How to wrap text written on an image with the GD library

Question

How can I use the PHP image generation functions to place long text over an image, choosing an area, a horizontal alignment, a vertical alignment, and letting long text word wrap correctly in the chosen area?

Can this be replicated and become useful in other languages?

Answer 1

PHP function imagettftext(...) can write text but does not support wrapping of long text, so you must divide the text in words, and for each word call imagettfbbox(...) to calculate the word boundary and test if the word should go on a new line.

To be able to vertical align the text you must defer rendering till the end, when you know the total height of the text.

Here is the code.

DEMO USAGE

<?php


// Image params

    $imgWidth = 240;
    $imgHeight = 900;


// Text params

    $text='Tanto va la gatta al lardo che ci lascia lo zampino!';
    $drawFrame=array(10,340,$imgWidth-10,$imgHeight-140);
    $fontType = 'ArialBlack.ttf';
    $fontSize = 30;
    $lineHeight=32;
    $wordSpacing=' ';
    $hAlign=0; // -1:left  0:center 1:right
    $vAlign=0; // -1:top  0:middle 1:bottom


// allocate

    $img = imagecreatetruecolor($imgWidth,$imgHeight);
    $background = imagecolorallocate($img, 78,129,154);
    $textColor = imagecolorallocate($img, 255,255,255);

// debug show text area

    $area_color = imagecolorallocate($img, 255,0,0);
    imagerectangle ($img, $drawFrame[0], $drawFrame[1], $drawFrame[2], $drawFrame[3], $area_color);

// write text

    wrapimagettftext($img, $fontSize, $drawFrame, $textColor,$fontType, $text, '100%',' ',$hAlign,$vAlign);

// output image

    header("Content-type: image/png");
    imagepng($img);
    imagecolordeallocate($img, $textColor );
    imagecolordeallocate($img, $background );

?>

THE MAIN FUNCTION

<?php


function wrapimagettftext($img, $fontSize, $drawFrame, $textColor,$fontType, $text, $lineHeight='',$wordSpacing='',$hAlign=0,$vAlign=0) {

    if($wordSpacing===' ' || $wordSpacing==='') {
        $size = imagettfbbox($fontSize, 0, $fontType, ' ');
        $wordSpacing=abs($size[4]-$size[0]);
    }
    $size = imagettfbbox($fontSize, 0, $fontType, 'Zltfgyjp');
    $baseHeight=abs($size[5]-$size[1]);
    $size = imagettfbbox($fontSize, 0, $fontType, 'Zltf');
    $topHeight=abs($size[5]-$size[1]);

    if($lineHeight==='' || $lineHeight==='') {
        $lineHeight=$baseHeight*110/100;
    } else if(is_string($lineHeight) && $lineHeight{strlen($lineHeight)-1}==='%') {
        $lineHeight=floatVal(substr($lineHeight,0,-1));
        $lineHeight=$baseHeight*$lineHeight/100;
    } else {

    }

    $usableWidth=$drawFrame[2]-$drawFrame[0];
    $usableHeight=$drawFrame[3]-$drawFrame[1];

    $leftX=$drawFrame[0];
    $centerX=$drawFrame[0]+$usableWidth/2;
    $rightX=$drawFrame[0]+$usableWidth;

    $topY=$drawFrame[1];
    $centerY=$drawFrame[1]+$usableHeight/2;
    $bottomY=$drawFrame[1]+$usableHeight;

    $text = explode(" ", $text);

    $line_w=-$wordSpacing;
    $line_h=0;
    $total_w=0;
    $total_h=0;
    $total_lines=0;

    $toWrite=array();
    $pendingLastLine=array();

    for($i=0;$i<count($text);$i++) {
        $size = imagettfbbox($fontSize, 0, $fontType, $text[$i]);

        $width = abs($size[4] - $size[0]);
        $height = abs($size[5] - $size[1]);

        $x = -$size[0]-$width/2;
        $y = $size[1]+$height/2;

        if($line_w+$wordSpacing+$width>$usableWidth) {
            $lastLineW=$line_w;
            $lastLineH=$line_h;

            if($total_w<$lastLineW) $total_w=$lastLineW;
            $total_h+=$lineHeight;

            foreach($pendingLastLine as $aPendingWord) {

                if($hAlign<0) $tx=$leftX+$aPendingWord['tx'];
                else if($hAlign>0) $tx=$rightX-$lastLineW+$aPendingWord['tx'];
                else if($hAlign==0) $tx=$centerX-$lastLineW/2+$aPendingWord['tx'];

                $toWrite[]=array('line'=>$total_lines,'x'=>$tx,'y'=>$total_h,'txt'=>$aPendingWord['txt']);
            }
            $pendingLastLine=array();

            $total_lines++;
            $line_w=$width;
            $line_h=$height;

            $pendingLastLine[]=array('tx'=>0,'w'=>$width,'h'=>$height,'x'=>$x,'y'=>$y,'txt'=>$text[$i]);
        } else {

            $line_w+=$wordSpacing;
            $pendingLastLine[]=array('tx'=>$line_w,'h'=>$width,'w'=>$height,'x'=>$x,'y'=>$y,'txt'=>$text[$i]);
            $line_w+=$width;
            if($line_h<$height) $line_h=$height;
        }
    }

    $lastLineW=$line_w;
    $lastLineH=$line_h;

    if($total_w<$lastLineW) $total_w=$lastLineW;
    $total_h+=$lineHeight;

    foreach($pendingLastLine as $aPendingWord) {

        if($hAlign<0) $tx=$leftX+$aPendingWord['tx'];
        else if($hAlign>0) $tx=$rightX-$lastLineW+$aPendingWord['tx'];
        else if($hAlign==0) $tx=$centerX-$lastLineW/2+$aPendingWord['tx'];

        $toWrite[]=array('line'=>$total_lines,'x'=>$tx,'y'=>$total_h,'txt'=>$aPendingWord['txt']);
    }
    $pendingLastLine=array();
    $total_lines++;

    $total_h+=$lineHeight-$topHeight;

    foreach($toWrite as $aWord) {

        $posx = $aWord['x'];

        if($vAlign<0) $posy=$topY+$aWord['y'];
        else if($vAlign>0) $posy=$bottomY-$total_h+$aWord['y'];
        else if($vAlign==0) $posy=$centerY-$total_h/2+$aWord['y'];

        imagettftext($img, $fontSize, 0, $posx, $posy , $textColor, $fontType, $aWord['txt']);

    }
}
?>