GNOME Bugzilla – Bug 338888
enhancement request for perspective transform tool
Last modified: 2018-05-24 11:49:05 UTC
Dear developers of GIMP, I have an idea about new facilities, which can be added to the GIMP in to the "perspective" tool: Between clasic tools is also the perspective. But sometimes designer need to have tool which behaves 'alike' the perspective but is more linear. Although it seems to be unlogical, the example picture could be better in explaining. In attached picture are three headlines, the one on the bottom is original, the one above it is the result of perspective and finally the one on the top is what I have meant and the perspective tool could do (with image, paths...). This transformation can be imagined as filling of tetragon without applying the linear perspective, and could give better results in some cases. The example picture, I have added, was made using the "Curve Bend", but this one do not support paths :-( But if perspective tool have abilty to make something like this, it will be great. Thank you for your time your user Jozef Sivek
Created attachment 63796 [details] explaining picture tu the bug#338888
It doesn't make much sense to drop such enhancement request into our bug-tracker without even given a pointer on how this feature could be implemented.
It is not that hard to understand, basically it is scaling with different scaling factors for each pixel-column, it probably also can be done with a transformation matrix.
If I understand correctly, what is being asked is to have the ability to apply a "curve bend" filter to a selection or path (as opposed to the drawable itself). If this were to be implemented, I do not think that the perspective tool is the proper place (such an operation is not a change in perspective). The proper place, in my opinion, would be the curve bend filter itself (perhaps radio buttons to choose between applying the filter to the drawable, selection, or path, as is done for the Transform tools). Perhaps the idea has merit; however, it does bring up the issue of which other filters should have this same functionality. If the "Affect" parameter is not to be considered desirable for filters then an alternative option would be to make a "linear curve bend" TOOL so that the "Affect" option is available. Personally, I do not think that a new tool would be a good idea (it would create toolbox bloat for a limited application); adding an "Affect" option to filters might be worthwhile but it seems almost a philosophical issue and would require a case-by-case study of filters to determine if it makes sense for the filter to act on selections or paths (not to mention a great deal of work if a consistent approach is to be maintained). Then again, maybe I have completely misconstrued this report?
Saulgoode have said it very well. Initially I have choosen the perspective tool, because of the fact it works with image accurately, author have exact knowledge about the position of corners (with "curve bend" it isn't so). Second, if we have "linear curve bend", it could be divided in to the several transformations, of parts of picture, which are exactly filling of tetragon without applying the linear perspective (the type of transformation we are talking about). And also (only theoretically) the perspective tool can be imagined as filling the tetragon with the picture and then applying the 'perspective effect', if we forget on transformation matrix behind them. Probably it is only my personal crazy understanding/view. But... In my opinion - possible way could be to add possibility to switch off the linear perspective in perspective tool. I know it seems to be contradiction (turn off perspective in perspec. tool), but only on the level of labeling the tool. I choose the perspec. tool only for the fact it handles with corners of image independently, in opposite to others transform tools.
What I forget to add: The "curve bend" affect the image only 'in one dimension' - change the top and bottom profile/edge. But imagine you get the picture and you can freely move with corners and deform it in greater amount. That is, what I'm talking about. I know the attached picture doesan't show it very well - there are changed only top and bottom edges, but left and right could also be changed (simultaneously). And that could be faster then applying the "linear curve bend" two times - ones in vertical direction and second in horizontal.
This tool can be named "Distort" where the distortion can be either vertical (the four nodes move only vertical )or horizontal (the four nodes move only horizontally). Thus the algorithm is simple : scale individual lines seperately. and then probably antialias.
This might be something one of our current transform tools can do by now.
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