| 摘要 |
Methods and apparatus for capturing images on screens which display multiple windows. Exemplary embodiments eliminate unnecessary reading and writing of information pertaining to display data that is not visible. A user designates an arbitrary region of a screen to be captured, which can cross windows that are displayed at different layers within the image. A snapshot of the selected region is obtained by retrieving data for each of the pixels in the region, converting them into standard values, and storing them in an off-screen pixel map. Before the data for the pixels is obtained, a listing is made of all windows that are encompassed by the designated region. For each window a record is made of the portion of the window that is visible within the designated region. If no portion is visible, the window is removed from the list. After all of the windows within the region have been examined in this manner, only the pixels pertaining to the recorded visible portion of each window need to be read and stored in the pixel map. With this approach, redundancy is eliminated, since only the visible pixel data is retrieved and written to the pixel map. |
