ASCII dithering
In this example, we are going to approximate a grayscale gradient with an ASCII ramp such as .:-=+*#%@.
using Images
using DitherPunk
using TestImages
img = testimage("cameraman")
When loading an image, we need to compensate for the aspect ratio of ASCII characters.
img = imresize(img; ratio=(1//14, 1//6))
We then define an ASCII ramp and a corresponding grayscale color scheme of matching length.
ascii_ramp = split(" .:-=+*#%@", "")
cs = Gray.(range(0, 1; length=10))![](data:image/svg+xml;utf-8,<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"
width="180mm" height="25mm"
viewBox="0 0 10 1" preserveAspectRatio="none"
shape-rendering="crispEdges" stroke="none">
<rect width=".94" height=".96" x="0" y="0" fill="%23000000" />
<rect width=".94" height=".96" x="1" y="0" fill="%231C1C1C" />
<rect width=".94" height=".96" x="2" y="0" fill="%23393939" />
<rect width=".94" height=".96" x="3" y="0" fill="%23555555" />
<rect width=".94" height=".96" x="4" y="0" fill="%23717171" />
<rect width=".94" height=".96" x="5" y="0" fill="%238E8E8E" />
<rect width=".94" height=".96" x="6" y="0" fill="%23AAAAAA" />
<rect width=".94" height=".96" x="7" y="0" fill="%23C6C6C6" />
<rect width=".94" height=".96" x="8" y="0" fill="%23E3E3E3" />
<rect width=".94" height=".96" x="9" y="0" fill="%23FFFFFF" />
</svg>)
Dithering will return an IndirectArray:
d = dither(img, cs)
Instead of showing d as an image, we can use its indices to select the corresponding ASCII characters from the ramp.
mat = ascii_ramp[d.index]37×86 Matrix{SubString{String}}:
"+" "*" "*" "+" "*" "*" "*" "*" … "*" "+" "*" "+" "*" "+" "+"
"*" "+" "+" "*" "*" "+" "*" "+" "+" "*" "+" "+" "+" "*" "*"
"+" "*" "*" "+" "+" "*" "+" "*" "*" "+" "*" "*" "+" "+" "+"
"*" "+" "+" "*" "*" "*" "*" "+" "+" "*" "+" "+" "*" "*" "+"
"+" "*" "*" "+" "*" "+" "*" "*" "*" "+" "*" "*" "+" "+" "*"
"*" "+" "+" "*" "+" "*" "*" "+" … "+" "+" "+" "+" "*" "+" "+"
"+" "*" "*" "*" "*" "*" "+" "*" "*" "+" "*" "+" "+" "+" "+"
"*" "+" "*" "+" "*" "*" "*" "*" "+" "+" "+" "+" "+" "*" "+"
"*" "*" "*" "*" "*" "*" "*" "*" "+" "+" "*" "+" "*" "+" "+"
"*" "+" "*" "*" "*" "*" "*" "*" "+" "+" "+" "+" "+" "+" "+"
⋮ ⋮ ⋱ ⋮ ⋮
"=" "+" "+" "=" "+" "+" "+" "+" "=" "=" "-" "-" "=" "=" "="
"+" "+" "+" "+" "+" "+" "+" "=" "=" "=" "-" "=" "=" "=" "="
"+" "=" "+" "+" "+" "+" "+" "+" … "=" "=" "=" "+" "=" "+" "+"
"=" "=" "+" "=" "+" "+" "=" "+" "+" "=" "+" "=" "=" "=" "="
"+" "=" "+" "+" "+" "=" "=" "+" "=" "=" "=" "=" "=" "=" "-"
"=" "=" "=" "+" "=" "-" "+" "=" "=" "+" "=" "=" "+" "=" "="
"+" "+" "*" "+" "=" "+" "+" "=" "=" "-" "=" "=" "=" "=" "-"
"=" "=" "=" "+" "=" "=" "=" "-" … "=" "-" "-" "=" "=" "=" "+"
"=" "=" "=" "=" "+" "=" "+" "=" "=" "=" "-" "=" "=" "-" "="Pretty printing each row of this matrix will output the image:
for r in eachrow(mat)
println(join(r))
end+**+*********************#**#*#*#*#*#**#*#*#*#***#**#************************++*+*+*++
*++**+*+*+*************************#*##*#*#*#*##**#**#*#***#*********+**+*++**++*+++**
