Extract icons from EXE or DLL files

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Introduction

The class I introduce in this article is for extracting an icon from an EXE or DLL file. Though it's common to use the ExtractIconEx() Win32 API function for this purpose, ExtractIconEx() can't extract all the variations of an icon.

I had faced the problem, and made a class 'IconExtractor' as the solution to the problem.

Using the code

To use this class, instantiate it first with the filename from which you want to extract the icons. You should dispose it after use.

Then, call the GetIcon() method with the index of the icon you want, to extract the specified icon. The index is same as the nIconIndex for ExtractIconEx(). This method returns a System.Drawing.Icon object containing all the variations in size and color depth. You can use it for Form.Icon, NotifyIcon.Icon, etc. The proper variation will be selected by the system.

Use the SplitIcon() static method if you want to split the variations into individual instances. This method returns an array of icons, each element containing one of the variations.

using TKageyu.Utils;

...

using (IconExtractor ie = new IconExtractor(@"D:\sample.exe")) 
{
    Icon icon0 = ie.GetIcon(0);
    Icon icon1 = ie.GetIcon(1);

    ...
    
    Icon[] splitIcons = IconExtractor.SplitIcon(icon0);

    ...
}

How it works

The icons and other materials are embedded in the executable file in binary form. Those pieces of binary data are called 'resources'. They can't be read directly with .NET classes, because they are different from the managed resources that the .NET Framework can handle. They should be read with Win32 API functions such as FindResource(), LoadResource() etc.

This class reads binary data by using the functions in the GetResourceData() private method. The parameters given to the method are collected when the class is instantiated. The binary data is in similar form to an .ico file, and can be converted easily to be equivalent to an .ico file. It is given to the icon constructor after conversion, and will be parsed as read from an .ico file. The conversion is done in the CreateIcon() method.