I figured out a way to use some lessons from the past. If you have to rotate a photograph, just find a line that should be either horizontal or verticle. Crop the image so that the line goes from one corner to the next and remember the pixel width and height of the crop. Then simple take the arctan of the width/height to get the number of degrees you need to rotate (depending on how you cropped, you may have to subtract your answer from 90, it should be pretty obvious unless you are tilted by ~45 degrees)
Also, if you have Excel, just enter
=DEGREES(ATAN(w/h))
where w and h are the width and height respectively.
Try this one...
Select the "measure" tool (Rigth-click on the eyedropper, select the ruler), then drag along the line that should be vertical or horizontal. Now immediately select image/rotate canvas/arbitrary and voila, the correct rotation is entered for you.
I usually just draw out the cropping rectangle, put one edge next to the element I'm aligning with, and rotate the crop box until that side is parallel to the specified element. I then drag out the crop box to cover the area I want.
One advantage of this method is I can choose to under- or over-correct the rotation if I see another important element will be lost in the crop if rotated "properly."
In PSP Ctrl+Alt+G puts up a grid, then you just rotate to match the grid. Might take a couple of attempts and undoings, but still quicker than the maths approach.
I usually just draw out the cropping rectangle, put one edge next to the element I'm aligning with, and rotate the crop box until that side is parallel to the specified element. I then drag out the crop box to cover the area I want.
One advantage of this method is I can choose to under- or over-correct the rotation if I see another important element will be lost in the crop if rotated "properly."
Paul, thanks for that! Can you believe I never knew you could rotate the crop box??!! LOL, you learn something new every day.
