forgot to `git add` a file

1 files changed, 1098 insertions, 0 deletions

diff --git a/511image.mu b/511image.mu
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+# Loading images from disk, rendering images to screen.
+#
+# Currently supports ASCII Netpbm formats.
+#   https://en.wikipedia.org/wiki/Netpbm#File_formats
+
+type image {
+  type: int  # supported types:
+             #  1: portable bitmap (P1) - pixels 0 or 1
+             #  2: portable greymap (P2) - pixels 1-byte greyscale values
+             #  3: portable pixmap (P3) - pixels 3-byte rgb values
+  max: int
+  width: int
+  height: int
+  data: (handle array byte)
+}
+
+fn initialize-image _self: (addr image), in: (addr stream byte) {
+  var self/esi: (addr image) <- copy _self
+  var mode-storage: slice
+  var mode/ecx: (addr slice) <- address mode-storage
+  next-word in, mode
+  {
+    var P1?/eax: boolean <- slice-equal? mode, "P1"
+    compare P1?, 0/false
+    break-if-=
+    var type-a/eax: (addr int) <- get self, type
+    copy-to *type-a, 1/ppm
+    initialize-image-from-pbm self, in
+    return
+  }
+  {
+    var P2?/eax: boolean <- slice-equal? mode, "P2"
+    compare P2?, 0/false
+    break-if-=
+    var type-a/eax: (addr int) <- get self, type
+    copy-to *type-a, 2/pgm
+    initialize-image-from-pgm self, in
+    return
+  }
+  {
+    var P3?/eax: boolean <- slice-equal? mode, "P3"
+    compare P3?, 0/false
+    break-if-=
+    var type-a/eax: (addr int) <- get self, type
+    copy-to *type-a, 3/ppm
+    initialize-image-from-ppm self, in
+    return
+  }
+  abort "initialize-image: unrecognized image type"
+}
+
+# dispatch to a few variants with mostly identical boilerplate
+fn render-image screen: (addr screen), _img: (addr image), xmin: int, ymin: int, width: int, height: int {
+  var img/esi: (addr image) <- copy _img
+  var type-a/eax: (addr int) <- get img, type
+  {
+    compare *type-a, 1/pbm
+    break-if-!=
+    render-pbm-image screen, img, xmin, ymin, width, height
+    return
+  }
+  {
+    compare *type-a, 2/pgm
+    break-if-!=
+    var img2-storage: image
+    var img2/edi: (addr image) <- address img2-storage
+    dither-pgm-unordered img, img2
+    render-raw-image screen, img2, xmin, ymin, width, height
+    return
+  }
+  {
+    compare *type-a, 3/ppm
+    break-if-!=
+    var img2-storage: image
+    var img2/edi: (addr image) <- address img2-storage
+    dither-ppm-unordered img, img2
+    render-raw-image screen, img2, xmin, ymin, width, height
+    return
+  }
+  abort "render-image: unrecognized image type"
+}
+
+## helpers
+
+# import a black-and-white ascii bitmap (each pixel is 0 or 1)
+fn initialize-image-from-pbm _self: (addr image), in: (addr stream byte) {
+  var self/esi: (addr image) <- copy _self
+  var curr-word-storage: slice
+  var curr-word/ecx: (addr slice) <- address curr-word-storage
+  # load width, height
+  next-word in, curr-word
+  var tmp/eax: int <- parse-decimal-int-from-slice curr-word
+  var width/edx: int <- copy tmp
+  next-word in, curr-word
+  tmp <- parse-decimal-int-from-slice curr-word
+  var height/ebx: int <- copy tmp
+  # save width, height
+  var dest/eax: (addr int) <- get self, width
+  copy-to *dest, width
+  dest <- get self, height
+  copy-to *dest, height
+  # initialize data
+  var capacity/edx: int <- copy width
+  capacity <- multiply height
+  var data-ah/edi: (addr handle array byte) <- get self, data
+  populate data-ah, capacity
+  var _data/eax: (addr array byte) <- lookup *data-ah
+  var data/edi: (addr array byte) <- copy _data
+  var i/ebx: int <- copy 0
+  {
+    compare i, capacity
+    break-if->=
+    next-word in, curr-word
+    var src/eax: int <- parse-decimal-int-from-slice curr-word
+    {
+      var dest/ecx: (addr byte) <- index data, i
+      copy-byte-to *dest, src
+    }
+    i <- increment
+    loop
+  }
+}
+
