BLF: Slant Angle Correction #112483

Harley Acheson · 2023-09-17T18:57:52+02:00

Harley Acheson commented

2023-09-17 18:57:52 +02:00

Internal change to slant direction of artificial italics (obliquing)
to match the counter-clockwise degrees of variable font SLNT values.

This is an internal correction only, without any user-facing change.

When rendering a glyph with a slant, we can do so in two ways. One is to change the value of the SNLT axis if the font is a variable type (Adobe MM, Apple's TrueType GX, OpenType variation fonts), or to to do an obliquing transform on the glyph if the font is not a variable type.

When adding the obliquing transform I had assumed that a positive value should move the top of the glyph rightward. Unfortunately, the OTF spec has a different idea for the SLNT variable axis, which treats these as counter-clockwise degrees. So a typical right-leaning design has a negative slant value. This was done so that this value can match an older "italicAngle" value in the "post" (PostScript) table.

This PR just aligns the obliquing transform direction with the SLNT axis direction. While there it decreases the range of change for obliquing to be within more sane values, and therefore also changes the value for the default "italic" setting.

Internal change to slant direction of artificial italics (obliquing) to match the counter-clockwise degrees of variable font SLNT values. --- This is an internal correction only, without any user-facing change. When rendering a glyph with a slant, we can do so in two ways. One is to change the value of the SNLT axis if the font is a variable type (Adobe MM, Apple's TrueType GX, OpenType variation fonts), or to to do an obliquing transform on the glyph if the font is not a variable type. When adding the obliquing transform I had assumed that a positive value should move the top of the glyph rightward. Unfortunately, the OTF spec has a different idea for the SLNT variable axis, which treats these as **counter-clockwise** degrees. So a typical right-leaning design has a negative slant value. This was done so that this value can match an older "italicAngle" value in the "post" (PostScript) table. This PR just aligns the obliquing transform direction with the SLNT axis direction. While there it decreases the range of change for obliquing to be within more sane values, and therefore also changes the value for the default "italic" setting.

Harley Acheson added 1 commit 2023-09-17 18:58:06 +02:00

cc3a893b45 BLF: Slant Angle Correction

Internal change to slant direction of artificial italics (obliquing)
to match the counter-clockwise degrees of variable font SLNT values.

Harley Acheson added this to the User Interface project 2023-09-17 18:58:24 +02:00

Harley Acheson merged commit 87fbe14cb4 into main

2023-09-17 18:58:45 +02:00

Harley Acheson referenced this issue from a commit

2023-09-17 18:58:46 +02:00

BLF: Slant Angle Correction

Harley Acheson deleted branch SlantAngle

2023-09-17 18:58:51 +02:00

Sign in to join this conversation.

No reviewers

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

BLF: Slant Angle Correction #112483