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Extract a helper.
This commit is contained in:
Kartik K. Agaram 2021-07-11 09:25:24 -07:00
parent 7e21abe0c9
commit 70a03be0d0
1 changed files with 39 additions and 33 deletions
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@ -486,39 +486,10 @@ fn _dither-pgm-unordered src: (addr array byte), width: int, height: int, buf: (
{
compare x, width
break-if->=
var error/ebx: int <- _read-dithering-error buf, x, y, width
# error += src_color << 16
var curr/eax: byte <- _read-pgm-buffer src, x, y, width
var curr-int/eax: int <- copy curr
#? draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, curr-int, 2/fg 0/bg
curr-int <- shift-left 0x10 # we have 32 bits; we'll use 16 bits for the fraction and leave 8 for unanticipated overflow
error <- add curr-int
# tmp = max(error, 0)
var tmp/eax: int <- copy error
{
compare tmp, 0
break-if->=
tmp <- copy 0
}
# round tmp to nearest multiple of 0x100000
{
var tmp2/ecx: int <- copy tmp
tmp2 <- and 0xfffff
compare tmp2, 0x80000
break-if-<
tmp <- add 0x80000
}
tmp <- and 0xf00000
# error -= tmp
error <- subtract tmp
# color = tmp >> 20 + 16
var color/eax: int <- copy tmp
color <- shift-right-signed 0x14
color <- add 0x10
#? draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, color, 3/fg 0/bg
#? draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, " ", 7/fg 0/bg
var color-byte/eax: byte <- copy-byte color
_write-raw-buffer dest, x, y, width, color-byte
var color/eax: byte <- _read-pgm-buffer src, x, y, width
var error/ebx: int <- copy 0
color, error <- compute-color-and-error buf, color, x, y, width
_write-raw-buffer dest, x, y, width, color
_diffuse-dithering-error-floyd-steinberg buf, x, y, width, height, error
x <- increment
loop
@ -529,6 +500,41 @@ fn _dither-pgm-unordered src: (addr array byte), width: int, height: int, buf: (
}
}
fn compute-color-and-error buf: (addr array int), initial-color: byte, x: int, y: int, width: int -> _/eax: byte, _/ebx: int {
var error/ebx: int <- _read-dithering-error buf, x, y, width
# error += initial-color << 16
var color-int/eax: int <- copy initial-color
#? draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, initial-color-int, 2/fg 0/bg
color-int <- shift-left 0x10 # we have 32 bits; we'll use 16 bits for the fraction and leave 8 for unanticipated overflow
error <- add color-int
# tmp = max(error, 0)
var tmp/eax: int <- copy error
{
compare tmp, 0
break-if->=
tmp <- copy 0
}
# round tmp to nearest multiple of 0x100000
{
var tmp2/ecx: int <- copy tmp
tmp2 <- and 0xfffff
compare tmp2, 0x80000
break-if-<
tmp <- add 0x80000
}
tmp <- and 0xf00000
# error -= tmp
error <- subtract tmp
# color = tmp >> 20 + 16
var color/eax: int <- copy tmp
color <- shift-right-signed 0x14
color <- add 0x10
#? draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, color, 3/fg 0/bg
#? draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, " ", 7/fg 0/bg
var color-byte/eax: byte <- copy-byte color
return color-byte, error
}
# Use Floyd-Steinberg algorithm for turning an image of greyscale pixels into
# one of pure black or white pixels.
#