+# render a black-and-white ascii bitmap (each pixel is 0 or 1)
+fn render-pbm-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 src-a/eax: (addr byte) <- index img-data, idx
+      var src/eax: byte <- copy-byte *src-a
+      var color-int/eax: int <- copy src
+      {
+        compare color-int, 0/black
+        break-if-=
+        color-int <- copy 0xf/white
+      }
+      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
+  }
+}
+
+# import a greyscale ascii "greymap" (each pixel is a shade of grey from 0 to 255)
+fn initialize-image-from-pgm _self: (addr image), in: (addr stream byte) {
+  var self/esi: (addr image) <- copy _self
+  var curr-word-storage: slice
+  var curr-word/ecx: (addr slice) <- address curr-word-storage
+  # load width, height
+  next-word in, curr-word
+  var tmp/eax: int <- parse-decimal-int-from-slice curr-word
+  var width/edx: int <- copy tmp
+  next-word in, curr-word
+  tmp <- parse-decimal-int-from-slice curr-word
+  var height/ebx: int <- copy tmp
+  # check and save color levels
+  next-word in, curr-word
+  {
+    tmp <- parse-decimal-int-from-slice curr-word
+    compare tmp, 0xff
+    break-if-=
+    draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, "levels of grey is not 255; continuing and hoping for the best", 0x2b/fg 0/bg
+  }
+  var dest/edi: (addr int) <- get self, max
+  copy-to *dest, tmp
+  # save width, height
+  dest <- get self, width
+  copy-to *dest, width
+  dest <- get self, height
+  copy-to *dest, height
+  # initialize data
+  var capacity/edx: int <- copy width
+  capacity <- multiply height
+  var data-ah/edi: (addr handle array byte) <- get self, data
+  populate data-ah, capacity
+  var _data/eax: (addr array byte) <- lookup *data-ah
+  var data/edi: (addr array byte) <- copy _data
+  var i/ebx: int <- copy 0
+  {
+    compare i, capacity
+    break-if->=
+    next-word in, curr-word
+    var src/eax: int <- parse-decimal-int-from-slice curr-word
+    {
+      var dest/ecx: (addr byte) <- index data, i
+      copy-byte-to *dest, src
+    }
+    i <- increment
+    loop
+  }
+}
+
+# render a greyscale ascii "greymap" (each pixel is a shade of grey from 0 to 255) by quantizing the shades
+fn render-pgm-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 src-a/eax: (addr byte) <- index img-data, idx
+      var src/eax: byte <- copy-byte *src-a
+      var color-int/eax: int <- nearest-grey src
+      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
+  }
+}
+
+fn nearest-grey level-255: byte -> _/eax: int {
+  var result/eax: int <- copy level-255
+  result <- shift-right 4
+  result <- add 0x10
+  return result
+}
+
+fn dither-pgm-unordered-monochrome _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/eax: (addr int) <- get src, width
+  var tmp/eax: int <- copy *src-width-a
+  var src-width: int
+  copy-to src-width, tmp
+  {
+    var dest-width-a/edx: (addr int) <- get dest, width
+    copy-to *dest-width-a, tmp
+  }
+  # copy 'height'
+  var src-height-a/eax: (addr int) <- get src, height
+  var tmp/eax: int <- copy *src-height-a
+  var src-height: int
+  copy-to src-height, tmp
+  {
+    var dest-height-a/ecx: (addr int) <- get dest, height
+    copy-to *dest-height-a, tmp
+  }
+  # 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 errors-storage: (array int 0xc0000)
+  var errors/ebx: (addr array int) <- address errors-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
+  var y/edx: int <- copy 0
+  {
+    compare y, src-height
+    break-if->=
+    var x/ecx: int <- copy 0
+    {
+      compare x, src-width
+      break-if->=
+      var curr/eax: byte <- _read-pgm-buffer src-data, x, y, src-width
+      var curr-int/eax: int <- copy curr
+      curr-int <- shift-left 0x10  # we have 32 bits; we'll use 16 bits for the fraction and leave 8 for unanticipated overflow
+      var error/esi: int <- _read-dithering-error errors, x, y, src-width
