Bitmap Array in a single file

I am making an application for Solidwoks and downloaded some examples, some BMP images are used in it as the following view:

TheseimagesareusedasimagesinmenusasfollowsinC#code:

BitmapHandleriBmp=newBitmapHandler();cmdGroup=iCmdMgr.CreateCommandGroup2(mainCmdGroupID,TitleDr,ToolTipDr,"", -1, ignorePrevious, ref cmdGroupErr);
cmdGroup.LargeIconList = iBmp.CreateFileFromResourceBitmap("EngToolsSW.ToolbarLarge.bmp", thisAssembly);
cmdGroup.SmallIconList = iBmp.CreateFileFromResourceBitmap("EngToolsSW.ToolbarSmall.bmp", thisAssembly);
cmdGroup.LargeMainIcon = iBmp.CreateFileFromResourceBitmap("EngToolsSW.MainIconLarge.bmp", thisAssembly);
cmdGroup.SmallMainIcon = iBmp.CreateFileFromResourceBitmap("EngToolsSW.MainIconSmall.bmp", thisAssembly);

That is, it fetches the images separately within the same bitmap as if it were an Image Array. In the Solidworks documentation speak this way:

  

The bitmap or PNG file should contain all of the images for all of the large buttons and separators for this CommandGroup, in a single bitmap for both parent and child toolbars. Each image of each button must be 24x24. The images should use a 256-color palette. Use gray (RGB 192, 192, 192) for transparent areas in your graphic.

     

You can only set this property for the top-level CommandGroup.

available in this .

How can I create a bitmap of these?