2.2 Displaying bitmaps on the screen
make-bitmap to create a bitmap of the specified dimensions:(setq *bitmap* (make-bitmap :width 100 :height 100))To draw a line on the newly created bitmap, enter the following expression:
(draw-line *bitmap* (make-position 0 0) (make-position 100 100))The line drawn on
*bitmap* is not visible because*bitmap* must be associated with a viewport or a window to be seen on the display, as in the following example:
(setq *viewport1*
(make-viewport :bitmap *bitmap* :width 100 :height 100))
You now see a diagonal line on the screen where*viewport1* maps*bitmap* onto the screen. Though you used a viewport in this example, you could have used a window instead to map*bitmap* onto the screen. Since*bitmap* is already mapped onto the screen, anything you draw on it shows on the screen immediately:
(draw-circle *bitmap* (make-position 50 50) 30)Viewports do not automatically associate bitmap output streams with their bitmaps. Thus, to format text onto
*bitmap*, you must associate a bitmap output stream with the bitmap, as in the following example:
(setq *bitmap-output-stream*
(make-bitmap-output-stream :bitmap *bitmap*))
(format *bitmap-output-stream* "ABC 123")
There are other ways of sending text to a bitmap that do not require creating a bitmap output stream; see Section 2.2.4 on page 19 for more information.
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