Emily Emily - 2 months ago 32
PHP Question

imagecreatefrompng() Makes a black background instead of transparent?

I make thumbnails using PHP and GD library but my code turn png transparency into a solid black color, Is there a solution to improve my code?

this is my php thumbnail maker code:

function cropImage($nw, $nh, $source, $stype, $dest) {
$size = getimagesize($source);
$w = $size[0];
$h = $size[1];

switch($stype) {
case 'gif':
$simg = imagecreatefromgif($source);
break;
case 'jpg':
$simg = imagecreatefromjpeg($source);
break;
case 'png':
$simg = imagecreatefrompng($source);
break;
}

$dimg = imagecreatetruecolor($nw, $nh);
$wm = $w/$nw;
$hm = $h/$nh;
$h_height = $nh/2;
$w_height = $nw/2;

if($w> $h) {
$adjusted_width = $w / $hm;
$half_width = $adjusted_width / 2;
$int_width = $half_width - $w_height;
imagecopyresampled($dimg,$simg,-$int_width,0,0,0,$adjusted_width,$nh,$w,$h);
} elseif(($w <$h) || ($w == $h)) {
$adjusted_height = $h / $wm;
$half_height = $adjusted_height / 2;
$int_height = $half_height - $h_height;

imagecopyresampled($dimg,$simg,0,-$int_height,0,0,$nw,$adjusted_height,$w,$h);
} else {
imagecopyresampled($dimg,$simg,0,0,0,0,$nw,$nh,$w,$h);
}

imagejpeg($dimg,$dest,100);
}


Thank you

Answer

After imagecreatetruecolor():

<?php

// ... Before imagecreatetruecolor()

$dimg = imagecreatetruecolor($width_new, $height_new); // png ?: gif

// start changes
switch ($stype) {

    case 'gif':
    case 'png':
        // integer representation of the color black (rgb: 0,0,0)
        $background = imagecolorallocate($dimg , 0, 0, 0);
        // removing the black from the placeholder
        imagecolortransparent($dimg, $background);

    case 'png':
        // turning off alpha blending (to ensure alpha channel information
        // is preserved, rather than removed (blending with the rest of the
        // image in the form of black))
        imagealphablending($dimg, false);

        // turning on alpha channel information saving (to ensure the full range
        // of transparency is preserved)
        imagesavealpha($dimg, true);
        break;

    default:
        break;
}
// end changes

$wm = $w/$nw;
$hm = $h/$nh;

// ...