PHP GD imagettftext measurements - php

Question

I'm trying to write a script that generates a PNG image from the text, size and the font it gets in the $_GET arguments, but I can't figure out how to make size of the image fit exactly to the text. I'm already using imagettfbox:
$widthPx = abs($ttfBox[2] - $ttfBox[0]);
$heightPx = abs($ttfBox[1] - $ttfBox[7]);
which probably gives me the correct measurements but when I draw my text, it gets a little bit out of bounds. For example if I try to draw an "a" using arial.ttf its at least 5 pixels out of bounds. Is there a way to draw a text of any font exactly fitting to the image without testing out?
$text = $_GET["text"];
$cmToPixel = 15.0;
$sizeCm = floatval($_GET["sizeCm"]);
$sizePx = $cmToPixel * $sizeCm;
$fontFile = "fonts/".pathinfo($_GET["font"])["filename"].".".pathinfo($_GET["font"])["extension"];
if(!file_exists($fontFile)){
die;
}
$ttfBox = imagettfbbox($sizePx, 0, $fontFile, $text);
$widthPx = abs($ttfBox[2] - $ttfBox[0]);
$heightPx = abs($ttfBox[1] - $ttfBox[7]);
$image = ImageCreate($widthPx, $heightPx);
$x = $ttfBox[0] + (imagesx($image)-$ttfBox[4] )/ 2 - 0;
$y = $ttfBox[1] + (imagesy($image) / 2) - ($ttfBox[5] / 2) - 5;
ImageRectangle($image,0,0,imagesx($image),imagesy($image), ImageColorAllocate($image,255,255,255));
imagettftext($image, $sizePx,0,$x,$y, ImageColorAllocate($image, 0, 0, 0), $fontFile, $text);
header("Content-Type: image/png");
ImagePng($image);
ImageDestroy($image);

Answer 1

Your calculations from the bounding box are off. This works:
<?php
/*-
* $MirOS: www/mk/ttf2png,v 1.8 2016/11/02 16:16:26 tg Exp $
*-
* Copyright (c) 2009, 2016
* mirabilos <m#mirbsd.org>
*
* Provided that these terms and disclaimer and all copyright notices
* are retained or reproduced in an accompanying document, permission
* is granted to deal in this work without restriction, including un-
* limited rights to use, publicly perform, distribute, sell, modify,
* merge, give away, or sublicence.
*
* This work is provided "AS IS" and WITHOUT WARRANTY of any kind, to
* the utmost extent permitted by applicable law, neither express nor
* implied; without malicious intent or gross negligence. In no event
* may a licensor, author or contributor be held liable for indirect,
* direct, other damage, loss, or other issues arising in any way out
* of dealing in the work, even if advised of the possibility of such
* damage or existence of a defect, except proven that it results out
* of said person's immediate fault when using the work as intended.
*-
* Syntax:
* php ttf2png [text [size [/path/to/font.ttf]]] >out.png
*/
if (!function_exists('gd_info'))
die("Install php5-gd first.");
$gd = gd_info();
if ($gd["FreeType Support"] == false)
die("Compile php5-gd with FreeType 2 support.");
$font = "/usr/src/www/files/FNT/GenI102.ttf";
$fontsize = 30;
$text = "EINVAL";
if (isset($argv[1]))
$text = $argv[1];
if (isset($argv[2]))
$fontsize = $argv[2];
if (isset($argv[3]))
$font = $argv[3];
// Get bounding box
$bbox = imageftbbox($fontsize, 0, $font, $text);
// Transform coordinates into width+height and position
$ascender = abs($bbox[7]);
$descender = abs($bbox[1]);
$size_w = abs($bbox[0]) + abs($bbox[2]);
$size_h = $ascender + $descender;
$x = -$bbox[0];
$y = $ascender;
// Create image
$im = imagecreatetruecolor($size_w, $size_h);
// Allocate colours
$bgcol = imagecolorallocate($im, 0x24, 0x24, 0x24);
$fgcol = imagecolorallocate($im, 0xFF, 0xFF, 0xFF);
// Fill image with background colour
imagefilledrectangle($im, 0, 0, $size_w - 1, $size_h - 1, $bgcol);
// Render text into image
imagefttext($im, $fontsize, 0, $x, $y, $fgcol, $font, $text);
// Convert true colour image (needed for above) to palette image
imagetruecolortopalette($im, FALSE, 256);
// Output created image
imagepng($im, NULL, 9);
exit(0);
If you write multiple strings on the same line and need to calculate the total height and offset of the line, it’s the maximum of all ascenders plus the maximum of all descenders, and $y for all imagefttext calls for that line is similarily the maximum of all ascenders.