+      error <- add curr-int
+      $_dither-pgm-unordered-monochrome:update-error: {
+        compare error, 0x800000
+        {
+          break-if->=
+          _write-raw-buffer dest-data, x, y, src-width, 0/black
+          break $_dither-pgm-unordered-monochrome:update-error
+        }
+        _write-raw-buffer dest-data, x, y, src-width, 1/white
+        error <- subtract 0xff0000
+      }
+      _diffuse-dithering-error-floyd-steinberg errors, x, y, src-width, src-height, error
+      x <- increment
+      loop
+    }
+    move-cursor-to-left-margin-of-next-line 0/screen
+    y <- increment
+    loop
+  }
+}
+
+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/eax: (addr int) <- get src, width
+  var tmp/eax: int <- copy *src-width-a
+  var src-width: int
+  copy-to src-width, tmp
+  {
+    var dest-width-a/edx: (addr int) <- get dest, width
+    copy-to *dest-width-a, tmp
+  }
+  # copy 'height'
+  var src-height-a/eax: (addr int) <- get src, height
+  var tmp/eax: int <- copy *src-height-a
+  var src-height: int
+  copy-to src-height, tmp
+  {
+    var dest-height-a/ecx: (addr int) <- get dest, height
+    copy-to *dest-height-a, tmp
+  }
+  # compute scaling factor 255/max
+  var target-scale/eax: int <- copy 0xff
+  var scale-f/xmm7: float <- convert target-scale
+  var src-max-a/eax: (addr int) <- get src, max
+  var tmp-f/xmm0: float <- convert *src-max-a
+  scale-f <- divide tmp-f
+  # 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 errors-storage: (array int 0xc0000)
+  var errors/ebx: (addr array int) <- address errors-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
+  var y/edx: int <- copy 0
+  {
+    compare y, src-height
+    break-if->=
+    var x/ecx: int <- copy 0
+    {
+      compare x, src-width
+      break-if->=
+      var initial-color/eax: byte <- _read-pgm-buffer src-data, x, y, src-width
+      # . scale to 255 levels
+      var initial-color-int/eax: int <- copy initial-color
+      var initial-color-f/xmm0: float <- convert initial-color-int
+      initial-color-f <- multiply scale-f
+      initial-color-int <- convert initial-color-f
+      var error/esi: int <- _read-dithering-error errors, x, y, src-width
+      # error += (initial-color << 16)
+      {
+        var tmp/eax: int <- copy initial-color-int
+        tmp <- shift-left 0x10  # we have 32 bits; we'll use 16 bits for the fraction and leave 8 for unanticipated overflow
+        error <- add tmp
+      }
+      # nearest-color = nearest(error >> 16)
+      var nearest-color/eax: int <- copy error
+      nearest-color <- shift-right-signed 0x10
+      {
+        compare nearest-color, 0
+        break-if->=
+        nearest-color <- copy 0
+      }
+      {
+        compare nearest-color, 0xf0
+        break-if-<=
+        nearest-color <- copy 0xf0
+      }
+      # . truncate last 4 bits
+      nearest-color <- and 0xf0
+      # error -= (nearest-color << 16)
+      {
+        var tmp/eax: int <- copy nearest-color
+        tmp <- shift-left 0x10
+        error <- subtract tmp
+      }
+      # color-index = (nearest-color >> 4 + 16)
+      var color-index/eax: int <- copy nearest-color
+      color-index <- shift-right 4
+      color-index <- add 0x10
+      var color-index-byte/eax: byte <- copy-byte color-index
+      _write-raw-buffer dest-data, x, y, src-width, color-index-byte
+      _diffuse-dithering-error-floyd-steinberg errors, x, y, src-width, src-height, error
+      x <- increment
+      loop
+    }
+    y <- increment
+    loop
+  }
+}
+
+# Use Floyd-Steinberg algorithm for diffusing error at x, y in a 2D grid of
+# dimensions (width, height)
+#
+# https://tannerhelland.com/2012/12/28/dithering-eleven-algorithms-source-code.html
+#
+# Error is currently a fixed-point number with 16-bit fraction. But
+# interestingly this function doesn't care about that.
