Get icons for common file types

问题:

I want to get the icons of common file types in my dll. I am using vc++. I only have the file extension and mime type of the file based on which I want to get the icon for the file.

Can someone please tell me how I can do that? (The method available in vc++ needs the user to give the path of the file for which the icon is needed. I do not have access to any such file)

Thanks.

回答1:

Shell API

You can get them from the shell by calling SHGetFileInfo() along with the SHGFI_USEFILEATTRIBUTES flag - this flag allows the routine to work without requiring the filename passed in to actually exist, so if you have a file extension just make up a filename, append the extension, and pass it in.

By combining other flags, you'll be able to retrieve:

• A large or small icon as determined by the system configuration: SHGFI_ICON|SHGFI_LARGEICON or SHGFI_ICON|SHGFI_SMALLICON
• A large or small icon as determined by the shell configuration: SHGFI_ICON|SHGFI_LARGEICON|SHGFI_SHELLICONSIZE or SHGFI_ICON|SHGFI_SMALLICON|SHGFI_SHELLICONSIZE
• The index of the icon in the shell's image list along with the appropriate image list: SHGFI_SYSICONINDEX
• The path and filename of the actual module where the icon is stored (along with the icon index in that module): SHGFI_ICONLOCATION

Examples

// Load a System Large icon image
SHGetFileInfo( szFileName, FILE_ATTRIBUTE_NORMAL, &shfi, sizeof(SHFILEINFO), 
   SHGFI_USEFILEATTRIBUTES | SHGFI_ICON | SHGFI_LARGEICON);

// Load a System Small icon image
SHGetFileInfo( szFileName, FILE_ATTRIBUTE_NORMAL, &shfi, sizeof(SHFILEINFO), 
   SHGFI_USEFILEATTRIBUTES | SHGFI_ICON | SHGFI_SMALLICON);

// Load a Shell Large icon image
SHGetFileInfo( szFileName, FILE_ATTRIBUTE_NORMAL, &shfi, sizeof(SHFILEINFO), 
   SHGFI_USEFILEATTRIBUTES | SHGFI_ICON | SHGFI_SHELLICONSIZE);

// Load a Shell Small icon image
SHGetFileInfo( szFileName, FILE_ATTRIBUTE_NORMAL, &shfi, sizeof(SHFILEINFO), 
   SHGFI_USEFILEATTRIBUTES 
   | SHGFI_ICON | SHGFI_SHELLICONSIZE | SHGFI_SMALLICON);

If you want to draw such an icon, use something like this:

// Draw it at its native size
DrawIconEx( hDC, nLeft, nTop, hIcon, 0, 0, 0, NULL, DI_NORMAL );

// Draw it at the System Large size
DrawIconEx( hDC, nLeft, nTop, hIcon, 0, 0, 0, 
            NULL, DI_DEFAULTSIZE | DI_NORMAL );

// Draw it at some other size (40x40 in this example)
DrawIconEx( hDC, nLeft, nTop, hIcon, 40, 40, 0, NULL, DI_NORMAL );

The icon handle as well as the file system path can be obtained from the SHFILEINFO structure:

typedef struct _SHFILEINFOA
{
        HICON       hIcon;                      // out: icon
        int         iIcon;                      // out: icon index
        DWORD       dwAttributes;               // out: SFGAO_ flags
        CHAR        szDisplayName[MAX_PATH];    // out: display name (or path)
        CHAR        szTypeName[80];             // out: type name
} SHFILEINFOA;

Keep in mind that you must free the obtained icon by passing hIcon to DestroyIcon() after you're done with it.

回答2:

Identify the icon information from the registry, the associate file type and program that handles the file and extract the icon from the file. http://www.codeproject.com/KB/shell/iconextract.aspx