Feature Request: flexing compensation

[vnp85]

Context: as scanning progresses, flexing may happen, shifting the targeted line, from end to end, by a few pixels. The result is that flexing overcomes the doppler of the Sun's rotation. This is obvious when the p angle is high, but fools the user when the sun's equator aligns with the equatorial grid.

A possible countermeasure could be to let the user declare a linear slope by which the image is estimated, by the user, to have shifted from the beginning till the end of the scan. This would affect the constant d in the polynomial, as a function of frame index, ax3 + bx2 + cx+ d,

d' = d + (frameIndex relative to disk center) * slope

Thank you for considering