All icon and other PNG files are derived from a Photoshop file.  The Photoshop
file has multiple layers, which need to be enabled or disabled when producing
the various PNG files.  A full description of which layers need to be adjusted
is in Photshop Notes.xlsm, an Excel worksheet.

Smaller icons require manual editing for best appearance.

For Windows-----------

Windows .ico file should contain 16x16, 32x32, 48x48, and 256x256 images.  We
also include 24x24 for Windows XP compatibility.
A .ico file can be built at the website icoconvert.com.

For macOS -----------	

macOS naming conventions for icons:
icon_64x64.png 		(for standard resolution)
icon_64x64@2x.png 	(for hi-res Retina icons)
				
The macOS hi-res icons are double the size of the standard icons.
ex. the icon_128x128@2x is actually a 256x256 image.  Mac automatically 
selects the correct one based on the type of display.
					
macOS defaults to using pt (point) instead of px (pixel) for image size. Set the image DPI to 72 px for the 
original image and it should not cause any sizing issues if using px. 

Mac has a native command line tool, "iconutil", for creating *.icns file.
Create the images, listed below, in a folder named oscar-icons.iconset (note the extension on a folder)
For more information check "man iconutil" or the Mac Developer documentation at:
https://developer.apple.com/library/archive/documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/Optimizing/Optimizing.html

macOS .icns file should contain:

    (Icon size in px)
    
    icon_16x16.png
    icon_16x16@2x.png	(32x32 image)
    icon_32x32.png
    icon_32x32@2x.png	(64x64 image)
    icon_128x128.png
    icon_128x128@2x.png	(256x256 image)
    icon_256x256.png
    icon_256x256@2x.png	(512x512 image)
    icon_512x512.png
    icon_512x512@2x.png	(1024x1024 image)
	

The macOS *.icns file can also be edited on Windows using the Greenfish Icon Editor.