Plugins

Add new image formats to MysticThumbs

Example plugin source on our GitHub repository to use as a template.

Other known open source plugins

Bob Voith's open source MysticThumbs plugins, including custom SVG, Video and DLL plugins.

Legacy plugin project for older pre-2026 MysticThumbs builds

Prior to MysticThumbs version 2026 the plugin system was much more limited. If you need to build or maintain a plugin for those older versions you can use the old plugin example source.

Download Download legacy pre-2026 example plugin source


Older existing plugin binaries should still work with newer MysticThumbs 2026+ versions, however due to the extensive re-engineering made, mileage may vary.

How to use

A Visual Studio 2022 project is supplied for convenience to get you up and running. This could be adapted to older or newer versions if required as it is very rudimentary.
Use this example project as a template to make your own.

Make one plugin project for each file type.
If you require different file types create new plugins for each.
You register each file format extension necessary for the file format, so you can for example register multiple extensions such as JPEG has with .jpg, .jpeg etc. you could register extensions .mtp, .mtp1, .mtp2 etc.

The core interface that must be implemented is the IMysticThumbsPlugin interface. In this example the class CExamplePlugin implements this.

MysticThumbs can request any number of these objects so it is very important that you do not use any static variables that could cause conflicts amongst concurrent running objects. Encapsulate everything in your class.

The documentation and comments in the MysticThumbsPlugin.h header file specify all the required information that you will need to successfully implement your own plugin.

For the purposes of the example, we use the .mtp extension (which is actually the extension used for MysticThumbs plugin DLLs) and generate a test pattern image dynamically of the requested thumbnail size.

IMysticThumbsPlugin::Ping and IMysticThumbsPlugin::Generate methods

This is the meat of the plugin.

In a typical plugin you will read from the passed IStream interface pointer that points to the head of the file being thumbnailed.
The Ping method parses the file and returns information about the dimensions of the image.
The Generate method reads the file and generates the thumbnail and returns the image data un-scaled.
It is not usually necessary to scale your image, and you can simply read and pass the full image back, this will yield the fastest and best results. MysticThumbs and Explorer will take care of scaling appropriate to control panel and operating system requirements. The MysticThumbsPluginGenerateParams parameter contains hints and parameters useful for generating your image.

If however, you are generating a thumbnail of an abstract nature, say for example a sound saveform, then your image could be of any arbitary size, and the MysticThumbsPluginGenerateParams params can be used to determine the best size to render to.

The params desiredWidth and desiredHeight parameters represent the size of the thumbnail that Explorer or QuickView is requesting at the time, this could be for example 32, 48, 96, 256 or even very large if requesting for preview purposes.
The params flags parameter gives you hints as to what the control panel settings are for your file extension, such as transparency, embedded thumbnail and scaling settings. This may be expanded upon in future releases.

Building

Ensure you build for both x86 and x64 platforms. This ensures compatibility with 32 bit apps on 64 bit Windows.
The example project already has the required project set up.

The x86 plugin should end with 32.mtp and the x64 plugin should end with 64.mtp, for example ExamplePlugin32.mtp and ExamplePlugin64.mtp.

Place both these files in the appropriate Plugins folder.
Shortcut buttons are available in the control panel plugins dialog that will open the folder for either the current user only (if using a shared machine and you want to either test or use a plugin only for yourself), or for all users, which will be the Plugins folder in the install folder.
Installing plugins for all users in the install folder will likely require administrator priveleges.

Register the plugin in the MysticThumbs control panel.

Using

Use the Plugins button, which opens the Plugins dialog where you can register and unregister plugins after installing them into the appropriate folder.
If the plugin loads successfully you will find it in the MysticThumbs control panel File Format drop list under an entry corresponding to the name you return in the method IMysticThumbsPlugin::GetName().
You can now use it just as you would any other natively supported file format with all the benefits of the control panel options.

To test this example plugin:

You now have all the MysticThumbs thumbnail options available for your file format!