PHP GD ttftext center alignment

Question

I'm using imagettftext to make a bar graph and at the top of each bar I want to put the value.

I have the following variables for each bar (which are really rectangles)

$x1 $y1 $x2 $y2 $imagesx $imagesy $font_size

Also, The fontsize should decrease as the string length increases.

Answer 1

Do it like this. Remember to place the font file "arial.ttf" in current directory:

<?php
// Create a 650x150 image and create two colors
$im = imagecreatetruecolor(650, 150);
$white = imagecolorallocate($im, 255, 255, 255);
$black = imagecolorallocate($im, 0, 0, 0);

// Set the background to be white
imagefilledrectangle($im, 0, 0, 649, 149, $white);

// Path to our font file
$font = './arial.ttf';

//test it out
for($i=2;$i<10;$i++)
    WriteTextForMe($im, $font, str_repeat($i, $i), -140 + ($i*80), 70 + rand(-30, 30), -160 + (($i+1)*80), 150, $black);

//this function does the magic
function WriteTextForMe($im, $font, $text, $x1, $y1, $x2, $y2, $allocatedcolor)
{
    //draw bars
    imagesetthickness($im, 2);
    imagerectangle($im, $x1, $y1, $x2, $y2, imagecolorallocate($im, 100,100,100));

    //draw text with dynamic stretching
    $maxwidth = $x2 - $x1;
    for($size = 1; true; $size+=1)
    {
        $bbox = imagettfbbox($size, 0, $font, $text);
        $width = $bbox[2] - $bbox[0];
        if($width - $maxwidth > 0)
        {
            $drawsize = $size - 1;
            $drawX = $x1 + $lastdifference / 2;
            break;
        }
        $lastdifference = $maxwidth - $width;
    }
    $size--;
    imagettftext($im, $drawsize, 0, $drawX, $y1 - 2, $allocatedcolor, $font, $text);
}

// Output to browser
header('Content-type: image/png');

imagepng($im);
imagedestroy($im);
?>

It uses imagettfbbox function to get width of the text, then loops over the font size to get correct size, centers it and displays it.

So, it outputs the following:

Answer 2

You can calculate the center of your text by using PHP's imagettfbbox-function:

// define text and font
$text = 'some bar label';
$font = 'path/to/some/font.ttf';

// calculate text size (this needs to be adjusted to suit your needs)
$size = 10 / (strlen($text) * 0.1);

// calculate bar center
$barCenter = $x1 + ($x2 - $x1) / 2;

// calculate text position (centered)
$bbox = imagettfbbox($size, 0, $font, $text);
$textWidth = $bbox[2] - $bbox[0];
$positionX = $textWidth / 2 + $barCenter;
$positionY = $y1 - $size;

EDIT: Updated the code to do all the work for you.