Hello again,
I've been playing around with lispbuilder-SDL a bit over the holiday
weekend and started writing a simple jigsaw puzzle-like game. I'm
very happy with what I have so far but I'm running into a bit of
slowness when doing direct pixel manipulation, specifically, rotating
images.
I've looked at rotozoom in the gfx package and I could not get it to
work (that's another issue altogether). Rotating an image seemed like
such a simple thing anyway, so I wrote my own
likely-over-complicated-and-bug-ridden function to do it:
(defun rotate-surface(surf degrees)
"rotates a surface 0, 90, 180, or 270 degrees"
(let ((degrees (normalize-degrees degrees)))
(if (= 0 degrees)
;; in the case of 0 degrees, just copy surface
(copy-and-blit-surface surf)
;; else do rotation
(let* ((w (surf-w surf))
(h (surf-h surf))
(new-w (if (or (= 90 degrees)
(= 270 degrees)) h w))
(new-h (if (or (= 90 degrees)
(= 270 degrees)) w h))
(new-surf (create-surface new-w new-h :surface surf))
(new-x (case degrees
(90 #'(lambda (x y)(declare (ignore x))(+ (1-
new-w) (- 0 y))))
(180 #'(lambda (x y)(declare (ignore y))(+ (1-
new-w) (- 0 x))))
(270 #'(lambda (x y)(declare (ignore x))y))))
(new-y (case degrees
(90 #'(lambda (x y)(declare (ignore y))x))
(180 #'(lambda (x y)(declare (ignore x))(+ (1-
new-h) (- 0 y))))
(270 #'(lambda (x y)(declare (ignore y))(+ (1-
new-h) (- 0 x)))))))
(loop :for x :from 0 :to (1- w)
:do (loop :for y :from 0 :to (1- h)
:do (let ((pixel (get-pixel :position (point x y)
:surface surf)))
(draw-pixel (funcall new-x x y)
(funcall new-y x y) :surface new-surf
:color (sdl:sdl_maprgb
(sdl:pixelformat sdl:*default-surface*)
(color-r pixel)
(color-g pixel)
(color-b pixel)))
#+nil(draw-point :position (point (funcall new-x x y)
(funcall new-y x y))
:surface new-surf
:color pixel))))
new-surf))))
The function works but the pixel access is very slow. It seems like I
need some way to directly access the surface memory, perhaps with a 2d
byte array? Maybe this is not possible with CFFI, or maybe the
solution is right under my nose and I'm not seeing it.
Any suggestions?
Thanks,
Anthony
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