message: fixed imshow on mac; before that just the window titlebar was shown, without the window content.
diff: @@ -230,7 +230,7 @@ CV_IMPL void cvShowImage( const char* name, const CvArr* arr)
  if (oldImageSize.height != imageSize.height || oldImageSize.width != imageSize.width)
  {
  //Set new view size considering sliders (reserve height and min width)
  - NSSize scaledImageSize;
  + NSSize scaledImageSize = imageSize;
  if ([[window contentView] respondsToSelector:@selector(convertSizeFromBacking:)])
  {
  // Only resize for retina displays if the image is bigger than the screen
  @@ -239,13 +239,14 @@ CV_IMPL void cvShowImage( const char* name, const CvArr* arr)
  screenSize.height -= titleBarHeight;
  if (imageSize.width > screenSize.width || imageSize.height > screenSize.height)
  {
  + CGFloat fx = screenSize.width/std::max(imageSize.width, (CGFloat)1.f);
  + CGFloat fy = screenSize.height/std::max(imageSize.height, (CGFloat)1.f);
  + CGFloat min_f = std::min(fx, fy);
  scaledImageSize = [[window contentView] convertSizeFromBacking:imageSize];
  + scaledImageSize.width = std::min(scaledImageSize.width, min_f*imageSize.width);
  + scaledImageSize.height = std::min(scaledImageSize.height, min_f*imageSize.height);
  }
  }
  - else
  - {
  - scaledImageSize = imageSize;
  - }
  NSSize contentSize = vrectOld.size;
  contentSize.height = scaledImageSize.height + [window contentView].sliderHeight;
  contentSize.width = std::max<int>(scaledImageSize.width, MIN_SLIDER_WIDTH);
  @@ -735,6 +736,7 @@ void cv::setWindowTitle(const String& winname, const String& title)
  static NSSize constrainAspectRatio(NSSize base, NSSize constraint) {
  CGFloat heightDiff = (base.height / constraint.height);
  CGFloat widthDiff = (base.width / constraint.width);
  + if (heightDiff == 0) heightDiff = widthDiff;
  if (widthDiff == heightDiff) {
  return base;
  }
  