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;;; Subroutine: render
;;; Convert 1px per byte array at pixarray to packed 8px/byte at screen.
; pixarray is 170x170. screen is 256x170.
; each screen line is: 43 blank px, 170 graphics px, 43 blank.
; This is slow. It takes around 40 jiffies (0.6 sec). However, it only
; happens once per generate. So not worth optimizing, really.
screenbyte = FR0
colcount = FR0+1
; RENDER_PROFILE = 1
render:
.ifdef RENDER_PROFILE
lda RTCLOK+1
sta $0600
lda RTCLOK+2
sta $0601
.endif
lda #<screen
sta screenptr
lda #>screen
sta screenptr+1
lda #<pixarray
sta pixptr
lda #>pixarray
sta pixptr+1
ldx #0
rline_loop:
lda #0
sta colcount
sta screenbyte
; clear whole line. this is why pixarray is offset from screen by
; one screen line.
ldy #$1f
rclr:
sta (screenptr),y
dey
bpl rclr
; first pixels start at column 40 (5 bytes in)...
lda #5
sta screenbyte
lda #$10 ; ...plus, mask starts out 0001000, 3 more columns to the right.
sta pixmask
rpix_loop:
ldy colcount ; ranges 0 to 169
lda (pixptr),y
beq notset ; 0 = not set, non-zero = set
; if we found a set pixel, set it in the bitmap
ldy screenbyte
lda (screenptr),y
ora pixmask
sta (screenptr),y
notset:
; pixmask >>= 1; if(pixmask == 0) { pixmask = 0x80; screenbyte++; }
lsr pixmask
bcc pmok
ror pixmask
inc screenbyte
pmok:
inc colcount
lda colcount
cmp #$aa
bne rpix_loop
; pixptr += 0xaa;
clc
adc pixptr
sta pixptr
lda pixptr+1
adc #0
sta pixptr+1
; screenptr += 0x20;
clc
lda screenptr
adc #$20
sta screenptr
lda screenptr+1
adc #0
sta screenptr+1
inx
cpx #$aa ; hit last line yet?
bne rline_loop ; if not, go render next line.
.ifdef RENDER_PROFILE
lda RTCLOK+1
sta $0602
lda RTCLOK+2
sta $0603
.endif
rts
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