Sdcb.SimdCodecs

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Pure-managed image codecs for .NET 10: JPEG, PNG, TIFF, WebP, GIF, BMP, ICO / CUR, QOI, Netpbm, JPEG 2000 and JBIG2, plus EXIF and ICC, and HEIF / HEIC decoding as an opt-in package.

• No native dependencies. Runs wherever .NET does, including NativeAOT and browser-wasm, with identical output on every target.
• As fast as the native libraries. SIMD (AVX2, SSE, AdvSimd) with a scalar fallback: JPEG decode is 0.82× libjpeg-turbo's time, PNG decode 0.88× libpng's on photos, WebP decode 0.53–0.88× libwebp's (see Performance).
• Exact. WebP decode is byte-identical to libwebp, HEIF's HEVC planes to ffmpeg, PNG and lossless JPEG 2000 are bit-exact; the JPEG decoder is about 1 dB more accurate than libjpeg-turbo's default where chroma is upsampled.
• Low memory. Decode straight into your own buffer in any pixel layout; JPEG decode allocates 0 bytes of managed memory.

Every tile above was decoded by this library; the files are the LINQPad samples' images (how they were made).

Quick start

dotnet add package Sdcb.SimdCodecs

using Sdcb.SimdCodecs;
using Sdcb.SimdCodecs.Abstractions;
using Sdcb.SimdCodecs.Jpeg;

byte[] file = File.ReadAllBytes("photo.webp");   // JPEG, PNG, TIFF, WebP, GIF, BMP, ICO, CUR, QOI, Netpbm, JPEG 2000 or JBIG2

// The facade sniffs the format from the magic bytes. One call gives the pixels in the layout you ask for,
// turned upright by the EXIF orientation; it throws NotSupportedException for a format it does not decode
// and InvalidDataException with the codec's reason for a damaged file.
using PixelBuffer image = ImageCodecs.Decode(file, PixelFormat.Rgba32, new DecodeOptions { ApplyOrientation = true });

// Encode it as a JPEG: SIMD, baseline / optimised Huffman / progressive, 4:2:0 or 4:4:4.
// Passing image.Metadata keeps the ICC profile and Exif (its Orientation is already reset to 1).
using FileStream output = File.Create("photo.jpg");
ImageCodecs.Encode(image.Pixels, image.Width, image.Height, image.Format, ImageFormat.Jpeg, output,
    stride: image.Stride, options: new JpegEncodeOptions { Quality = 90 }, metadata: image.Metadata);

Common tasks:

// A server checks the header before it allocates anything.
if (!ImageCodecs.TryReadInfo(file, out ImageInfo info) || (long)info.Width * info.Height > 50_000_000)
    return Results.BadRequest();

// Decode into memory you own (a bitmap, a Mat, an upload buffer) in any layout, at any row stride.
// See the skiasharp and opencvsharp samples for an SKBitmap and a Mat.
ImageCodecs.TryDecodeInto(file, buffer, stride, PixelFormat.Bgra32Premultiplied);

// A thumbnail: JPEG scales by 1/2-1/8 in the DCT domain, every other format by a box filter.
using IDecodedImage small = ImageCodecs.Decode(file, new DecodeOptions { ScaleDenominator = 8 });

// HEIF / HEIC (iPhone photos): install Sdcb.SimdCodecs.Heif and register it once at start-up.
ImageCodecs.Register(HeifImageDecoder.Registration);

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