Why do imagettfbbox coordinates change when angle changes?

Hi,

I'm using php 4.4.4. Maybe I'm misreading the docs, but in the
imagettfbbox manual (http://us2.php.net/imagettfbbox), it says that
text coordinates are the same regardless of what the angle is.  But I
am getting two distinct sets of coordinates if I change the angle from
zero to 270.

Here's the relevant code:

$text = "hello";
$s = getImageSize($img_file);
$imgWidth = $s[0];
$imgHeight = $s[1];
$source=ImageCreateFromJPEG($img_file);
$size=16;
 $black=imagecolorallocate($source,0,0,0)
;
$font='/usr/share/fonts/msttcorefonts/times.ttf';
 $bbox=imagettfbbox($size,$angle,$font,$t
ext);
$textWidth=$bbox[2]-$bbox[0];
$textHeight=$bbox[5]-$bbox[3];
$x=($imgWidth/2)-($textWidth/2);
$y=($imgHeight/2)-($textHeight/2);
 imagettftext($source,$size,$angle,$x,$y,
$black,$font,$text );
header("Content-type: image/jpeg");

When I print out the bbox with 0, I get

Array ( [0] => -3 [1] => -1 [2] => 41 [3] => -1 [4] => 41 [5] => -16
[6] => -3 [7] => -16 )

with 270, I get

Array ( [0] => -13 [1] => -1 [2] => -13 [3] => 41 [4] => -1 [5] => 41
[6] => -1 [7] => -1 )

I must be misinterpreting the docs.  Why are the coordinates
different? - Dave

On Thu, 13 Mar 2008 18:18:13 +0100, laredotornado@zipmail.com  =

<laredotornado@zipmail.com> wrote:
> I'm using php 4.4.4. Maybe I'm misreading the docs, but in the
> imagettfbbox manual (http://us2.php.net/imagettfbbox), it says that
> text coordinates are the same regardless of what the angle is.

Nope

> But I
> am getting two distinct sets of coordinates if I change the angle from=

> zero to 270.
>
> Here's the relevant code:
>
>         $text =3D "hello";
>         $s =3D getImageSize($img_file);
>         $imgWidth =3D $s[0];
>         $imgHeight =3D $s[1];
>          $source=3DImageCreateFromJPEG($img_file)
;
>         $size=3D16;
>          $black=3Dimagecolorallocate($source,0,0,
0);
>         $font=3D'/usr/share/fonts/msttcorefonts/times.ttf';
>          $bbox=3Dimagettfbbox($size,$angle,$font,
$text);
>         $textWidth=3D$bbox[2]-$bbox[0];
>         $textHeight=3D$bbox[5]-$bbox[3];
>         $x=3D($imgWidth/2)-($textWidth/2);
>         $y=3D($imgHeight/2)-($textHeight/2);
>          imagettftext($source,$size,$angle,$x,$y,
$black,$font,$text );
>         header("Content-type: image/jpeg");
>
> When I print out the bbox with 0, I get
>
> Array ( [0] =3D> -3 [1] =3D> -1 [2] =3D> 41 [3] =3D> -1 [4] =3D> 41 [5=
] =3D> -16
> [6] =3D> -3 [7] =3D> -16 )
>
> with 270, I get
>
> Array ( [0] =3D> -13 [1] =3D> -1 [2] =3D> -13 [3] =3D> 41 [4] =3D> -1 =
[5] =3D> 41
> [6] =3D> -1 [7] =3D> -1 )
>
> I must be misinterpreting the docs.  Why are the coordinates
> different? - Dave

"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."

Which means that with normal text without an angle, you have this box wi=
th  =

the array-indexes:
6,7---------4,5
|           |
0,1---------2,3

However, if you have an angle of 180 (text upside down), you see this  =

picture:
2,3---------0,1
|           |
4,5---------6,7

So, 0 & 1 hold the 'lower left corner IF you see the text horizontally' =
as  =

opposed to the 'lower left corner if you look at the picture'. The  =

coordinates WILL change if the angele changes (how could they not?), but=
=

the different indexes will be for the same relative position from the te=
xt  =

if you were to look at the image the way the text appears horizontal  =

again.  (Damned, this is far more easily explained face-to-face by just =
=

rotating a piece of paper...).
-- =

Rik Wasmus

Greetings, Rik Wasmus.
In reply to Your message dated Thursday, March 13, 2008, 21:31:59,

> (Damned, this is far more easily explained face-to-face by just
> rotating a piece of paper...).

QFT :D

Thanks BTW, I was about to use this function myself and You just saved me ti
me
to uncover this info by my own trials and errors.


--
Sincerely Yours, AnrDaemon <anrdaemon@freemail.ru>