#64 Incorrect positioning math using imageftbbox() and abs()?

[Kevin Colby]

In tracking down an unrelated problem with X axis title positioning, I starting looking at the text centering code used in pChart.class in many places. I reached the conclusion I think all the positioning math based on imageftbbox() output may be slightly wrong.

There are numerous examples of code of the form "abs($Position[2]) + abs($Position[0])". While this seems close most of the time, I think that's just by because the boxes used in this code are generally all positive and start close to zero, so this approximates simply saying "$Position[2]". What all examples of this should really be is of the form "abs($Position[2] - $Position[0])", first doing subtraction and then taking the absolute value of the result, since in theory, these positional values could be crossing the zero axis or be entirely negative, etc. There is some discussion of this mistake in general (not related to pChart specifically) on php.net in the imageftbbox function comments (http://php.net/manual/en/function.imageftbbox.php). If I'm mistaken on this however, please let me know. I just can't imagine how doing abs() individually and summing could possibly be what is really intended here.