Re: [ft-devel] Splitting up the GSoC project (Re: Freetype-devel Digest, Vol 148, Issue 36)

[Hin-Tak Leung]

Mentioning html and javascript rings some alarms; and so does "mock-up images".

I think you may be thinking that there would be interesting differences for 
say, just glyphs A to Z for font X between freetype version P and Q. That's 26 
x 2 images, and quite eye-ball-able. put it 26 difference-images on a web page 
is easy.

The thing is, most of the 26 pairs are probably going to be identical; with a 
few showing small differences (1-pixel edges), and very few with large 
differences. One will not learn much about rendering differences from such a 
small sample.

Let's think of the ultimate goal: suppose there will be a freetype 2.9, say. 
You want to know if there is any important rendering changes against 2.8. So 
you throw all ~2000 fonts on a linux system, each with about ~1000 glyphs, at 
both, rendering for the 3 modes B/W, 8-bit gray, and LCD horizontal layout, at 
two pixel sizes, 15 and 30 (where hinting matters more in one and less in the 
other).

2000 x 1000 x 3 x 2 = 12,000,000 , or 12 million pair of images.

A substantial part of that 12 million pairs will be identical; a big part of 
the rest will be small number of pixels ar corners, etc; then out of the rest, 
most will be 1-pixel edges; and ideally, you only want to actually eye-ball the 
remaining. You do not want to eye-ball a handful of pixels differences at the 
sharp corners, etc.

I'd suggest:

1. Think of some ways of comparing images which does not involve your eye 
balls. You do not want to eye-ball even 1% of 12 million.

2. pick any one font, actually generate 26 images of A to Z, for two versions 
of freetype, to get a feeling of what sort of bitmap differences you are likely 
to get.