Transformation tools leave fuzzy white or transparent space at edges
GIMP version: 2.10.6
Operating System: Windows 10, 64 bit
Package: Installer from gimp.org
Description of the bug
Most if not all the transformation tools do not handle the edges of the transformed selection properly. The problem is less obvious with small files, but is unavoidable when working with typical camera output files.
Reproduction
Is the bug reproducible? Always
Reproduction steps:
- Open a jpg and enlarge its canvas on the right side with a white background (flatten the image).
- Using the Rectangle Select Tool (or the Free Select tool), select a long narrow vertical rectangle (without feathering) anywhere through original image, including at least some darker areas. Float it, or not.
- Choose the Unified Transform Tool (or any of the others that can stretch the selection in one axis).
- Using the central handle, stretch the selection horizontally, out into the added white area.
- While still in preview mode, note that the vertical edges look normal no matter how far the image is stretched.
- Hit the 'Transform' button to complete the transformation.
- If the stretch was small, the marching ants will probably be hiding a very narrow (typically one pixel) white line (presuming the background of the image is white) on both sides of the stretched area.
- If the stretch was more extreme, say 10 or 20 times the width of the original selection, symmetrical, feathered edges will be quite evident on both sides of the 'stretched' area.
- Undo the transformation and selection
- Using the Bucket Fill tool, fill the white area with a bright colour.
- Repeat the transformation experiment (Steps 2 - 8) and notice that these unwanted feathered edges appear to be transparent (actually just blended?).
Expected result: Clean, hard edges (as shown in the preview) for the stretched area
Actual result: Narrow white lines to broadly feathered edges on either side of the stretched area
Additional information
Most of the Transform dialog options were investigated for their effect on the problem, including Direction, Interpolation method, Clipping, Constrain, From pivot, and Pivot. None of these seemed to have any impact.
This bug was first noticed in 2.10; I have not re-installed 2.8 in order to be able to say categorically that it was not in that version, but I'm fairly certain that it was not.