+fn _diffuse-dithering-error-floyd-steinberg errors: (addr array int), x: int, y: int, width: int, height: int, error: int {
+  {
+    compare error, 0
+    break-if-!=
+    return
+  }
+  var width-1/esi: int <- copy width
+  width-1 <- decrement
+  var height-1/edi: int <- copy height
+  height-1 <- decrement
+  # delta = error/16
+#?   show-errors errors, width, height, x, y
+  var delta/ecx: int <- copy error
+  delta <- shift-right-signed 4
+  # In Floyd-Steinberg, each pixel X transmits its errors to surrounding
+  # pixels in the following proportion:
+  #           X     7/16
+  #     3/16  5/16  1/16
+  var x/edx: int <- copy x
+  {
+    compare x, width-1
+    break-if->=
+    var tmp/eax: int <- copy 7
+    tmp <- multiply delta
+    var xright/edx: int <- copy x
+    xright <- increment
+    _accumulate-dithering-error errors, xright, y, width, tmp
+  }
+  var y/ebx: int <- copy y
+  {
+    compare y, height-1
+    break-if-<
+    return
+  }
+  var ybelow: int
+  copy-to ybelow, y
+  increment ybelow
+  {
+    compare x, 0
+    break-if-<=
+    var tmp/eax: int <- copy 3
+    tmp <- multiply delta
+    var xleft/edx: int <- copy x
+    xleft <- decrement
+    _accumulate-dithering-error errors, xleft, ybelow, width, tmp
+  }
+  {
+    var tmp/eax: int <- copy 5
+    tmp <- multiply delta
+    _accumulate-dithering-error errors, x, ybelow, width, tmp
+  }
+  {
+    compare x, width-1
+    break-if->=
+    var xright/edx: int <- copy x
+    xright <- increment
+    _accumulate-dithering-error errors, xright, ybelow, width, delta
+  }
+#?   show-errors errors, width, height, x, y
+}
+
+fn _accumulate-dithering-error errors: (addr array int), x: int, y: int, width: int, error: int {
+  var curr/esi: int <- _read-dithering-error errors, x, y, width
+  curr <- add error
+  _write-dithering-error errors, x, y, width, curr
+}
+
+fn _read-dithering-error _errors: (addr array int), x: int, y: int, width: int -> _/esi: int {
+  var errors/esi: (addr array int) <- copy _errors
+  var idx/ecx: int <- copy y
+  idx <- multiply width
+  idx <- add x
+  var result-a/eax: (addr int) <- index errors, idx
+  return *result-a
+}
+
+fn _write-dithering-error _errors: (addr array int), x: int, y: int, width: int, val: int {
+  var errors/esi: (addr array int) <- copy _errors
+  var idx/ecx: int <- copy y
+  idx <- multiply width
+  idx <- add x
+#?   draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, idx, 7/fg 0/bg
+#?   move-cursor-to-left-margin-of-next-line 0/screen
+  var src/eax: int <- copy val
+  var dest-a/edi: (addr int) <- index errors, idx
+  copy-to *dest-a, src
+}
+
+fn _read-pgm-buffer _buf: (addr array byte), x: int, y: int, width: int -> _/eax: byte {
+  var buf/esi: (addr array byte) <- copy _buf
+  var idx/ecx: int <- copy y
+  idx <- multiply width
+  idx <- add x
+  var result-a/eax: (addr byte) <- index buf, idx
+  var result/eax: byte <- copy-byte *result-a
+  return result
+}
+
+fn _write-raw-buffer _buf: (addr array byte), x: int, y: int, width: int, val: byte {
+  var buf/esi: (addr array byte) <- copy _buf
+  var idx/ecx: int <- copy y
+  idx <- multiply width
+  idx <- add x
+  var src/eax: byte <- copy val
+  var dest-a/edi: (addr byte) <- index buf, idx
+  copy-byte-to *dest-a, src
+}
+
+# some debugging helpers
+fn show-errors errors: (addr array int), width: int, height: int, x: int, y: int {
+  compare y, 1
+  {
+    break-if-=
+    return
+  }
+  compare x, 0
+  {
+    break-if-=
+    return
+  }
+  var y/edx: int <- copy 0
+  {
+    compare y, height
+    break-if->=
+    var x/ecx: int <- copy 0
+    {
+      compare x, width
+      break-if->=
