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fixed circle and disc geometry

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This commit is contained in:
Irmen de Jong 2020-12-30 00:06:01 +01:00
parent c3b82f2cfa
commit df6698c98f
1 changed files with 53 additions and 24 deletions
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77
compiler/res/prog8lib/c64/graphics.p8
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@ -31,6 +31,7 @@ graphics {
txt.fill_screen(pixelcolor << 4 | bgcolor, 0)
}
; TODO optimize if horizontal or vertical:
sub line(uword @zp x1, ubyte @zp y1, uword @zp x2, ubyte @zp y2) {
; Bresenham algorithm.
; This code special-cases various quadrant loops to allow simple ++ and -- operations.
@ -108,42 +109,71 @@ graphics {
}
}
sub fillrect(uword x, uword y, uword width, uword height) {
; TODO cx16.GRAPH_draw_rect(x, y, width, height, 0, 1)
}
sub rect(uword x, uword y, uword width, uword height) {
; TODO cx16.GRAPH_draw_rect(x, y, width, height, 0, 0)
}
sub horizontal_line(uword x, ubyte y, uword length) {
if not length
return
internal_plotx = x
repeat length {
internal_plot(y)
internal_plotx++
}
}
sub vertical_line(uword x, ubyte y, ubyte height) {
if not height
return
internal_plotx = x
repeat height {
internal_plot(y)
y++
}
}
sub circle(uword xcenter, ubyte ycenter, ubyte radius) {
; Midpoint algorithm
if radius==0
return
ubyte @zp ploty
ubyte @zp xx = radius
ubyte @zp yy = 0
byte @zp decisionOver2 = 1-xx as byte
word @zp decisionOver2 = (1 as word)-radius
while xx>=yy {
internal_plotx = xcenter + xx
while radius>=yy {
internal_plotx = xcenter + radius
ploty = ycenter + yy
internal_plot(ploty)
internal_plotx = xcenter - xx
internal_plotx = xcenter - radius
internal_plot(ploty)
internal_plotx = xcenter + xx
internal_plotx = xcenter + radius
ploty = ycenter - yy
internal_plot(ploty)
internal_plotx = xcenter - xx
internal_plotx = xcenter - radius
internal_plot(ploty)
internal_plotx = xcenter + yy
ploty = ycenter + xx
ploty = ycenter + radius
internal_plot(ploty)
internal_plotx = xcenter - yy
internal_plot(ploty)
internal_plotx = xcenter + yy
ploty = ycenter - xx
ploty = ycenter - radius
internal_plot(ploty)
internal_plotx = xcenter - yy
internal_plot(ploty)
yy++
if decisionOver2<=0
decisionOver2 += 2*yy+1
decisionOver2 += (yy as word)*2+1
else {
xx--
decisionOver2 += 2*(yy-xx)+1
radius--
decisionOver2 += (yy as word -radius)*2+1
}
}
}
@ -152,34 +182,33 @@ graphics {
; Midpoint algorithm, filled
if radius==0
return
ubyte @zp xx = radius
ubyte @zp yy = 0
byte decisionOver2 = 1-xx as byte
word decisionOver2 = (1 as word)-radius
while xx>=yy {
while radius>=yy {
ubyte ycenter_plus_yy = ycenter + yy
ubyte ycenter_min_yy = ycenter - yy
ubyte ycenter_plus_xx = ycenter + xx
ubyte ycenter_min_xx = ycenter - xx
ubyte ycenter_plus_radius = ycenter + radius
ubyte ycenter_min_radius = ycenter - radius
internal_plotx = xcenter-xx
repeat xx*2+1 {
internal_plotx = xcenter-radius
repeat radius*2+1 {
internal_plot(ycenter_plus_yy)
internal_plot(ycenter_min_yy)
internal_plotx++
}
internal_plotx = xcenter-yy
repeat yy*2+1 {
internal_plot(ycenter_plus_xx)
internal_plot(ycenter_min_xx)
internal_plot(ycenter_plus_radius)
internal_plot(ycenter_min_radius)
internal_plotx++
}
yy++
if decisionOver2<=0
decisionOver2 += 2*yy+1
decisionOver2 += (yy as word)*2+1
else {
xx--
decisionOver2 += 2*(yy-xx)+1
radius--
decisionOver2 += (yy as word -radius)*2+1
}
}
}