Import L1 (celery) as l1/

l1/sexp_effects/effects/crt.sexp

@@ -0,0 +1,30 @@
+;; CRT effect - old monitor simulation
+(require-primitives "image")
+
+(define-effect crt
+  :params (
+    (line_spacing :type int :default 2 :range [1 10])
+    (line_opacity :type float :default 0.3 :range [0 1])
+    (vignette_amount :type float :default 0.2)
+  )
+  (let* ((w (image:width frame))
+         (h (image:height frame))
+         (cx (/ w 2))
+         (cy (/ h 2))
+         (max-dist (sqrt (+ (* cx cx) (* cy cy)))))
+    (map-pixels frame
+      (lambda (x y c)
+        (let* (;; Scanline darkening
+               (scanline-factor (if (= 0 (mod y line_spacing))
+                                    (- 1 line_opacity)
+                                    1))
+               ;; Vignette
+               (dx (- x cx))
+               (dy (- y cy))
+               (dist (sqrt (+ (* dx dx) (* dy dy))))
+               (vignette-factor (- 1 (* (/ dist max-dist) vignette_amount)))
+               ;; Combined
+               (factor (* scanline-factor vignette-factor)))
+          (rgb (* (red c) factor)
+               (* (green c) factor)
+               (* (blue c) factor)))))))