3. The method according to claim 2 , wherein the rasterizing in the view window an element which the annotations avoid comprises: analyzing an avoidance type of the element which the annotations avoid, and if the avoidance type is annotation overlying forbidden, assigning 1 to a bit for identifying annotation overlying forbidden in each of respective pixel values of pixels that correspond to the element which the annotations avoid and are to be plotted when the element which the annotations avoid is displayed in the view window; if the avoidance type is avoid overlying if permitted, assigning 1 to a bit for identifying avoid overlying if permitted in each of respective pixel values of pixels that correspond to the element which the annotation avoids and are to be plotted when the element which the annotation avoids is displayed in the view window.
3. The method according to claim 2 , wherein the rasterizing in the view window an element which the annotations avoid comprises: analyzing an avoidance type of the element which the annotations avoid, and if the avoidance type is annotation overlying forbidden, assigning 1 to a bit for identifying annotation overlying forbidden in each of respective pixel values of pixels that correspond to the element which the annotations avoid and are to be plotted when the element which the annotations avoid is displayed in the view window; if the avoidance type is avoid overlying if permitted, assigning 1 to a bit for identifying avoid overlying if permitted in each of respective pixel values of pixels that correspond to the element which the annotation avoids and are to be plotted when the element which the annotation avoids is displayed in the view window. 4. The method according to claim 3 , wherein the preset display condition is, in the pixel values of pixels within the plane annotation region, the bits for identifying annotation overlying forbidden are all zeros (0s), and the number of ones (1s) of the bits for identifying avoid overlying if permitted is minimum.