/**
* resize only content of an image keeping original canvas dimensions. "empty" parts will have $bgcolor. (constrained proportions)
* @param integer delta number of pixels to grow or shrink
* @param string background-color
* @param optional boolean set to true to allow image to grow
* @param optional string filter used to resize (grow) the image. Choose from Cubic, Quadratic, Gaussian, Bessel, Hamming, Mitchell, Triangle, Lanczos (default), Sinc, Catrom, Hermite, Hanning, Blackman, Point, Box
*/
function resizeContent($delta, $bgcolor, $allowgrow = false, $filter = "")
{
$tmp = new NXImageApi($this->tempfile, $this->tempfile, $this->debug);
$this->createCanvas($this->width(), $this->height(), $bgcolor);
$tmp->resizeAbsolute($tmp->width() + $delta, $tmp->height() + $delta, $allowgrow, $filter);
$gravity = isset($this->gravity) ? " -gravity {$this->gravity} " : "";
$this->_execute("composite {$gravity} -compose Over {$tmp->tempfile} {$this->tempfile} {$this->tempfile}");
$tmp->deltemp();
}
