%import c64textio ; bitmap pixel graphics module for the C64 ; only black/white monchrome for now ; assumes bitmap screen memory is $2000-$3fff graphics { const uword bitmap_address = $2000 sub enable_bitmap_mode() { ; enable bitmap screen, erase it and set colors to black/white. c64.SCROLY |= %00100000 c64.VMCSB = (c64.VMCSB & %11110000) | %00001000 ; $2000-$3fff clear_screen(1, 0) } sub clear_screen(ubyte pixelcolor, ubyte bgcolor) { memset(bitmap_address, 320*200/8, 0) txt.clear_screen(pixelcolor << 4 | bgcolor, 0) } 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. ; TODO rewrite this in optimized assembly if y1>y2 { ; make sure dy is always positive to avoid 8 instead of just 4 special cases swap(x1, x2) swap(y1, y2) } word @zp d = 0 ubyte positive_ix = true word @zp dx = x2 - x1 as word word @zp dy = y2 as word - y1 as word if dx < 0 { dx = -dx positive_ix = false } dx *= 2 dy *= 2 plotx = x1 if dx >= dy { if positive_ix { repeat { plot(y1) if plotx==x2 return plotx++ d += dy if d > dx { y1++ d -= dx } } } else { repeat { plot(y1) if plotx==x2 return plotx-- d += dy if d > dx { y1++ d -= dx } } } } else { if positive_ix { repeat { plot(y1) if y1 == y2 return y1++ d += dx if d > dy { plotx++ d -= dy } } } else { repeat { plot(y1) if y1 == y2 return y1++ d += dx if d > dy { plotx-- d -= dy } } } } } sub circle(uword xcenter, ubyte ycenter, ubyte radius) { ; Midpoint algorithm ubyte @zp ploty ubyte @zp xx = radius ubyte @zp yy = 0 byte @zp decisionOver2 = 1-xx as byte while xx>=yy { plotx = xcenter + xx ploty = ycenter + yy plot(ploty) plotx = xcenter - xx plot(ploty) plotx = xcenter + xx ploty = ycenter - yy plot(ploty) plotx = xcenter - xx plot(ploty) plotx = xcenter + yy ploty = ycenter + xx plot(ploty) plotx = xcenter - yy plot(ploty) plotx = xcenter + yy ploty = ycenter - xx plot(ploty) plotx = xcenter - yy plot(ploty) yy++ if decisionOver2<=0 decisionOver2 += 2*yy+1 else { xx-- decisionOver2 += 2*(yy-xx)+1 } } } sub disc(uword cx, ubyte cy, ubyte radius) { ; Midpoint algorithm, filled ubyte xx = radius ubyte yy = 0 byte decisionOver2 = 1-xx as byte while xx>=yy { ubyte cy_plus_yy = cy + yy ubyte cy_min_yy = cy - yy ubyte cy_plus_xx = cy + xx ubyte cy_min_xx = cy - xx for plotx in cx to cx+xx { plot(cy_plus_yy) plot(cy_min_yy) } for plotx in cx-xx to cx-1 { plot(cy_plus_yy) plot(cy_min_yy) } for plotx in cx to cx+yy { plot(cy_plus_xx) plot(cy_min_xx) } for plotx in cx-yy to cx { plot(cy_plus_xx) plot(cy_min_xx) } yy++ if decisionOver2<=0 decisionOver2 += 2*yy+1 else { xx-- decisionOver2 += 2*(yy-xx)+1 } } } ; here is the non-asm code for the plot routine below: ; sub plot_nonasm(uword px, ubyte py) { ; ubyte[] ormask = [128, 64, 32, 16, 8, 4, 2, 1] ; uword addr = bitmap_address + 320*(py>>3) + (py & 7) + (px & %0000000111111000) ; @(addr) |= ormask[lsb(px) & 7] ; } uword plotx ; 0..319 ; separate 'parameter' for plot() asmsub plot(ubyte ploty @A) { ; plotx is 16 bits 0 to 319... doesn't fit in a register %asm {{ tay stx P8ZP_SCRATCH_REG_X lda plotx+1 sta P8ZP_SCRATCH_W2+1 lsr a ; 0 sta P8ZP_SCRATCH_W2 lda plotx pha and #7 tax lda _y_lookup_lo,y clc adc P8ZP_SCRATCH_W2 sta P8ZP_SCRATCH_W2 lda _y_lookup_hi,y adc P8ZP_SCRATCH_W2+1 sta P8ZP_SCRATCH_W2+1 pla ; plotx and #%11111000 tay lda (P8ZP_SCRATCH_W2),y ora _ormask,x sta (P8ZP_SCRATCH_W2),y ldx P8ZP_SCRATCH_REG_X rts _ormask .byte 128, 64, 32, 16, 8, 4, 2, 1 ; note: this can be even faster if we also have a 256 byte x-lookup table, but hey. ; see http://codebase64.org/doku.php?id=base:various_techniques_to_calculate_adresses_fast_common_screen_formats_for_pixel_graphics ; the y lookup tables encodes this formula: bitmap_address + 320*(py>>3) + (py & 7) (y from 0..199) ; TODO can we use an assembly function for this to calc this? _y_lookup_hi .byte $20, $20, $20, $20, $20, $20, $20, $20, $21, $21, $21, $21, $21, $21, $21, $21 .byte $22, $22, $22, $22, $22, $22, $22, $22, $23, $23, $23, $23, $23, $23, $23, $23 .byte $25, $25, $25, $25, $25, $25, $25, $25, $26, $26, $26, $26, $26, $26, $26, $26 .byte $27, $27, $27, $27, $27, $27, $27, $27, $28, $28, $28, $28, $28, $28, $28, $28 .byte $2a, $2a, $2a, $2a, $2a, $2a, $2a, $2a, $2b, $2b, $2b, $2b, $2b, $2b, $2b, $2b .byte $2c, $2c, $2c, $2c, $2c, $2c, $2c, $2c, $2d, $2d, $2d, $2d, $2d, $2d, $2d, $2d .byte $2f, $2f, $2f, $2f, $2f, $2f, $2f, $2f, $30, $30, $30, $30, $30, $30, $30, $30 .byte $31, $31, $31, $31, $31, $31, $31, $31, $32, $32, $32, $32, $32, $32, $32, $32 .byte $34, $34, $34, $34, $34, $34, $34, $34, $35, $35, $35, $35, $35, $35, $35, $35 .byte $36, $36, $36, $36, $36, $36, $36, $36, $37, $37, $37, $37, $37, $37, $37, $37 .byte $39, $39, $39, $39, $39, $39, $39, $39, $3a, $3a, $3a, $3a, $3a, $3a, $3a, $3a .byte $3b, $3b, $3b, $3b, $3b, $3b, $3b, $3b, $3c, $3c, $3c, $3c, $3c, $3c, $3c, $3c .byte $3e, $3e, $3e, $3e, $3e, $3e, $3e, $3e _y_lookup_lo .byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47 .byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7 .byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47 .byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7 .byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47 .byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7 .byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47 .byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7 .byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47 .byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7 .byte $00, $01, $02, $03, $04, $05, $06, $07, $40, $41, $42, $43, $44, $45, $46, $47 .byte $80, $81, $82, $83, $84, $85, $86, $87, $c0, $c1, $c2, $c3, $c4, $c5, $c6, $c7 .byte $00, $01, $02, $03, $04, $05, $06, $07 }} } }