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Create an image in PHP to show guitar chords

Posted by: admin April 23, 2020 Leave a comment

Questions:

I have a site that shows guitar chords/tabs in text format. Here’s what I am currently displaying:

Em:

| | | | | |
| | | | | |
| 2 2 | | |
| | | | | |
| | | | | |

I learn that GD can create a dynamic image for this. But I am new at PHP and I have no idea what to do.

Is it simple to create such thing in PHP to display an image?

Thanks

How to&Answers:

First download the arial font and get this image (save as guitar.jpg):

guitar.jpg

and put them in the same folder as this script (for example chords.php):

<?php

  function showChord($chord) {
    $imgfile = "./guitar.jpg";
    $text = ".";
    $font = './arial.ttf';

    $im = imagecreatefromjpeg($imgfile);
    $x = imagesx($im);
    $y = imagesy($im);
    $fontsize = 100;
    $white = imagecolorallocate($im, 0, 0, 0);

    $chords = explode('-', $chord);
    // chords[0] = e1 and chords[5] = e6

    $minimum = min($chords);
    imagettftext($im, 15, 0, 1, 32, $white, $font, $minimum);
    $add = 0;
    if($minimum > 0) {
      $add = 30;  
    }
    // chords positions
    $interval1 = ($chords[0] != 0 ? (25 + $add + (intval($chords[0]) - $minimum) * 30) : 0);
    $interval2 = ($chords[1] != 0 ? (25 + $add + (intval($chords[1]) - $minimum) * 30) : 0);
    $interval3 = ($chords[2] != 0 ? (25 + $add + (intval($chords[2]) - $minimum) * 30) : 0);
    $interval4 = ($chords[3] != 0 ? (25 + $add + (intval($chords[3]) - $minimum) * 30) : 0);
    $interval5 = ($chords[4] != 0 ? (25 + $add + (intval($chords[4]) - $minimum) * 30) : 0);
    $interval6 = ($chords[5] != 0 ? (25 + $add + (intval($chords[5]) - $minimum) * 30) : 0);
    // write to the image
    imagettftext($im, $fontsize, 0, 01, $interval1, $white, $font, $text);
    imagettftext($im, $fontsize, 0, 18, $interval2, $white, $font, $text);
    imagettftext($im, $fontsize, 0, 36, $interval3, $white, $font, $text);
    imagettftext($im, $fontsize, 0, 53, $interval4, $white, $font, $text);
    imagettftext($im, $fontsize, 0, 70, $interval5, $white, $font, $text);
    imagettftext($im, $fontsize, 0, 86, $interval6, $white, $font, $text);
    header("Content-type: image/jpeg");
    imagejpeg($im);
    ImageDestroy($im);
  }

#  $chord = '0-2-2-0-0-0'; //Em
  $chord = '2-4-4-3-2-2'; //F#
  showChord($chord);

This will ouput something like for F#. The 2 on the top left means the second fret:

enter image description here

**note: I would also save the image to the disk so you don’t have to regenerate the same tab over and over.*

Answer:

Tony Pottier has written a beautiful class just to do this. http://www.tonypottier.info/

Edit: to solve the problem as mentioned below:

$c = new chord(array('x',13,12,11,12,'x'));
$c->setMarginRight(20);
$c->setStartingFret(10);
$c->draw();

Without the margin-right double-figured fretnumbers won’t show correctly.