+**++*+******+*********#**#*##*#*#**#**#*#*#****#************************+**+***+**+++
*++****++*+*********************#*##*##*#*#*####*####*#*#**********+*+*+***+*+++*++**+
+**+*+******+**********#**#*#*#*****#*##*#*#**#*#****#*****#*************++*****+**++*
*++*+**+**********#**#*****#*#*####*: :=*##*##*#*#*#**#**#*************+***++++++++*++
+*****+***************#*#*#***#*** . =:#*#*#*#*#*#*************+**+*+***+*+*++++
*+*+**********#*#*#*#**#*#*###*#* . . .. .:*#****#*****#***********+**+*+++*+++++*+
*******************#*##*#*****## *. ##==..::-##***#************+***+*++*+*+++*+*++
*+************#*#*#****##*##**- . ..==++***#.:-**%.=@%**#***********+***+**+++++++++++
**+*+************#**#-. .. . #==: :=+-:*:-::.::+.#************+**++**++**+*+*++*++
*************#*#**#: . .. . .. . -+=. .+*+::.:=:.++*+++**************++**++*++++++++
+***************-. . . .. . : .=. . .-**+.::.: .*************+*+*+**++*++*+*+*+++
**+*+********#.. .. . . . . ... * ..+=+##%%#::**********+*+*******+**+*+++++++++
+******+*+**. . . . . ... . . + #*#%%+ .****+*+***+****+*++*+*++*+*+*+*++++
*++*++***** .. . .. . . . . + .... .+ . . :********+***++*****+*+**+++++++++++
*******+****. . ... . . - . . . .+.#=: . ***+*+*+**+***=+*+**+*++*+*++*+++++
+*+*+*+**+****= . . .. :::.. . ... - . .. #*********+*+*+#***+**+**+*+*+++++*+
***+*******+***: .. .. . .....:. . . : =# *+ .***+*+*********##**++**+*+++*++*+++
*+****+*+****** . . :. .. :** .- +#**** .******+*+*+++#***+**+*#*#**+++++++
***+*******+**. . .. . .. ... .. ..***.:.+=%*+*== .***#**********#**+***+*+*++*+*+*+
=====++*****# . .. . . . .. . *### +*++#*+==++ .#+**####+++#***+*++++++*+*++++++
---+=++*+==* . . . . .. ... .. %###...#*+#**##*+* .****++++++=++*+*******+==+=++==
:-::-::::-:. . .. .. . .. :*+++ +-=-+%=+**+*+= .*.:*-#-..-+#*#*#*##*+=-::----
=+++=+++++. . ... . .. .... .:++++. +-=.:**-+=-:-= .*::-=:.:..:...-*+::.===..:..:
=+*++==++. . . .. .. .. -=+== =-==-+%--+===+=+= .++==+=+=+++++++++++==+++=++=
+++=+=++- . .... .. .. . .. -*++* :*=++=#+++++-*+++= ++=+=+=+==+=+=====+========
++=+=+== . . . . . .. .-==++= =.==++=#+======-*=== .===+=============-======-=
=++=++++++. .. ... . .. .. +++++ =-++++-#+++++++++=%++ ++=+============+===--===
+++++++=+=++ : ... . . .. +++*+= +.+=+++=++++++===++==*=:#++++++==+===+======-====
+=++++++++++. :. .. . ..+++++ *++=+==+=++=++++++==+++- .====--======+==+===+=++
==+=++=+++*+...::: . . . . +++==- - -===++=++=++++++++++++++ ++=++==+======++=+====
+=+++==+=++:...:::::. . .::-+===+. *=-==+===+===++=+++=+++=+=+ .++======+==+========-
===+=-+==-+... :::.+ : :..::+=++++:@@++===++++++==+=+=+++++*+++=-*=+==++-=======+==+==
++*+=++=+=*..:: :.=+:......=+=+=+:=@=+=+=+===+====+++++==+====-==-*+=+=-+-=+=--=-====-
===+===-=+= ..:::.=+:--::-..===+=.##=======++===+++++=++==+++=-===-*+=+====-====--===+
====+=+=+=+.:. ::=-=- .-:: -=+-=:=@=+=+++++==+=====+=+-==+=+-+++==+-#=-=+-=-=====-==-=This page was generated using Literate.jl.