[ttml2] Incorrect illustration of example for tts:position (#1269)

ed-gh has just created a new issue for https://github.com/w3c/ttml2:

== Incorrect illustration of example for tts:position ==
In the published recommendation, section 10.2.34 [1], the example illustration [2] does not correctly illustrate the prose and alignment depicted above the example. The associated region's visible bottom edge has a distance of 48px from/to the bottom edge of the postioning rectangle having a vertical extent of 480px. However, the prose specifies "A percentage value component for a horizontal position offset is relative to the width of the positioning rectangle minus the width of the associated region. A percentage value component for a vertical position offset is relative to the height of the positioning rectangle minus the height of the associated region.", therefore the distance between the positioning rectangle's and associated region's reference edge(s) should be (480 - 92) * 0.1 = 38.8px, for which the coverage of the pixels in the bottom pixel row was/is already set correctly (as was/is the top pixel row).

[1] https://www.w3.org/TR/ttml2/#style-attribute-position
[2] https://www.w3.org/TR/ttml2/images/position.png

Presumably correct version:
![ttml-position-9px-down](https://github.com/w3c/ttml2/assets/28450948/9b877a79-be60-41a0-8c6d-098268063ee9)


Please view or discuss this issue at https://github.com/w3c/ttml2/issues/1269 using your GitHub account


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Received on Sunday, 21 January 2024 15:46:46 UTC