Tk_GetPixmap(display, d, width, height, depth)
These procedures are identical to the Xlib procedures XCreatePixmap and XFreePixmap, except that they have extra code to manage X resource identifiers so that identifiers for deleted pixmaps can be reused in the future. It is important for Tk applications to use these procedures rather than XCreatePixmap and XFreePixmap; otherwise long-running applications may run out of resource identifiers.
Tk_GetPixmap creates a pixmap suitable for drawing in d, with dimensions given by width, height, and depth, and returns its identifier. Tk_FreePixmap destroys the pixmap given by pixmap and makes its resource identifier available for reuse.