Colorful Transparency Algorithm (Windows)

thehorseisbrown

Dear font technology enthusiasts,

I let Windows draw a few glyphs with transparent background

 SetBkMode(glyph_hdc, TRANSPARENT);

 and to my astonishment, I saw this:



I think it's absolutely gorgeous and it looks intentional to me since the warm values are always on the right.

1) If it indeed is intentional, is the purpose to improve readability? What specifically does the coloring do to the eye?
Can someone elaborate or give some links?

2) I was about to store glyph bitmaps in a single channel and then color the glyphs inside a shader. This discovery makes me wonder how I could use these RGB values inside a shader to produce different colors.

Thank you

Thomas Phinney

This is a side effect of ClearType sub-pixel anti-aliasing, enlarged. I guess you must be using an older Windows API, since the newer stuff introduced in Windows 8 and onwards does not do this color fringing. (It also does not work as well, but that is the tradeoff.)

This book is a free download, and the early section has a nice, non-technical explanation of how the early versions of ClearType worked: https://docs.microsoft.com/en-us/typography/cleartype/clear-type-font-collection

Or this explanation from Wikipedia: https://en.wikipedia.org/wiki/ClearType