More general affine transformations

[Houska1]

Thank you for this useful georeferencing tool.

Have you considered adding more general affine transformations? I recognize you are limited by QPainter but I see that QPainter::setWorldMatrix and QPainter::shear do offer additional flexibility beyond translate, rotate, xscale, yscale. Not sure if that is helpful.

A more general affine/perspective ability would be super useful for georeferencing UAV/drone photos in particular. Especially a "4 pt" mode defining an affine transformation of the image with different scale on its front and back edge (arising from UAV/gimbal pitch) plus skew (that may arise from UAV roll).

Thanks, Martin

[gvellut]

Thank you for your feedback.

Indeed, Qt allows a general affine transformation easily enough and adding it to the plugin should be pretty straightforward I think, using the existing tools as a model:

• A tool for shearing would need to be added.
• Also the 2 Point tool would need to be replaced with a 4 point tool (or I think 3 points would be sufficient?), with maybe some modifier for restricting to 2 points.

Possibly I will implement it myself (I cannot promise a completion date though...) but I am open to a contribution.