/**
* Compute the caption area.
*/
private function computeCaptionArea()
{
$graphUnpaddedRight = $this->imageArea->x1 + ($this->imageArea->x2 - $this->imageArea->x1) * $this->graphCaptionRatio + $this->graphPadding->left + $this->graphPadding->right;
$titleUnpaddedBottom = $this->imageArea->y1 + $this->titleHeight + $this->titlePadding->top + $this->titlePadding->bottom;
$captionArea = new Rectangle($graphUnpaddedRight, $titleUnpaddedBottom, $this->imageArea->x2, $this->imageArea->y2);
$this->captionArea = $captionArea->getPaddedRectangle($this->captionPadding);
}
