Unfortunately, i do not have php installed currently so can't test, but maybe following will work.
In image.class.php replace this
// Copy and resize part of an image with resampling
imagecopyresampled(
$ni, $im, // destination, source
0, 0, 0, 0, // dstX, dstY, srcX, srcY
$this->max_x, $this->max_y, // dstW, dstH
$orig_x, $orig_y); // srcW, srcH
with this
if ($orig_img_type == 3) {
imagealphablending($ni, false);
}
// Copy and resize part of an image with resampling
imagecopyresampled(
$ni, $im, // destination, source
0, 0, 0, 0, // dstX, dstY, srcX, srcY
$this->max_x, $this->max_y, // dstW, dstH
$orig_x, $orig_y); // srcW, srcH
if ($orig_img_type == 3) {
imagesavealpha($ni, true);
}