new ImageTextIconShape(logo, "FooBar", SKColors.Black, font, textPadding: 2),
    IconSizePercent = 13,
    IconBorderWidth = 18,
};
var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(800, 800)
    .WithErrorCorrection(ECCLevel.H) // High ECC recommended for icons
    .WithIcon(icon);

var pngBytes = qrCode.ToByteArray();
```

#### Custom Module Shapes

```csharp
using SkiaSharp;
using SkiaSharp.QrCode.Image;

var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(800, 800)
    .WithModuleShape(CircleModuleShape.Default, sizePercent: 0.95f)
    .WithColors(codeColor: SKColors.DarkBlue);

var pngBytes = qrCode.ToByteArray();
```

#### Custom Finder Pattern

```csharp
var qrCode = new QRCodeImageBuilder("https://example.com")
    .WithSize(512, 512)
    .WithFinderPatternShape(RoundedRectangleFinderPatternShape.Default)
    .WithColors(codeColor: SKColors.DarkBlue);

var pngBytes = qrCode.ToByteArray();
```

#### Gradient QR Code

```csharp
var instagramGradient = new GradientOptions([
        SKColor.Parse("FCAF45"),  // Orange
        SKColor.Parse("F77737"),  // Orange-Red
        SKColor.Parse("E1306C"),  // Pink
        SKColor.Parse("C13584"),  // Purple
        SKColor.Parse("833AB4")   // Deep Purple
    ],
    GradientDirection.TopLeftToBottomRight,
    [0f, 0.25f, 0.5f, 0.75f, 1f]);

var qrCode = new QRCodeImageBuilder(content)
    .WithSize(512, 512)
    .WithColors(backgroundColor: SKColors.White, clearColor: SKColors.White)
    .WithModuleShape(CircleModuleShape.Default, sizePercent: 0.95f)
    .WithFinderPatternShape(RoundedRectangleCircleFinderPatternShape.Default)
    .WithGradient(instagramGradient);

var pngBytes = qrCode.ToByteArray();
```

#### Low-Level Canvas Rendering

For maximum control over rendering:

```csharp
using SkiaSharp;
using SkiaSharp.QrCode;

// Generate QR data
var qrData = QRCodeGenerator.CreateQrCode("https://example.com", ECCLevel.M, quietZoneSize: 4);

// Create canvas
var info = new SKImageInfo(800, 800);
using var surface = SKSurface.Create(info);
var canvas = surface.Canvas;

// Render QR code
canvas.Render(qrData, info.Width, info.Height);

// Save
using var image = surface.Snapshot();
using var data = image.Encode(SKEncodedImageFormat.Png, 100);
using var stream = File.OpenWrite("qrcode.png");
data.SaveTo(stream);
```

### Micro QR

`MicroQRCodeGenerator`, `MicroQRCodeImageBuilder`, and `MicroQRCodeDecoder`, version/ECC constraints and capacity in the [FAQ](#does-it-support-micro-qr-or-rmqr). Runnable samples: [ConsoleApp patterns 24–26](samples/ConsoleApp).

#### One-liner (PNG)

```csharp
using SkiaSharp.QrCode;
using SkiaSharp.QrCode.Image;

// ISO/IEC 18004 M2-L numeric example, auto-selects the smallest version that fits
var pngBytes = MicroQRCodeImageBuilder.GetPngBytes("01234567", MicroQREccLevel.L, size: 256);
File.WriteAllBytes("microqr.png", pngBytes);
```

#### Builder (colors, module shape, gradient)

```csharp
using SkiaSharp;
using SkiaSharp.QrCode;
using SkiaSharp.QrCode.Image;

var gradient = new GradientOptions(
    [SKColor.Parse("00B894"), SKColor.Parse("0984E3")],
    GradientDirection.TopLeftToBottomRight);

var pngBytes = new MicroQRCodeImageBuilder("SKU-42")
    .WithModulePixelSize(14)
    .WithErrorCorrection(MicroQREccLevel.M)
    .WithColors(codeColor: SKColor.Parse("2D3436"), backgroundColor: SKColors.White)
    .WithModuleShape(RoundedRectangleModuleShape.Default, sizePercent: 0.92f)
    .WithGradient(gradient)
    .ToByteArray();
```

#### Decode (matrix and image)

```csharp
using SkiaSharp;
using SkiaSharp.QrCode;

var micro = MicroQRCodeGenerator.CreateMicroQRCode("01234567", MicroQREccLevel.L);
if (MicroQRCodeDecoder.TryDecode(micro, out var text, out var info))
{
    Console.WriteLine($"{text} ({info.Version}, ECC {info.EccLevel})"); // 01234567 (M2, ECC L)
}

