start of cx16 colorbars example

examples/cx16/colorbars.p8

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+%import gfx2
+%import palette
+%import textio
+
+
+; TODO WORK IN PROGRESS...
+; want to make Amiga 'copper' bars color cycling effects
+
+
+main {
+    sub start() {
+        palette.set_all_black()
+        gfx2.screen_mode(4)
+
+        ubyte yy
+        for yy in 0 to 239
+            gfx2.horizontal_line(0, yy, 320, yy & 63)
+
+        repeat {
+            colors.random_bar()
+            colors.set_palette()
+            repeat 20
+                sys.waitvsync()
+        }
+
+        repeat {
+        }
+    }
+
+}
+
+colors {
+    ubyte cr
+    ubyte cg
+    ubyte cb
+    ubyte[48+16] reds
+    ubyte[48+16] greens
+    ubyte[48+16] blues
+    ubyte bar_size
+
+    sub random_rgb12() {
+        do {
+            uword rr = rndw()
+            cr = msb(rr) & 15
+            cg = lsb(rr)
+            cb = cg & 15
+            cg >>= 4
+        } until cr+cg+cb >= 12
+    }
+
+    sub random_bar() {
+        ; fade black -> color then fade color -> white
+        random_rgb12()
+        ubyte r=0
+        ubyte g=0
+        ubyte b=0
+        ubyte different
+        bar_size = 0
+
+        repeat {
+            different = false
+            if r != cr {
+                different = true
+                r++
+            }
+            if g != cg {
+                different = true
+                g++
+            }
+            if b != cb {
+                different = true
+                b++
+            }
+            if not different
+                break
+            reds[bar_size] = r
+            greens[bar_size] = g
+            blues[bar_size] = b
+            bar_size++
+        }
+        repeat {
+            different = false
+            if r != 15 {
+                different = true
+                r++
+            }
+            if g != 15 {
+                different = true
+                g++
+            }
+            if b != 15 {
+                different = true
+                b++
+            }
+            if not different
+                break
+            reds[bar_size] = r
+            greens[bar_size] = g
+            blues[bar_size] = b
+            bar_size++
+        }
+        ; mirror bottom half from top half
+        ubyte mi = bar_size-1
+        repeat mi {
+            reds[bar_size] = reds[mi]
+            greens[bar_size] = greens[mi]
+            blues[bar_size] = blues[mi]
+            bar_size++
+            mi--
+        }
+        ; make rest of bar black (bars are not always the same length using the simplistic algorithm above...)
+        while bar_size != 48+16 {
+            reds[bar_size] = $0
+            greens[bar_size] = $0
+            blues[bar_size] = $0
+            bar_size++
+        }
+    }
+
+    sub set_palette() {
+        ubyte ix
+        for ix in 0 to 48+15 {
+            uword color = mkword(reds[ix], (greens[ix] << 4) | blues[ix] )
+            palette.set_color(ix, color)
+        }
+    }
+}