// resize image
$image = Intervention\Image\Facades\Image::make(public_path() . '/template.png')
    ->resize(640, null, function ($constraint) {
        $constraint->aspectRatio();
    })
    ->save(public_path() . '/output.png')
    ->destroy();
// Fill transparent with white color
$image = Intervention\Image\Facades\Image::canvas(640, 527)
    // fill white to transparent on empty image
    ->fill('#fff')
    // fill image into empty image
    ->fill(public_path() . '/output.png')
    ->save(public_path() . '/output1.png')->destroy();

// Get the original image.
$src = imagecreatefrompng(public_path() . '/output1.png');

// Get the width and height.
$width = imagesx($src);
$height = imagesy($src);

// Create a white background, the same size as the original.
$bg = imagecreatetruecolor($width, $height);
$red = imagecolorallocate($bg, 255, 0, 0);
$white = imagecolorallocate($bg, 0, 0, 0);
imagefill($bg, 0, 0, $white);
$tr = imagecolortransparent($bg, $white);

// Merge the two images.
imagecopyresampled(
    $bg, $src,
    0, 0, 0, 0,
    $width, $height,
    $width, $height);
// (left, top, left + width, top + height)
imagefilledrectangle($bg, 37, 170, 603, 493, $tr);

// Save the finished image.
imagepng($bg, public_path() . '/merged.png', 0);