+      var error/esi: int <- _read-dithering-error errors, x, y, width
+      psd "e", error, 5/fg, x, y
+      x <- increment
+      loop
+    }
+    move-cursor-to-left-margin-of-next-line 0/screen
+    y <- increment
+    loop
+  }
+}
+
+fn psd s: (addr array byte), d: int, fg: int, x: int, y: int {
+  {
+    compare y, 0x18
+    break-if->=
+    return
+  }
+  {
+    compare y, 0x1c
+    break-if-<=
+    return
+  }
+  {
+    compare x, 0x40
+    break-if->=
+    return
+  }
+#?   {
+#?     compare x, 0x48
+#?     break-if-<=
+#?     return
+#?   }
+  draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, s, 7/fg 0/bg
+  draw-int32-decimal-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, d, fg 0/bg
+}
+
+fn psx s: (addr array byte), d: int, fg: int, x: int, y: int {
+#?   {
+#?     compare y, 0x60
+#?     break-if->=
+#?     return
+#?   }
+#?   {
+#?     compare y, 0x6c
+#?     break-if-<=
+#?     return
+#?   }
+  {
+    compare x, 0x20
+    break-if->=
+    return
+  }
+#?   {
+#?     compare x, 0x6c
+#?     break-if-<=
+#?     return
+#?   }
+  draw-text-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, s, 7/fg 0/bg
+  draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen 0/screen, d, fg 0/bg
+}
+
+# import a color ascii "pixmap" (each pixel consists of 3 shades of r/g/b from 0 to 255)
+fn initialize-image-from-ppm _self: (addr image), in: (addr stream byte) {
+  var self/esi: (addr image) <- copy _self
+  var curr-word-storage: slice
+  var curr-word/ecx: (addr slice) <- address curr-word-storage
+  # load width, height
+  next-word in, curr-word
+  var tmp/eax: int <- parse-decimal-int-from-slice curr-word
+  var width/edx: int <- copy tmp
+  next-word in, curr-word
+  tmp <- parse-decimal-int-from-slice curr-word
+  var height/ebx: int <- copy tmp
+  next-word in, curr-word
+  # check color levels
+  {
+    tmp <- parse-decimal-int-from-slice curr-word
+    compare tmp, 0xff
+    break-if-=
+    abort "initialize-image-from-ppm: supports exactly 255 levels per rgb channel"
+  }
+  var dest/edi: (addr int) <- get self, max
+  copy-to *dest, tmp
+  # save width, height
+  dest <- get self, width
+  copy-to *dest, width
+  dest <- get self, height
+  copy-to *dest, height
+  # initialize data
+  var capacity/edx: int <- copy width
+  capacity <- multiply height
+  # . multiply by 3 for the r/g/b channels
+  var tmp/eax: int <- copy capacity
+  tmp <- shift-left 1
+  capacity <- add tmp
+  #
+  var data-ah/edi: (addr handle array byte) <- get self, data
+  populate data-ah, capacity
+  var _data/eax: (addr array byte) <- lookup *data-ah
+  var data/edi: (addr array byte) <- copy _data
+  var i/ebx: int <- copy 0
+  {
+    compare i, capacity
+    break-if->=
+    next-word in, curr-word
+    var src/eax: int <- parse-decimal-int-from-slice curr-word
+    {
+      var dest/ecx: (addr byte) <- index data, i
+      copy-byte-to *dest, src
+    }
+    i <- increment
+    loop
+  }
+}
+
+# import a color ascii "pixmap" (each pixel consists of 3 shades of r/g/b from 0 to 255)
+fn render-ppm-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
+      # . multiply by 3 for the r/g/b channels
+      {
+        var tmp/ecx: int <- copy idx
+        tmp <- shift-left 1
+        idx <- add tmp
+      }
+      # 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
+      }
+      # r channel
+      var r: int
+      {
+        var src-a/eax: (addr byte) <- index img-data, idx
+        var src/eax: byte <- copy-byte *src-a
+        copy-to r, src
+      }
+      idx <- increment
+      # g channel
+      var g: int
+      {
+        var src-a/eax: (addr byte) <- index img-data, idx
+        var src/eax: byte <- copy-byte *src-a
