prog8/examples/mandelbrot-gfx.p8

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%import c64graphics
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%import c64flt
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%zeropage floatsafe
; Draw a mandelbrot in graphics mode (the image will be 256 x 200 pixels).
; NOTE: this will take an eternity to draw on a real c64.
; even in Vice in warp mode (700% speed on my machine) it's slow, but you can see progress
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main {
const ubyte width = 255
const ubyte height = 200
const ubyte max_iter = 16
sub start() {
graphics.enable_bitmap_mode()
ubyte pixelx
ubyte pixely
for pixely in 0 to height-1 {
float yy = (pixely as float)/0.4/height - 1.0
for pixelx in 0 to width-1 {
float xx = (pixelx as float)/0.3/width - 2.2
float xsquared = 0.0
float ysquared = 0.0
float x = 0.0
float y = 0.0
ubyte iter = 0
while iter<max_iter and xsquared+ysquared<4.0 {
y = x*y*2.0 + yy
x = xsquared - ysquared + xx
xsquared = x*x
ysquared = y*y
iter++
}
if iter & 1
graphics.plot(pixelx, pixely)
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}
}
repeat {
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}
}
}