// Image scan, use MicroQRCodeDecoder (QRCodeDecoder is Standard QR-only)
using var bitmap = SKBitmap.Decode("microqr.png");
var ok = MicroQRCodeDecoder.TryDecode(bitmap, out var scanned, out _);
```

### rMQR

`RmQRCodeGenerator`, `RmQRCodeImageBuilder` and `RmQRCodeDecoder`; version/ECC/fit constraints in the [FAQ](#does-it-support-micro-qr-or-rmqr), capacities in [docs/data-capacity.md](docs/data-capacity.md). Runnable samples: [ConsoleApp patterns 27–29](samples/ConsoleApp).

#### One-liner (PNG)

```csharp
using SkiaSharp.QrCode;
using SkiaSharp.QrCode.Image;

// size is the image WIDTH; the height follows the symbol aspect ratio (default fit: fewest modules)
var pngBytes = RmQRCodeImageBuilder.GetPngBytes("https://example.com/r/12345", RmQREccLevel.M, size: 512);
File.WriteAllBytes("rmqr.png", pngBytes);
```

#### Builder (fixed height, fit strategy, styling)

```csharp
using SkiaSharp;
using SkiaSharp.QrCode;
using SkiaSharp.QrCode.Image;

// A label lane 9 modules high: the width is chosen automatically
var pngBytes = new RmQRCodeImageBuilder("https://example.com/r/12345")
    .WithHeight(RmQRHeight.H9)
    .WithErrorCorrection(RmQREccLevel.H)
    .WithModulePixelSize(12)
    .WithColors(codeColor: SKColor.Parse("2D3436"), backgroundColor: SKColors.White)
    .WithModuleShape(RoundedRectangleModuleShape.Default, sizePercent: 0.9f)
    .ToByteArray();

// The flattest symbol that fits, instead of the fewest modules
var flat = RmQRCodeGenerator.CreateRmQRCode("012345678901", RmQREccLevel.M, fitStrategy: RmQRFitStrategy.MinimizeHeight);
Console.WriteLine(flat.Version); // R7x43 (the default MinimizeArea picks R11x27: 297 modules vs 301)

// Exact version, zero-allocation span output (byte per module, row-major, quiet zone included)
var size = RmQRCodeGenerator.GetRequiredBufferSize("ABC123".AsSpan(), RmQREccLevel.M, RmQRVersion.R7x59);
Span<byte> modules = new byte[size.BufferSize];
RmQRCodeGenerator.CreateRmQRCode("ABC123".AsSpan(), RmQREccLevel.M, modules, RmQRVersion.R7x59); // size.Width × size.Height
```

#### Decode (matrix and image)

```csharp
using SkiaSharp.QrCode;

var rmqr = RmQRCodeGenerator.CreateRmQRCode("012345678901", RmQREccLevel.M);
if (RmQRCodeDecoder.TryDecode(rmqr, out var text, out var info))
{
    Console.WriteLine($"{text} ({info.Version}, ECC {info.EccLevel}, {info.ErrorsCorrected} corrections)"); // 012345678901 (R11x27, ECC M, 0 corrections)
}

// Byte-per-module matrix with width and height (any light quiet zone is stripped automatically);
// zero-allocation variant with a caller-provided destination
var size = RmQRCodeGenerator.GetRequiredBufferSize("012345678901".AsSpan(), RmQREccLevel.M);
var modules = new byte[size.BufferSize];
RmQRCodeGenerator.CreateRmQRCode("012345678901".AsSpan(), RmQREccLevel.M, modules);
Span<char> destination = new char[RmQRCodeDecoder.GetMaxDecodedLength(size.Version)];
var ok = RmQRCodeDecoder.TryDecode(modules, size.Width, size.Height, destination, out var written, out _);

// Image scan, use RmQRCodeDecoder (QRCodeDecoder is Standard QR-only); rotation, mirroring,
// inverted colors, scaling and mild perspective are handled
using var bitmap = SKBitmap.Decode("rmqr.png");
var found = RmQRCodeDecoder.TryDecode(bitmap, out var scanned, out var scanInfo);
```

## License

MIT

## Acknowledgments

> - [aloisdeniel/Xam.Forms.QRCode](https://github.com/aloisdeniel/Xam.Forms.QRCode) : Qr Sample with Skia
> - [codebude/QRCoder](https://github.com/codebude/QRCoder) : QRCode generation algorithms

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