-------------------------------------------- On Mon, 29/5/17, Arvinder Bhathal <[email protected]> wrote: > > 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. > Although I'm unsure of the feasibility of it, my initial thought was to sum the pixel intensity differences between the baseline and test glyphs. Supposedly, these values could be stored for every glyph (although maybe not for 12 million) in an index, and we could consider these values when displaying the glyphs in the browser. This could help focus on the pairs with the greatest differences. However, as you've said in your second suggestion, a demo test will help determine what sort of comparison method will do.
I suspect for most glyphs in most fonts, you would get identical bitmaps for B/W and 8-bit rendering between not-too-distant freetype versions. (LCD is a different matter lately). So the actual numbers of glyphs you need to examine at all, is a small fraction of of a large number. Hence you might need to test quite a few fonts before you get "interesting" differences. As for quantifying differences - just summing pixel difference isn't a good measure. The differences is likely to be corner pixels or whole edges; i.e. a corner or a whole edge has moved slightly. I'd probably suggest somehow taking connected-ness into account - e.g. if you draw a square of 4x4 pixels, the 4 corner pixels being slightly darker/lighter, is less important than a whole edge of 4 pixels being darker/lighter. So you weight the difference by how many nearby pixels also show differences. A complicated shape will have a lot of sharp corners and the many corners may go darker/lighter, but these are less important than one stem of a simple shape going thicker. If you only count number of pixels differing, the first case might have a higher "score" of differences. Anyway, I think it is best your people have a go at looking at say, differences of bitmaps of say A-Z of one font you choose, and see what sort of difference you can get, to get a first-hand feeling about it. _______________________________________________ Freetype-devel mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/freetype-devel
