Introduction - If you have any usage issues, please Google them yourself
In Windows applications, as long as for graphics, it is necessary to use the GDI Coordinate System. Windows provides several mapping methods, each of which corresponds with a map coordinate system. For example, graphics rendering, the graphics must be given in various areas in the customer location, the location of the two with x and y coordinates, x that the abscissa, y that the longitudinal coordinates. In all GDI drawing function, which coordinates the use of a " logical unit." When the GDI output function to the results when a physical device, Windows will be the logical coordinates into device coordinates (such as screen or printer pixels)