SAMPLE: Code to Extract an Icon from a Windows .EXE File

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

SUMMARY

WINRES is a file in the Microsoft Software Library that provides the necessary structures to extract an icon from a Windows .EXE file.

NOTE: In Windows version 3.1 there is a new function named ExtractIcon() in SHELL.DLL that performs this type of functionality. However, this article and sample still provide a useful example of extracting .EXE file information.

Download WINRES.EXE, a self-extracting file, from the Microsoft Software Library (MSL) on the following services:

• Microsoft Download Service (MSDL)

        Dial (206) 936-6735 to connect to MSDL
        Download WINRES.EXE (size: 30738 bytes) 
  

• Internet (anonymous FTP)

        ftp ftp.microsoft.com
        Change to the \SOFTLIB\MSLFILES directory
        Get WINRES.EXE (size: 30738 bytes) 
  

MORE INFORMATION

The following is a list of the files in the WINRES archive and how each is used:

   Filename     Description
   --------     -----------

   WINRES.C     Application to extract .ICO and .EXE resource
                information

   WINOPEN.C    Used to display FileOpen dialog box and retrieve the
                filename

   DUMPRES.H    .EXE header information derived from the "MS-DOS
                Encyclopedia" (Microsoft Press)

Program Theory of Operation

To retrieve the icons from an .ICO or .EXE file, the program must retrieve the device independent bitmaps (DIBs) that make up the icon. Although this is a difficult process, the necessary information is documented in the "MS- DOS Encyclopedia." A comment with each structure in the DUMPRES.H file provides a cross-reference to the relevant information in the "MS-DOS Encyclopedia." The .ICO file format is documented in Chapter 9, "File Formats," in version 3.0 of the "Microsoft Windows Software Development Kit Reference Volume 2."

Potential Enhancements to the Code

1. Choosing the Display Info menu item provides a listing of resource information about all resources in the file. This information should be placed into a list box, therefore the user will be able to scroll through the list. Currently, the information sometimes scrolls off the screen.

2. Pressing the I key on the keyboard will display the TEST.ICO file. Currently, this filename cannot be changed.

3. This version of the program does not support Windows 2.x .EXE files.

Differences Between .ICO Files and .EXE Resources

There are only three differences between an icon in an .ICO file and one in an .EXE file:

• Offset to the DIB

  In an .ICO file, the offset to the DIB is the last item in the icoResourceCount structure, icoDIBOffset. In an .EXE file, the offset is found in the offset for each individual icon, the rc_desc.wOffset field.

• The two reserved WORD fields before the icoDIBSize field in the .ICO file are filled in:

        icoPlanes   -- Filled from the BITMAPINFOHEADER.biPlanes
        icoBitCount -- Filled from the BITMAPINFOHEADER.biBitCount
  
     This allows an application to determine which icon is best suited
     for the display without having to read the DIB.
  
  

• The icoDIBOffset is changed from a DWORD in the .ICO file to a WORD in the .EXE file. The offset value in the .ICO file is changed to represent an ordinal number that ranges between 1 (one) and n (the total number of icons in the .EXE file). Note that one ICON group (value RT_GROUP_ICON), which is one icon rendered at two different resolutions, is counted as two separate icons (value RT_ICON).