It is possible to move the origin and also reverse the direction.
ie. you can make the top-left corner the origin and have positive
coordinates indicate down and to the right using something like this:
<?php
$p = PDF_new();
PDF_open_file($p);
PDF_set_info($p,"Creator","coords.php");
PDF_set_info($p,"Author","Rasmus Lerdorf");
PDF_set_info($p,"Title","Coordinate Test (PHP)");
PDF_begin_page($p,595,842);
PDF_translate($p,0,842); // Move Origin
PDF_scale($p, 1, -1); // Reflect across horizontal axis
PDF_set_value($p,"horizscaling",-100); // Mirror
$font = PDF_findfont($p,"Helvetica-Bold","host",0);
PDF_setfont($p,$font,-38.0);
PDF_show_xy($p, "Top Left", 10, 40);
PDF_end_page($p);
PDF_set_parameter($p, "openaction", "fitpage");
PDF_close($p);
$buf = PDF_get_buffer($p);
$len = strlen($buf);
Header("Content-type:application/pdf");
Header("Content-Length:$len");
Header("Content-Disposition:inline; filename=coords.pdf");
echo $buf;
PDF_delete($p);
?>
