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dither 256-level greyscale to 8-level greyscale

This commit is contained in:
Kartik K. Agaram 2021-07-11 03:10:53 -07:00
parent eb6cee6022
commit 430dd67cb2
2 changed files with 212 additions and 2 deletions
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55
88.pgm Normal file
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@ -0,0 +1,55 @@
P2
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159
img.mu
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@ -109,8 +109,8 @@ fn render-image screen: (addr screen), _img: (addr image), xmin: int, ymin: int,
break-if-!=
var img2-storage: image
var img2/edi: (addr image) <- address img2-storage
dither-pgm-unordered-monochrome img, img2
render-pbm-image screen, img2, xmin, ymin, width, height
dither-pgm-unordered img, img2
render-raw-image screen, img2, xmin, ymin, width, height
return
}
{
@ -433,6 +433,94 @@ fn _dither-pgm-unordered-monochrome src: (addr array byte), width: int, height:
}
}
fn dither-pgm-unordered _src: (addr image), _dest: (addr image) {
var src/esi: (addr image) <- copy _src
var dest/edi: (addr image) <- copy _dest
# copy 'width'
var src-width-a/ecx: (addr int) <- get src, width
var src-width/ecx: int <- copy *src-width-a
{
var dest-width-a/edx: (addr int) <- get dest, width
copy-to *dest-width-a, src-width
}
# copy 'height'
var src-height-a/edx: (addr int) <- get src, height
var src-height/edx: int <- copy *src-height-a
{
var dest-height-a/ecx: (addr int) <- get dest, height
copy-to *dest-height-a, src-height
}
# transform 'data'
var capacity/ebx: int <- copy src-width
capacity <- multiply src-height
var dest/edi: (addr image) <- copy _dest
var dest-data-ah/eax: (addr handle array byte) <- get dest, data
populate dest-data-ah, capacity
var _dest-data/eax: (addr array byte) <- lookup *dest-data-ah
var dest-data/edi: (addr array byte) <- copy _dest-data
# needs a buffer to temporarily hold more than 256 levels of precision
var buffer-storage: (array int 0xc0000)
var buffer/ebx: (addr array int) <- address buffer-storage
var src-data-ah/eax: (addr handle array byte) <- get src, data
var _src-data/eax: (addr array byte) <- lookup *src-data-ah
var src-data/esi: (addr array byte) <- copy _src-data
_dither-pgm-unordered src-data, src-width, src-height, buffer, dest-data
}
fn _dither-pgm-unordered src: (addr array byte), width: int, height: int, buf: (addr array int), dest: (addr array byte) {
var y/edx: int <- copy 0
{
compare y, height
break-if->=
var x/ecx: int <- copy 0
{
compare x, width
break-if->=
var error/ebx: int <- _read-pgm-buffer buf, x, y, width
$_dither-pgm-unordered-monochrome:update-error: {
# error += src_color << 16
var curr/eax: byte <- _read-pgm-byte-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-pgm-byte-buffer dest, x, y, width, color-byte
}
_diffuse-dithering-error-floyd-steinberg buf, x, y, width, height, error
x <- increment
loop
}
move-cursor-to-left-margin-of-next-line 0/screen
y <- increment
loop
}
}
# Use Floyd-Steinberg algorithm for turning an image of greyscale pixels into
# one of pure black or white pixels.
#
@ -754,3 +842,70 @@ fn render-ppm-image screen: (addr screen), _img: (addr image), xmin: int, ymin:
loop
}
}
fn render-raw-image screen: (addr screen), _img: (addr image), xmin: int, ymin: int, width: int, height: int {
var img/esi: (addr image) <- copy _img
# yratio = height/img->height
var img-height-a/eax: (addr int) <- get img, height
var img-height/xmm0: float <- convert *img-height-a
var yratio/xmm1: float <- convert height
yratio <- divide img-height
# xratio = width/img->width
var img-width-a/eax: (addr int) <- get img, width
var img-width/ebx: int <- copy *img-width-a
var img-width-f/xmm0: float <- convert img-width
var xratio/xmm2: float <- convert width
xratio <- divide img-width-f
# esi = img->data
var img-data-ah/eax: (addr handle array byte) <- get img, data
var _img-data/eax: (addr array byte) <- lookup *img-data-ah
var img-data/esi: (addr array byte) <- copy _img-data
var len/edi: int <- length img-data
#
var one/eax: int <- copy 1
var one-f/xmm3: float <- convert one
var width-f/xmm4: float <- convert width
var height-f/xmm5: float <- convert height
var zero/eax: int <- copy 0
var zero-f/xmm0: float <- convert zero
var y/xmm6: float <- copy zero-f
{
compare y, height-f
break-if-float>=
var imgy-f/xmm5: float <- copy y
imgy-f <- divide yratio
var imgy/edx: int <- truncate imgy-f
var x/xmm7: float <- copy zero-f
{
compare x, width-f
break-if-float>=
var imgx-f/xmm5: float <- copy x
imgx-f <- divide xratio
var imgx/ecx: int <- truncate imgx-f
var idx/eax: int <- copy imgy
idx <- multiply img-width
idx <- add imgx
# error info in case we rounded wrong and 'index' will fail bounds-check
compare idx, len
{
break-if-<
set-cursor-position 0/screen, 0x20/x 0x20/y
draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, imgx, 3/fg 0/bg
draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, imgy, 4/fg 0/bg
draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, idx, 5/fg 0/bg
}
var color-a/eax: (addr byte) <- index img-data, idx
var color/eax: byte <- copy-byte *color-a
var color-int/eax: int <- copy color
var screenx/ecx: int <- convert x
screenx <- add xmin
var screeny/edx: int <- convert y
screeny <- add ymin
pixel screen, screenx, screeny, color-int
x <- add one-f
loop
}
y <- add one-f
loop
}
}