I stumbled into this issue through a series of improbable events. 
While trying to edit a map that was 5300 pixels x 2200 pixels (approx 11 MB file size), I was having real problems with "jaggies" when drawing straight lines using the pencil tool in conjunction with the [shift] key, anytime I was drawing a line outside of strict 0-90-180-270 degree coordinates. (reading elsewhere here I've already discovered that my main problem was that I was too stupid to realize that the pencil tool does not anti-alias, so I switched to the brush tool, and that problem is now solved).I may end up preferring the "stroke path" function....once I get more experience with it.
ANYWAY, before I came here and got a workable solution, I was trying to improvise a solution.
Initially, it seemed to make perfect sense to me to just use the transform/rotate image function, and rotate the entire image to the position needed to draw the line straight at 90/180/270 degrees with the pencil tool. And it worked, giving me nice, crisp lines at whatever angle I set up for.
But, I needed to draw 50+ lines, oriented at least a dozen different rotational positions. Waiting for an image of that size to rotate, got to be a chore in itself, especially given the number of times I needed to set up differently.
But it seemed to be working, until I got to my 5th distinct rotation, and I noticed that the (original) text on the map was starting to get blurry.
(note: using *.PNG image format)
Evidently there is some loss of information that accompanies each rotation? I've rotated images in the past and never really noticed degradation of the image before.
Are you folks who are familiar with the code aware of why this might be happening? Is there a setting available that can "sharpen the pencil" that the program uses to calculate the rotations? (such as the Image/precision list box selector) not sure if that is the intent, or not.
Just curious if this is the intent and function of the "precision" selector.
Doubtful that I'll ever try this again for the purpose of beating the anti-alias demons, but I do occasionally rotate images for legitimate purposes, so it would be nice to know if there is a fix available. Thank you in advance for your patience in addressing this unusual request.
Gimp 2.10
While trying to edit a map that was 5300 pixels x 2200 pixels (approx 11 MB file size), I was having real problems with "jaggies" when drawing straight lines using the pencil tool in conjunction with the [shift] key, anytime I was drawing a line outside of strict 0-90-180-270 degree coordinates. (reading elsewhere here I've already discovered that my main problem was that I was too stupid to realize that the pencil tool does not anti-alias, so I switched to the brush tool, and that problem is now solved).I may end up preferring the "stroke path" function....once I get more experience with it.
ANYWAY, before I came here and got a workable solution, I was trying to improvise a solution.
Initially, it seemed to make perfect sense to me to just use the transform/rotate image function, and rotate the entire image to the position needed to draw the line straight at 90/180/270 degrees with the pencil tool. And it worked, giving me nice, crisp lines at whatever angle I set up for.
But, I needed to draw 50+ lines, oriented at least a dozen different rotational positions. Waiting for an image of that size to rotate, got to be a chore in itself, especially given the number of times I needed to set up differently.
But it seemed to be working, until I got to my 5th distinct rotation, and I noticed that the (original) text on the map was starting to get blurry.
(note: using *.PNG image format)
Evidently there is some loss of information that accompanies each rotation? I've rotated images in the past and never really noticed degradation of the image before.
Are you folks who are familiar with the code aware of why this might be happening? Is there a setting available that can "sharpen the pencil" that the program uses to calculate the rotations? (such as the Image/precision list box selector) not sure if that is the intent, or not.
Just curious if this is the intent and function of the "precision" selector.
Doubtful that I'll ever try this again for the purpose of beating the anti-alias demons, but I do occasionally rotate images for legitimate purposes, so it would be nice to know if there is a fix available. Thank you in advance for your patience in addressing this unusual request.
Gimp 2.10