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%import c64lib
%import c64utils
%zeropage basicsafe
main {
const uword bitmap_address = $2000
sub start() {
; enable bitmap screen, erase it and set colors to black/white.
c64.SCROLY |= %00100000
c64.VMCSB = (c64.VMCSB & %11110000) | %00001000 ; $2000-$3fff
memset(bitmap_address, 320*200/8, 0)
c64scr.clear_screen($10, 0)
lines()
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circles()
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}
sub circles() {
ubyte xx
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for xx in 3 to 7 {
circle(xx*50-100, 10+xx*16, (xx+6)*4)
disc(xx*50-100, 10+xx*16, (xx+6)*2)
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}
}
sub lines() {
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ubyte ix
for ix in 1 to 15 {
line(10, 10, ix*4, 50) ; TODO fix lines of lenghts > 128
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}
}
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sub line(ubyte x1, ubyte y1, ubyte x2, ubyte y2) {
; Bresenham algorithm
byte d = 0
ubyte dx = abs(x2 - x1)
ubyte dy = abs(y2 - y1)
ubyte dx2 = 2 * dx
ubyte dy2 = 2 * dy
byte ix = sgn(x2 as byte - x1 as byte)
byte iy = sgn(y2 as byte - y1 as byte)
ubyte x = x1
ubyte y = y1
if dx >= dy {
forever {
plot(x, y)
if x==x2
return
x += ix
d += dy2
if d > dx {
y += iy
d -= dx2
}
}
} else {
forever {
plot(x, y)
if y == y2
return
y += iy
d += dx2
if d > dy {
x += ix
d -= dy2
}
}
}
}
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sub circle(uword xcenter, ubyte ycenter, ubyte radius) {
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; Midpoint algorithm
ubyte x = radius
ubyte y = 0
byte decisionOver2 = 1-x
while x>=y {
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plot(xcenter + x, ycenter + y as ubyte)
plot(xcenter - x, ycenter + y as ubyte)
plot(xcenter + x, ycenter - y as ubyte)
plot(xcenter - x, ycenter - y as ubyte)
plot(xcenter + y, ycenter + x as ubyte)
plot(xcenter - y, ycenter + x as ubyte)
plot(xcenter + y, ycenter - x as ubyte)
plot(xcenter - y, ycenter - x as ubyte)
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y++
if decisionOver2<=0
decisionOver2 += 2*y+1
else {
x--
decisionOver2 += 2*(y-x)+1
}
}
}
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sub disc(uword cx, ubyte cy, ubyte radius) {
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; Midpoint algorithm, filled
ubyte x = radius
ubyte y = 0
byte decisionOver2 = 1-x
uword xx
while x>=y {
for xx in cx to cx+x {
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plot(xx, cy + y as ubyte)
plot(xx, cy - y as ubyte)
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}
for xx in cx-x to cx-1 {
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plot(xx, cy + y as ubyte)
plot(xx, cy - y as ubyte)
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}
for xx in cx to cx+y {
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plot(xx, cy + x as ubyte)
plot(xx, cy - x as ubyte)
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}
for xx in cx-y to cx {
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plot(xx, cy + x as ubyte)
plot(xx, cy - x as ubyte)
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}
y++
if decisionOver2<=0
decisionOver2 += 2*y+1
else {
x--
decisionOver2 += 2*(y-x)+1
}
}
}
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sub plot(uword px, ubyte py) {
; TODO put this in a tuned asm plot routine
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; fast asm plot via lookup tables http://codebase64.org/doku.php?id=base:various_techniques_to_calculate_adresses_fast_common_screen_formats_for_pixel_graphics
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ubyte[] ormask = [128, 64, 32, 16, 8, 4, 2, 1]
uword addr = bitmap_address + 320*(py>>3) + (py & 7) + (px & %0000001111111000)
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@(addr) |= ormask[lsb(px) & 7]
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}
}