[Gimp-developer] some geometry stuff

[Nik Omul <nik-omul yandex ru>]

Hi!
A few thoughts here up for discussion
1. (see Attachment A) Is it possible to add Distance and Angle mesurements 
to the Paths Tool's /Polygonal mode/? 
Information could be displayed in the Status Bar just like for the Measure
tool. 
No need for Info window, though. 
Distance is relative  to the previous anchor, angle relative to x-axis or
user defined 
linear segment of another path. Specifying a segment sounds a bit too
complicated, 
so the users would probably have to create two-anchor linear path as a
reference axis.
Paths Tool (or Measure tool) recognizing varying axes would add 
extra power to GIMP graphics. 
It would probably create a mess with the keys assignment 
but maybe there is a solution for that too? 

2. Would be nice to have an option for the Measure Tool to constrain 
orientation line to integers other than 15 degrees. Say, in the tool options
menu 
checkbox for 1 and 3 in addition to default 15 gedrees. 
Am I the only one struggling with decimals?
Rotate tool has checkbox for 15 degree constraint, by the way.

3 (see Attachment B) Three additional marks on each Ruler corresponding to 
canvas' exact geometric center and to 'rule of third' imaginary lines. 
Could be implemented in Cfig filter preview window as well. 
The ability to snap guides to those marks would also be a must. 
Could be displayed as notches different  in color and shape from 
standard marks to avoid a confusion. Could be opted as Show/Hide in  
View/Rulers/hide-show midpoint, thirds. 
Allows to immediately find geometric center of a canvas,
rule of third points of intersection by navigating with a cursor 
across canvas. Snapping guides to these marks takes less time than:
a. Image/Guides/New Guide (by Percent) - Horizontal, 50% (33.3 then 66.6)  
b. Image/Guides/New Guide (by Percent) - Vertical, 50%, etc., 
not to mention calculations. I am aware of 3rd party plugin GAT, 
but many others may not.

4. This idea was actually proposed by a friend of mine who is 
a professional designer and no stranger to GIMP -  
a centroid (center of gravity) for irregular shaped selection 
as a reference point when using transformation tools. 
Problem with current procedure: rotation/pivot/lever point of Transform
tools 
for some irregular shapes (e.g. L-shaped or boomerang-like selection) 
is located outside object/selection, therefore, not a centroid. 
Dragging rotation point over the object without reference point 
gives inaccurate results. It matters  when repetitive trnsformations 
with the same object is required (e.g. a sequence of objects with 
different angles of rotation around exact centroid).
It's pure math, but I don't know if GIMP has the ability to calculate
centroids too.

Some of the ideas might have surfaced here before, 
I can't say I delved too deep to find that out. 
If need be, more thorough arguments for usability importance can be
provided.     
   
Perhaps, some ideas are too much for raster based editor. Need your
opinions.
Thanks for reading this!

http://i1271.photobucket.com/albums/jj621/NikOmul/edb82972.png Attachment A 
http://i1271.photobucket.com/albums/jj621/NikOmul/03de7f7c.png Attacment B 



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Nik O.
Никита Омуль
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