Sdcb.LibRaw

Sdcb.LibRaw is an advanced raw image processing library in C#, based on LibRaw.

NuGet Packages

Package	NuGet	License	Comments
Sdcb.LibRaw		MIT	Primary package
Sdcb.LibRaw.runtime.win64		LGPL-2.1-only OR CDDL-1.0	Windows x64 runtime
Sdcb.LibRaw.runtime.win32		LGPL-2.1-only OR CDDL-1.0	Windows x86 runtime
Sdcb.LibRaw.runtime.linux64		LGPL-2.1-only OR CDDL-1.0	Ubuntu 22.04 x64 runtime

Install

Please note all examples below need to install at least two of the following NuGet packages:

• Sdcb.LibRaw
• Sdcb.LibRaw.runtime.win64 (or other system-specific runtime packages)

All native packages are pre-compiled using vcpkg.

Please note the Sdcb.LibRaw.runtime.linux-64 package is only supported on Ubuntu 22.04. If you are using .NET in Docker, append jammy to your docker file. For example, write:

FROM mcr.microsoft.com/dotnet/sdk:6.0-jammy

Instead of:

FROM mcr.microsoft.com/dotnet/sdk:6.0

High-Level API Usage

The RawContext class wraps all LibRaw native functions for high-level API usage. See the following examples for more details.

Convert a RAW file into a Bitmap

using Sdcb.LibRaw;

using RawContext r = RawContext.OpenFile(@"C:\a7r3\DSC02653.ARW");
r.Unpack();
r.DcrawProcess();
using ProcessedImage image = r.MakeDcrawMemoryImage();
using Bitmap bmp = ProcessedImageToBitmap(image);

Bitmap ProcessedImageToBitmap(ProcessedImage rgbImage)
{
    rgbImage.SwapRGB();
    using Bitmap bmp = new Bitmap(rgbImage.Width, rgbImage.Height, rgbImage.Width * 3, System.Drawing.Imaging.PixelFormat.Format24bppRgb, rgbImage.DataPointer);
    return new Bitmap(bmp);
}

This code shows how to convert a RAW file into a Bitmap image. It's worth noting that the pixel format output by LibRaw is slightly different from Bitmap's. In the code above, rgbImage.SwapRGB(); is used to swap the red and blue color channels, i.e., converting RGB24 to BGR24.

Although the example is based on the .ARW photo, it actually supports almost all RAW format photos, including .CR2 and .DNG. You can retrieve a list of supported cameras using RawContext.SupportedCameras. As of the current version, it supports 1182 camera models:

Console.WriteLine("Sdcb.LibRaw supported cameras:");
foreach (string model in RawContext.SupportedCameras)
{
	Console.WriteLine(model);
}

Convert a RAW file into a Bitmap with custom settings

using Sdcb.LibRaw;

using RawContext r = RawContext.OpenFile(@"C:\a7r3\DSC02653.ARW");
r.DcrawProcess(c =>
{
    c.HalfSize = false; // Reduce the image size to 1/4
    c.UseCameraWb = true; // Use camera white balance; if false, the white balance will be controlled by UserMultipliers
    c.Gamma[0] = 0.35; // Adjust the exponent of the gamma curve
    c.Gamma[1] = 3.5;  // Adjust the slope of the gamma curve
    c.Brightness = 2.2f; // Brightness
    c.Interpolation = true; // Perform demosaic operation
    c.OutputBps = 8; // Output bit depth is 8 bits
    c.OutputTiff = false; // Output a TIFF file? If false, a Bitmap will be output
    // c.Cropbox = new Rectangle(4000, 2000, 1500, 700); // Crop the image
    // Many other settings can be explored at will
});
using ProcessedImage rgbImage = r.MakeDcrawMemoryImage();
using Bitmap bmp = ProcessedImageToBitmap(rgbImage);

Get a thumbnail from a RAW file

using Sdcb.LibRaw;

using RawContext r = RawContext.OpenFile(@"C:\a7r3\DSC02653.ARW");
using ProcessedImage image = r.ExportThumbnail(thumbnailIndex: 0);
using Bitmap bmp = (Bitmap)Bitmap.FromStream(new MemoryStream(image.AsSpan<byte>().ToArray()));

Modern RAW format photos often contain one or more JPEG format thumbnails. You can use Sdcb.LibRaw to extract these thumbnails. The above example shows how to extract the first thumbnail from an ARW photo and convert it into a Bitmap.

Save a RAW file as a local TIFF file

using Sdcb.LibRaw;

using RawContext r = RawContext.OpenFile(@"C:\a7r3\DSC02653.ARW");
r.SaveRawImage(@"C:\test\test.tiff");

Get metadata from a photo

using RawContext r = RawContext.OpenFile(@"C:\a7r3\DSC02653.ARW");
LibRawImageParams imageParams = r.ImageParams;
LibRawImageOtherParams otherParams = r.ImageOtherParams;
LibRawLensInfo lensInfo = r.LensInfo;

Console.WriteLine($"Camera: {imageParams.Model}");
Console.WriteLine($"Version: {imageParams.Software}");
Console.WriteLine($"ISO: {otherParams.IsoSpeed}");
Console.WriteLine($"Shutter Speed: 1/{1 / otherParams.Shutter:F0}s");
Console.WriteLine($"Focal Length: {otherParams.FocalLength}mm");
Console.WriteLine($"Artist Tag: {otherParams.Artist}");
Console.WriteLine($"Shot Date: {new DateTime(1970, 1, 1, 8, 0, 0).AddSeconds(otherParams.Timestamp)}");
Console.WriteLine($"Lens Name: {lensInfo.Lens}");

Performance and Comparison

Method	Time (ms)	Notes
Sdcb.LibRaw	1627
Windows Imaging Component	2177	Limited post-process
Magick.NET	5496	Limited post-process
Native C code	1619

As you can see, Sdcb.LibRaw has top-tier performance and its powerful image post-processing capability is based on Bayer data.

Low level API

API mapping reference

You can refer to following 2 pages to find out which C API is mapped to which C# API:

• Table styled mapping reference
• List styled mapping reference

Low level API usage

You can refer to existing unit tests for low level api usage.

License

The primary project(Sdcb.LibRaw) is licensed under the MIT license, but native packages are licensed under LGPL-2.1-only OR CDDL-1.0.

Please refer to LibRaw license for more details.

Conclusion

I understand that not many people need to process RAW format photos with code. However, with the development of smartphones, many mobile phones can now shoot RAW format photos. I firmly believe that this tool will bring great help to those who need it. I will continue to put effort into this field, add more features to Sdcb.LibRaw, and solve possible problems.

The above content is just a part of the features of the Sdcb.LibRaw library I created. Its powerful functions and high efficiency will bring unprecedented convenience to your processing of RAW format photos. I sincerely hope that more .NET enthusiasts can join me to explore the world of RAW photo processing. Sdcb.LibRaw will always remain useful and free. Let's look forward to more wonderful features!

If you are interested in trying Sdcb.LibRaw, welcome to visit my Github, and please give a Star 🌟