Image Resizer

Custom Overlay plugin

New in V3.2

This is an example plugin. It is useful as a starting point, but is not subject to the same standards of maintenance and backwards-compatibility that normal plugins are. It does not have a NuGet package or precompiled binaries.

This plugin is for drawing image overlays using pre-determined x1,y1,x2,y2,x3,y3,x4,y4 coordinates that are relative to the base file's width and height. It supports any parallelogram, and can use any virtual path for loading the overlay image.

Implement the IOverlayProvider interface to provide your own querystring parsing and/or database code. Add a constructor that accepts a NameValueCollection as an argument, so it can be dynamically created by the plugin.

The plugin includes two implementations:

  1. QuerystringOverlayProvider - Understands &customoverlay.coords=x1,y2,x2,y2,x3,y3,x4,y4 &customoverlay.align=topright &customoverlay.image=alphanumeric.png Points must be in clockwise order, top-left is x1,y1.
  2. A CachedOverlayProvider implementation that is database-specific and uses the &designid=504&mastid=8540&colorid=9633 syntax.

See Samples\CustomOverlaySample for an example

Generic Installation

  1. Add a project reference to Samples/CustomOverlayPlugin. You may want to copy it to your directory.

  2. In the plugins section, add the following

    <add name="CustomOverlay" provider="MyNamespace.MyOverlayProviderClass, MyAssembly" arg1="value1" arg2="value2.." ignoreMissingFiles="false" />

Generic settings

  • ignoreMissingFiles (defaults to false). If set, a missing overlay will just result in the base image appearing without the overlay instead of an exception.
  • smoothing - The smoothing quality setting to use.
  • compositing - The compositing quality setting to use.

Installation using QuerystringOverlayProvider

  1. Add a project reference to Samples/CustomOverlayPlugin. You may want to copy it to your directory.

  2. In the plugins section, add the following

    <add name="CustomOverlay" provider="ImageResizer.Plugins.CustomOverlay.QuerystringOverlayProvider, ImageResizer.Plugins.CustomOverlay" overlayFolder="~/images/overlays/" ignoreMissingFiles="false" />

Installation using CachedOverlayProvider

  1. Add a project reference to Samples/CustomOverlayPlugin. You may want to copy it to your directory.

  2. In the plugins section, add the following

    <add name="CustomOverlay" provider="ImageResizer.Plugins.CustomOverlay.CachedOverlayProvider, ImageResizer.Plugins.CustomOverlay" connectionStringName="database" sqlDependencyName="dpdb" overlayBasePath="~/images/foldertooverlays" ignoreMissingFiles="false" />

  3. Ensure you have a connection string by the name of 'database' in Web.config.
  4. Ensure overlayBasePath points to the folder containing the overlay images.
  5. Configure SqlCacheDependency (or remove the sqlDependencyName attribute) - but you won't get invalidation when data changes - images won't update until the app pool restarts.

Configuring SqlCacheDependency

(Only required for CachedOverlayProvider)

A little bit of work is required to get ASP.NET and SQL talking about changes.

First, you'll need to run aspnet_regsql.exe on the database and on each of the tables involved ("LogoDesignMap", "LogoDesign", "LogoUsage", "Organization", "LogoImage2", "Color").

Second, you'll need to set up Web.config. Make sure you have a connection string already, then add the element as shown in the below example:

Pay particular attention that the 'name' value below ("dpdb") matches the sqlDependencyName value from above, and that the connectionStringName matches the connectionStringName from above.

<connectionStrings>
  <clear/>
  <add name="database" 
      connectionString="Data Source=REA_ANDREW-PC\SQLEXPRESSADV;Initial Catalog=Forum; 
      Integrated Security=true;" providerName="System.Data.SqlClient"/>
</connectionStrings>
<system.web>
  <caching>
      <sqlCacheDependency pollTime="1000" enabled="true">
      <databases>
        <add connectionStringName="database" name="dpdb"/>
      </databases>
      </sqlCacheDependency>
  </caching>
</system.web>

This plugin (Custom Overlay plugin) is part of the Essential edition

Where is the plugins section?

The <plugins> section is located in Web.config, and is nested inside the <resizer> element, which is nested inside <configuration>. For examples, see this sample Web.config file.

Where can I find the dll?

We prefer that you install via NuGet, but you can also find the plugin DLL files in the /dlls/release folder of your download.

How do I typically install a plugin via Web.Config?

  1. In Visual Studio, right click on your project and choose "Add reference". Browse to the plugin DLL and click "OK".
  2. In the <plugins> section of Web.config, insert <add name="PluginName" />
  3. Look at the plugin documentation to see what configuration options (if any) are available.

How do I typically install a plugin via code?