boundingBoxPreservingAspectRatioXmidYmid method

void boundingBoxPreservingAspectRatioXmidYmid(Box box, Rect rect)

Box is interpreted as a proportion, with 100 being the highest unit value.

• Tip: Set the aspect ratio of this Rect before calling this method,
• which is done by setting the height to 1.0 and the width to the aspect ratio.

Implementation

void boundingBoxPreservingAspectRatioXmidYmid(Box box, Rect rect)
{
  double aspectRatioBefore = toSize().aspectRatio();

  // Compute size based on box which will contain rect within space defined by box.
  width = (rect.width * 100.0) / (100.0 - (box.left + box.right) );
  height = (rect.height * 100.0) / (100.0 - (box.top + box.bottom) );

  // Initial position.
  left = rect.left;
  top = rect.top;

  // Compute position from box such that box contains rect.
  left -= (box.left/100.0) * width;
  top -= (box.top/100.0) * height;

  // Correction for aspect ratio. This is necessary because we may be given Box.ZERO_BOX, which won't match aspect ratio.
  // We must gracefully handle this so we can get a good initial state.
  double aspectRatio = toSize().aspectRatio();

  if (aspectRatio > aspectRatioBefore) {
    double oldHeight = height;
    height = width * (1/aspectRatioBefore);
    // Adjust position so as to center (XmidYMid).
    top -= 0.5 * ( (height - oldHeight) / height ) * height;
  }
  else if (aspectRatio < aspectRatioBefore) {
    double oldWidth = width;
    width = height * aspectRatioBefore;
    // Adjust position so as to center (XmidYMid).
    left -= 0.5 * ( (width - oldWidth) / width ) * width;
  }
}