+        copy-to g, src
+      }
+      idx <- increment
+      # b channel
+      var b: int
+      {
+        var src-a/eax: (addr byte) <- index img-data, idx
+        var src/eax: byte <- copy-byte *src-a
+        copy-to b, src
+      }
+      idx <- increment
+      # plot nearest color
+      var color/eax: int <- nearest-color-euclidean r, g, b
+      var screenx/ecx: int <- convert x
+      screenx <- add xmin
+      var screeny/edx: int <- convert y
+      screeny <- add ymin
+      pixel screen, screenx, screeny, color
+      x <- add one-f
+      loop
+    }
+    y <- add one-f
+    loop
+  }
+}
+
+fn dither-ppm-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/eax: (addr int) <- get src, width
+  var tmp/eax: int <- copy *src-width-a
+  var src-width: int
+  copy-to src-width, tmp
+  {
+    var dest-width-a/edx: (addr int) <- get dest, width
+    copy-to *dest-width-a, tmp
+  }
+  # copy 'height'
+  var src-height-a/eax: (addr int) <- get src, height
+  var tmp/eax: int <- copy *src-height-a
+  var src-height: int
+  copy-to src-height, tmp
+  {
+    var dest-height-a/ecx: (addr int) <- get dest, height
+    copy-to *dest-height-a, tmp
+  }
+  # compute scaling factor 255/max
+  var target-scale/eax: int <- copy 0xff
+  var scale-f/xmm7: float <- convert target-scale
+  var src-max-a/eax: (addr int) <- get src, max
+  var tmp-f/xmm0: float <- convert *src-max-a
+  scale-f <- divide tmp-f
+  # allocate '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
+  # error buffers per r/g/b channel
+  var red-errors-storage: (array int 0xc0000)
+  var tmp/eax: (addr array int) <- address red-errors-storage
+  var red-errors: (addr array int)
+  copy-to red-errors, tmp
+  var green-errors-storage: (array int 0xc0000)
+  var tmp/eax: (addr array int) <- address green-errors-storage
+  var green-errors: (addr array int)
+  copy-to green-errors, tmp
+  var blue-errors-storage: (array int 0xc0000)
+  var tmp/eax: (addr array int) <- address blue-errors-storage
+  var blue-errors: (addr array int)
+  copy-to blue-errors, tmp
+  # transform 'data'
+  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
+  var y/edx: int <- copy 0
+  {
+    compare y, src-height
+    break-if->=
+    var x/ecx: int <- copy 0
+    {
+      compare x, src-width
+      break-if->=
+      # - update errors and compute color levels for current pixel in each channel
+      # update red-error with current image pixel
+      var red-error: int
+      {
+        var tmp/esi: int <- _read-dithering-error red-errors, x, y, src-width
+        copy-to red-error, tmp
+      }
+      {
+        var tmp/eax: int <- _ppm-error src-data, x, y, src-width, 0/red, scale-f
+        add-to red-error, tmp
+      }
+      # recompute red channel for current pixel
+      var red-level: int
+      {
+        var tmp/eax: int <- _error-to-ppm-channel red-error
+        copy-to red-level, tmp
+      }
+      # update green-error with current image pixel
+      var green-error: int
+      {
+        var tmp/esi: int <- _read-dithering-error green-errors, x, y, src-width
+        copy-to green-error, tmp
+      }
+      {
+        var tmp/eax: int <- _ppm-error src-data, x, y, src-width, 1/green, scale-f
+        add-to green-error, tmp
+      }
+      # recompute green channel for current pixel
+      var green-level: int
+      {
+        var tmp/eax: int <- _error-to-ppm-channel green-error
+        copy-to green-level, tmp
+      }
+      # update blue-error with current image pixel
+      var blue-error: int
+      {
+        var tmp/esi: int <- _read-dithering-error blue-errors, x, y, src-width
+        copy-to blue-error, tmp
+      }
+      {
