Discrepancy in Values

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Karin1610
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Discrepancy in Values

Post by Karin1610 » Sat Oct 28, 2017 12:57 pm

Another strange thing happening:

LSB 68 + RSB 69 + Width 823 = 960 -- Why does AW say 965?
Also, the 4 is positioned at Y=0, height is 1400, but the Bounding box value says 1403.
And 896–68=828, not 823 which is the actual width.
glitch.jpg
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Erwin Denissen
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Re: Discrepancy in Values

Post by Erwin Denissen » Sat Oct 28, 2017 4:21 pm

Width is the actual (visual) width of the outline, while LSB and RSB are based on the most left and most right points. In your case one or more are off curve points.

It is best to avoid off-curve extremes. You can use the font validation features to add on-curve extremes.
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Re: Discrepancy in Values

Post by Karin1610 » Sat Oct 28, 2017 7:20 pm

Ah. I just wonder where that comes from or how to avoid it. I create my glyphs in Corel Draw, then export them as eps files. In Corel Draw there isn't such a thing like off curve points. All points are always on the outline.
To be honest, I don't quite know what off-curve extremes or on-curve extremes are because I never adjusted anything on my glyphs within FC.

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Re: Discrepancy in Values

Post by Bhikkhu Pesala » Sat Oct 28, 2017 7:41 pm

Off-curve extremes can be detected and fixed using the Validation Toolbar. The blue node in the illustration is an off-curve extreme. Click the button to add on-curve extremes, which will fix the problem. Or run the Validation wizard to fix an entire font at once.
Off-curve Extremes.png
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Karin1610
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Re: Discrepancy in Values

Post by Karin1610 » Sat Oct 28, 2017 8:16 pm

Thanks for showing me this. I'll try fixing it tomorrow.
Bhikkhu Pesala wrote:
Sat Oct 28, 2017 7:41 pm
Or run the Validation wizard to fix an entire font at once.
I tried this Validation Wizard once after finishing all my glyphs, and it did say it discovered problems, so I had it fix them, but those glyphs were messed up. The outlines where changed visibly, so I undid it and since everything works fine in every program I tested the font, I just didn't worry about this anymore.

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Re: Discrepancy in Values

Post by Bhikkhu Pesala » Sat Oct 28, 2017 8:26 pm

Any change in the outlines should be negligible.

Off-curve extremes can cause clipping of they project beyond the WinAscent or WinDescent metrics.

See this earlier thread
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Re: Discrepancy in Values

Post by Karin1610 » Sun Oct 29, 2017 9:18 am

Bhikkhu Pesala wrote:
Sat Oct 28, 2017 8:26 pm
Any change in the outlines should be negligible.
The problem is, since this will be a school font mostly for first graders it will be used in large font sizes rather than small ones.
Just now I tried fixing the the detected off-curve problems automatically and then printed some text in a large font size. Some changes it made do show noticeably, more than I'm willing to tolerate.
So I tried fixing those points manually, but I just can't get those points to work the way I want.

I'd really like to understand why this off-curve problem even happens. Is it the way FC interprets the eps files that I produce in Corel Draw?
Right now I'm really a bit helpless as for how to solve this problem. :?:

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Re: Discrepancy in Values

Post by Bhikkhu Pesala » Sun Oct 29, 2017 10:12 am

Attach an EPS file and see if anyone can see what the issue is.

You will need to zip the EPS file first to attach it.
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Re: Discrepancy in Values

Post by Erwin Denissen » Sun Oct 29, 2017 11:09 am

Something more radical, but might be worth a try:

Design your font as an OpenType font with CFF based outlines, as those use cubic curves which are also what is used in most vector drawing software. So your eps image will then be (almost) 100% equal. However do be aware most vector editing software doesn't always show the off-cirve points, also know as control points, so it might reveal more than you were aware of (e.g. extreme off-curve points).

To import or paste eps without conversion to TrueType based outlines (quadratic bezier curves), you need to set the Outline Format to CFF (PostScript) in the TrueType/OpenType Font Export Settings.
cubic.png
cubic.png (8.88 KiB) Viewed 2207 times
You can then also copy and paste back into most vector editing software.

This might change part of your design workflow, which is not always desired. Let us know your results.
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Re: Discrepancy in Values

Post by Karin1610 » Sun Oct 29, 2017 12:15 pm

@ Bhikkhu Pesala - thank you, I've attached the "l" which shows off curve points in FC.

@ Erwin - so that means I would have to change this setting to CFF, then import all the glyphs anew?
Attachments
l.rar
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Re: Discrepancy in Values

Post by Bhikkhu Pesala » Sun Oct 29, 2017 12:47 pm

Your glyph has a lot more nodes than it needs. The top is fine, but the bottom curves only need the same number of points at the top curve.
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Re: Discrepancy in Values

Post by Alfred » Sun Oct 29, 2017 12:54 pm

Karin1610 wrote:
Sat Oct 28, 2017 7:20 pm
Ah. I just wonder where that comes from or how to avoid it. I create my glyphs in Corel Draw, then export them as eps files. In Corel Draw there isn't such a thing like off curve points. All points are always on the outline.
In most vector drawing applications, off-curve points are represented as control handles, linked by straight lines to the nodes (i.e. on-curve points) that they control. As Erwin has indicated, cubic rather than quadratic Bézier curves are usually used, so each node has two control handles (instead of having one control handle shared between the nodes on either side of it).
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Re: Discrepancy in Values

Post by Karin1610 » Mon Oct 30, 2017 2:41 pm

Bhikkhu Pesala wrote:
Sun Oct 29, 2017 12:47 pm
Your glyph has a lot more nodes than it needs. The top is fine, but the bottom curves only need the same number of points at the top curve.
The original "l" I used had fewer nodes. I tried all kinds of things to avoid getting off-curve extremes. Adding some nodes was one attempt and the result in FC was better than with the one I used first, so I left it.
Alfred wrote:
Sun Oct 29, 2017 12:54 pm
In most vector drawing applications, off-curve points are represented as control handles, linked by straight lines to the nodes (i.e. on-curve points) that they control. As Erwin has indicated, cubic rather than quadratic Bézier curves are usually used, so each node has two control handles (instead of having one control handle shared between the nodes on either side of it).
Now I finally understand the difference between cubic and quadratic Bézier curves, lol! Thanks for that!

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