Hi. I have 2 points in a UIView, but I am unable to get the correct line equation between these two points because UIView coordinate system is not cartesian. When I apply the cartesian slope of a line, I keep getting the wrong slope for the UIView coordinate system. Maybe I'm applying the identity matrix incorrectly or using the wrong identity matrix. Do I need to translate the point-slope form equation too? I'm not sure. Any help would be greatly appreciated.
A:
Are you getting the wrong slope because the CG coordinate system is flipped/mirrored upside-down between the iPhone and Mac OS? If so then just change dy to -dy in your slope equation.
hotpaw2
2010-08-30 06:12:51
Thanks, but doesn't that only just make the slope negative of its current value? It doesn't seem to work for all instances. The iPhone screen is mirrored so y increases down instead of up like in cartesian. The problem is that the two points are in the iPhone coordinate system and I am unable to calculate the line that is formed by these two points. Whenever I apply the formula for a line, the answer is not always correct depending on the location of the points.
2010-08-30 06:40:29