Need help transforming image with minimal distortion

[rich2005]

(01-16-2025, 07:03 PM)PeytonR Wrote: I've tried most of the GIMP transform tools and haven't found one that does what I want.
Attached should be a "before" picture of a grid in which all squares are the same size and shape.
I want to bring the bottom 2 corners of the image inward to achieve a keystone effect. I expect the squares in each row to become quadrilaterals (4 sided polygons) which are narrower than the original squares.
----snip----

Bearing in mind the original question

Looking at Ofnuts plugin ofn-trapeze-transform.py I can not get an "easy" outcome and it is slow, rendering strips of the image.

   

Back to the gmic_gimp_qt plugin http://www.gmic.eu  and using one of the map filters - triangular projection. more explanation than the earlier animation.

   

(1) Transparency required. Use Layer -> Transparency -> Add Alpha Channel
(2) It is a Map projection and needs a North and South pole with center of the image the Equator. Double the height of the image. Gimp can do the arithmetic for you if you want height*2 or enter the value yourself.
(3) The default is image at the top. Click-Drag the image icon down to bottom in the small preview window.
(4) Check that Fill width is set to transparency and click resize.

---- on to gmic--- bottom of the filters menu

(5) There are 600+ filters. Use the search for map
(6) Locate the Triangular Projection filter.
(7) Set the Background Opacity to zero
(8) Adjust the Width to suit and OK to apply the filter

(9) To remove the excess transparency, Image -> Crop to Content. Easy.