+        var tmp/eax: int <- _ppm-error src-data, x, y, src-width, 2/blue, scale-f
+        add-to blue-error, tmp
+      }
+      # recompute blue channel for current pixel
+      var blue-level: int
+      {
+        var tmp/eax: int <- _error-to-ppm-channel blue-error
+        copy-to blue-level, tmp
+      }
+      # - figure out the nearest color
+      var nearest-color-index/eax: int <- nearest-color-euclidean red-level, green-level, blue-level
+      {
+        var nearest-color-index-byte/eax: byte <- copy-byte nearest-color-index
+        _write-raw-buffer dest-data, x, y, src-width, nearest-color-index-byte
+      }
+      # - diffuse errors
+      var red-level: int
+      var green-level: int
+      var blue-level: int
+      {
+        var tmp-red-level/ecx: int <- copy 0
+        var tmp-green-level/edx: int <- copy 0
+        var tmp-blue-level/ebx: int <- copy 0
+        tmp-red-level, tmp-green-level, tmp-blue-level <- color-rgb nearest-color-index
+        copy-to red-level, tmp-red-level
+        copy-to green-level, tmp-green-level
+        copy-to blue-level, tmp-blue-level
+      }
+      # update red-error
+      var red-level-error/eax: int <- copy red-level
+      red-level-error <- shift-left 0x10
+      subtract-from red-error, red-level-error
+      _diffuse-dithering-error-floyd-steinberg red-errors, x, y, src-width, src-height, red-error
+      # update green-error
+      var green-level-error/eax: int <- copy green-level
+      green-level-error <- shift-left 0x10
+      subtract-from green-error, green-level-error
+      _diffuse-dithering-error-floyd-steinberg green-errors, x, y, src-width, src-height, green-error
+      # update blue-error
+      var blue-level-error/eax: int <- copy blue-level
+      blue-level-error <- shift-left 0x10
+      subtract-from blue-error, blue-level-error
+      _diffuse-dithering-error-floyd-steinberg blue-errors, x, y, src-width, src-height, blue-error
+      #
+      x <- increment
+      loop
+    }
+    y <- increment
+    loop
+  }
+}
+
+# convert a single channel for a single image pixel to error space
+fn _ppm-error buf: (addr array byte), x: int, y: int, width: int, channel: int, _scale-f: float -> _/eax: int {
+  # current image pixel
+  var initial-level/eax: byte <- _read-ppm-buffer buf, x, y, width, channel
+  # scale to 255 levels
+  var initial-level-int/eax: int <- copy initial-level
+  var initial-level-f/xmm0: float <- convert initial-level-int
+  var scale-f/xmm1: float <- copy _scale-f
+  initial-level-f <- multiply scale-f
+  initial-level-int <- convert initial-level-f
+  # switch to fixed-point with 16 bits of precision
+  initial-level-int <- shift-left 0x10
+  return initial-level-int
+}
+
+fn _error-to-ppm-channel error: int -> _/eax: int {
+  # clamp(error >> 16)
+  var result/esi: int <- copy error
+  result <- shift-right-signed 0x10
+  {
+    compare result, 0
+    break-if->=
+    result <- copy 0
+  }
+  {
+    compare result, 0xff
+    break-if-<=
+    result <- copy 0xff
+  }
+  return result
+}
+
+# read from a buffer containing alternating bytes from r/g/b channels
+fn _read-ppm-buffer _buf: (addr array byte), x: int, y: int, width: int, channel: int -> _/eax: byte {
+  var buf/esi: (addr array byte) <- copy _buf
+  var idx/ecx: int <- copy y
+  idx <- multiply width
+  idx <- add x
+  var byte-idx/edx: int <- copy 3
+  byte-idx <- multiply idx
+  byte-idx <- add channel
+  var result-a/eax: (addr byte) <- index buf, byte-idx
+  var result/eax: byte <- copy-byte *result-a
+  return result
+}
+
+# each byte in the image data is a color of the current palette
+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
+  }
+}