PHP中的“imagettfbbox（）”如何工作？

Question

Could you please explain what exactly the return value of imagettfbbox() mean? The manual says:

imagettfbbox() returns an array with 8 elements representing four points making the bounding box of the text on success and FALSE on error. [...Table of points here...] The points are relative to the text regardless of the angle, so "upper left" means in the top left-hand corner seeing the text horizontally.

But, I found it not very clear. For example, the return value:

array(-1, 1, 61, 1, 61, -96, -1, -96)

means the following points:

(-1, -96) ------ (61, -96)
    |                |
    |                |
    |                |
    |                |
    |                |
    |                |
 (-1, 1) -------- (61, 1)              

How should I interpret them?

Why there are negative values?

Answer 1

The following resource explains this: http://www.tuxradar.com/practicalphp/11/2/6

Just use abs(). This is from the resource above: "[the function] returns its values from the lower-left corner of the baseline of the text string, not the absolute lower-left corner. The baseline of a letter is where it would sit if you were hand writing it on lined paper"