[Gimp-developer] Cage transform and Warp transform

[Elle Stone <ellestone ninedegreesbelow com>]

Hi All,

I wanted to somewhat reshape some curved lines in a drawing, and tried 
the Cage transform, which I remember using a long time ago. After 
selecting the points, it took a long time for the cage transform to 
calculate the cage. But when trying to move a point on the cage, nothing 
happened. During all of this calculating plus "nothing happened", these 
lines were printed over and over to the terminal:

(gimp-2.9:30657): GEGL-CRITICAL **: gegl_buffer_get: assertion 
'GEGL_IS_BUFFER (buffer)' failed

Is there a bug? Or maybe I did something wrong? I reread through the 
on-line documentation 
(https://docs.gimp.org/2.9/en/gimp-tool-cage.html), but maybe I 
misunderstood what it says.


So I switched to the Warp transform, which worked very smoothly, 
quickly, responsively. It's like using a paint brush to warp the lines. 
The only catch was that after moving all the lines to where you want 
them, then you have to hit Return to actually apply the transform, which 
makes sense, but it took me a couple tries to figure this out.

Whoever programmed the warp transform, thank you!! This is such a nice 
way to gently reshape curved lines!

Jehan, is there any possibility that this warp transform could be made 
to work symmetrically, perhaps via the symmetric painting dialog? Or 
maybe it already does, but somehow I did something wrong?

Anyway, I made the transformed lines symmetric by duplicating the warped 
layer, flipping it around the horizontal axis, and applying a mask to 
hide the untranformed half of the image, which worked out just fine.

Best,
Elle