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optimized iff planar to chunky

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This commit is contained in:
Irmen de Jong 2020-12-23 19:48:44 +01:00
parent 7d08380c7f
commit 48a4c46a6c
1 changed files with 53 additions and 11 deletions
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64
examples/cx16/imageviewer/iff_module.p8
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@ -119,14 +119,14 @@ iff_module {
}
}
uword bitplane_stride
ubyte bitplane_stride
uword interleave_stride
uword offsetx
uword offsety
sub start_plot() {
bitplane_stride = width>>3
interleave_stride = bitplane_stride * num_planes
bitplane_stride = lsb(width>>3)
interleave_stride = (bitplane_stride as uword) * num_planes
offsetx = 0
offsety = 0
if width < graphics.WIDTH
@ -190,17 +190,59 @@ iff_module {
}
sub planar_to_chunky_scanline() {
; ubyte[8] masks = [128,64,32,16,8,4,2,1]
uword x
for x in 0 to width-1 {
ubyte bitnr = ((lsb(x) ^ 255) & 7) + 1
; ubyte mask = masks[lsb(x) & 7]
uword pixptr = x/8 + scanline_data_ptr
ubyte bits=0
repeat num_planes {
ubyte bb = @(pixptr) >> bitnr ; extract bit
ror(bits) ; shift it into the byte
pixptr += bitplane_stride
}
bits >>= 8-num_planes
ubyte bits = 0
%asm {{
bra +
_masks .byte 128, 64, 32, 16, 8, 4, 2, 1
+ lda x
and #7
tay
lda _masks,y
sta P8ZP_SCRATCH_B1 ; mask
phx
ldx num_planes
ldy #0
- lda (pixptr),y
clc
and P8ZP_SCRATCH_B1
beq +
sec
+ ror bits ; shift planar bit into chunky byte
lda pixptr
; clc
adc bitplane_stride
sta pixptr
bcc +
inc pixptr+1
+ dex
bne -
plx
lda #8
sec
sbc num_planes
beq +
tay
- lsr bits
dey
bne -
+
}}
; the assembly above is the optimized version of this:
; repeat num_planes {
; clear_carry()
; if @(pixptr) & mask
; set_carry()
; ror(bits) ; shift planar bit into chunky byte
; pixptr += bitplane_stride
; }
; bits >>= 8-num_planes
cx16.FB_set_pixel(bits)
}
}