ThumbHash

This library is a .NET implementation of ThumbHash.

What is a thumbhash?

A very compact representation of a placeholder for an image. Store it inline with your data and show it while the real image is loading for a smoother loading experience.

|Image|ThumbHash|ThumbHash Image| |-----|---------|---------------| ||93 4A 06 2D 06 92 56 C3 74 05 58 67 DA 8A B6 67 94 90 51 07 19|<img alt="Flower ThumbHash" src="https://github.com/jzebedee/ThumbHash/blob/master/assets/flower_thumbhash_rust.png?raw=1" width=75 height=100>| ||A1 19 8A 1C 02 38 3A 25 D7 27 F6 8B 97 1F F7 F9 71 7F 80 37 67 58 98 79 06|<img alt="Tux ThumbHash" src="https://github.com/jzebedee/ThumbHash/blob/master/assets/tux_thumbhash_rust.png?raw=1" width=84 height=100>|

See a demo of ThumbHash for .NET in Blazor here

Learn more about ThumbHashes here.

Usage

The ThumbHash library has no external dependencies and can be used on its own, or with your choice of image library (e.g., SkiaSharp, ImageSharp) for rendering.

Images must be in the format of unpremultiplied RGBA8888 before working with ThumbHash.

Convert an image into a thumbhash (SkiaSharp)

using SkiaSharp;
using ThumbHashes;

using var original = SKBitmap.Decode("original.png");
using var rgba8888 = original.Copy(SKColorType.Rgba8888);
var thumbhash = ThumbHash.FromImage(rgba8888.Width, rgba8888.Height, rgba8888.GetPixelSpan());

Load a thumbhash and render it to RGBA

using ThumbHashes;

byte[] hash = Convert.FromHexString("934A062D069256C374055867DA8AB6679490510719");
var thumbhash = new ThumbHash(hash);

var (width, height, rgba) = thumbhash.ToImage();

Save a rendered RGBA to a PNG (SkiaSharp)

using SkiaSharp;

var (width, height, rgba) = thumbhash.ToImage();
var image_info = new SKImageInfo(width, height, SKColorType.Rgba8888, SKAlphaType.Unpremul);
using var sk_img = SKImage.FromPixelCopy(image_info, rgba);
using var sk_png_data = sk_img.Encode(SKEncodedImageFormat.Png, 100);

using var fs_png = System.IO.File.Create("test.png");
sk_png_data.SaveTo(fs_png);

Save a ThumbHash to a PNG data url (no dependencies)

string dataUrl = thumbhash.ToDataUrl();

<img src="@dataUrl" />

Support

Discussion and technical support is available on Discord.