Base64Codec

ImageGlass Base64 Sample Codec Plugin

A minimal, cross-platform native codec plugin for ImageGlass v10 that teaches the in-process native plugin ABI (ImageGlass.SDK.Plugins / IGNativeAbi) with the smallest interesting codec: it adds support for .b64 files.

Extension	What it does
.b64	Reads a base64-encoded image from a text file and decodes it to a raster image

A .b64 file is just a text file holding a base64 string. Two shapes are accepted:

1. A raw base64 payload — iVBORw0KGgoAAAANSUhEUgAA...
2. A data URI — data:image/png;base64,iVBORw0KGgo...

Whitespace and newlines anywhere in the payload are ignored.

What it demonstrates

• Exports the well-known C entry point ig_plugin_get_api
• Advertises one static-image codec (plugin.base64.codec) for .b64
• Implements LoadMetadata and DecodeStaticRaster:
  1. File.ReadAllText → strip an optional data:…;base64, prefix
  2. Convert.FromBase64String → original image bytes (PNG/JPEG/WebP/…)
  3. SKCodec decodes those bytes straight into a native 32bpp premultiplied BGRA buffer (IGPixelFormat.Bgra8Unorm)
• Allocates pixel buffers with NativeMemory.Alloc and releases them in a thread-safe FreePixelBuffer
• Honors the host-supplied opaque cancellation token at coarse boundaries
• Leaves the animation entry points null (static images only)

Unlike a format-specific codec, the heavy lifting is delegated to SkiaSharp (the SDK's only dependency), so the plugin stays tiny and works on any platform SkiaSharp supports.

Build (Native AOT shared library)

dotnet publish samples/Base64Codec/Base64Codec.csproj `
    -c Release -r win-x64 -p:Platform=x64 `
    -o samples/Base64Codec/bin/publish/win-x64

This produces Base64Codec.dll next to igplugin.json. (Use -r linux-x64 / -r osx-arm64 and the matching -p:Platform for other targets.)

Install

Copy the published folder (containing the DLL, igplugin.json, and the native libSkiaSharp asset emitted by the AOT publish) into the host's plugins dir:

%LOCALAPPDATA%\ImageGlass_10\_plugins\Base64Codec\
    Base64Codec.dll
    igplugin.json
    libSkiaSharp.dll

On next launch the host discovers the manifest, loads the DLL, calls ig_plugin_get_api, and registers plugin.base64.codec for .b64.

Try it

Create a test file from any image:

[Convert]::ToBase64String([IO.File]::ReadAllBytes("photo.png")) `
    | Set-Content -NoNewline test.b64

Open test.b64 in ImageGlass — it renders as the original image.

Manifest schema

igplugin.json is deserialized into ImageGlass.SDK.Plugins.PluginManifest. Required fields: id, name, executable. The kind field defaults to "Codec" if omitted.

Notes

• Codec selection is priority-based. No built-in codec claims .b64, but the plugin still advertises metadataPriority/decodePriority of 200 so it reliably wins selection for that extension.
• Convert.FromBase64String ignores embedded whitespace, so wrapped/multi-line base64 files work without pre-processing.
• The codec reports IGColorSpace.Srgb; it does not extract embedded ICC profiles (SupportsColorProfiles = 0).