The image size in pixels is stored in ImageSize. When the value of UseDpi is false, then then RealImageSize will be equal to ImageSize.
When UseDpi is true, then the image size to use is calculated by this formula:
Image size to use = ImageSize * ScreenDpi / ImageDpi
This value is stored in RealImageSize, which uses the formula above while making the necessary checks to use default values if ImageDpiX, ImageDpiY, ScreenDpiX or ScreenDpiY are not set.
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2