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[ft-devel] [GSoC] [Doubt] Difference in Glyph Dimensions


From: k kushal
Subject: [ft-devel] [GSoC] [Doubt] Difference in Glyph Dimensions
Date: Tue, 18 Jul 2017 01:44:44 +0530

When rendering glyphs, I came across same glyph having different
dimensions (height / width) in different versions (I was comparing glyphs
rendered by version 2.6.3 and the latest git version)
Note: I needed images to be of the same height / width to form sprite sheets.

As a solution, Till now,
When I wanted to compare those, I added white lines (as padding)
on the edges (rows / columns )of the smaller image to compensate for the
difference and then did the comparison.

Issue.
For example, there are two glyphs A,A' and B,B'
Let's say Height ( A ) != Height ( A' ) and also Height ( B ) != Height ( B' )
Here A and A' will be aligned ( see mis-aligned.png attached to know what
I mean by aligned ) iff the white columns are added to the top of the image
with smaller height. And in the case of B and B' it is the opposite.
In some cases it is both top and bottom.
This totally depends on the glyph itself. I think there is no way to guess which
sides to fill and by how much to align them.

Turns out some glyphs have differences that are only changes in a particular
dimension. (For example: See false-negative.png , the first two sub-images
(rendered glyphs) are the stitched together after inserting white lines as told above.)
In this case, the glyphs are aligned after padding.
Here, it seems like there is *no* difference at all.

Is it a bad Idea to do this (adding rows / columns )?

What should I do for comparing these type of glyphs?
Should I *mark* these particular glyphs in the list-view web-page to
show that the dimensions are different ?

As this problem arises *only* when we want to highlight the pixels that are different,
( adding effects/visualizations )
we can skip doing that for these kind of glyphs and show the rendered glyphs
only and glyph metrics comparison table .

I've pushed code to generate the list-view web-page yesterday.
(With sorting of columns as asked). Is there anything to be added ?
I've attached a screen-shot of the list-view web-page.

Also, I will push the detailed comparison web-page code ASAP.

Attachment: false-negative.png
Description: PNG image

Attachment: mis-aligned.png
Description: PNG image

Attachment: list-view.png
Description: PNG image


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