Tinkering with sixel in powershell

SixelTinkering.ps1

<#
  My rambling notes from trying to understand sixels and how to use them in Windows Terminal.
  
  I read up on a bunch of github issues, https://vt100.net/shuford/terminal/all_about_sixels.txt and wikipedia sixels pages

  Each vertically stacked "pixel" in a sixel has a value to the power of 2 starting with 1 and ending at 32.

  [*] 1 = 2^0
  [*] 2 = 2^1
  [*] 4 = 2^2
  [*] 8 = 2^3
  [*] 16 = 2^4
  [*] 32 = 2^5
    = 63 total

  For each vertical stack of pixels you add up all of the values of the pixels in that stack that are turned on.
  e.g for just the first pixel turned on you would get 1, for the first two pixels turned on you would get 3,
      for the first three pixels turned on you would get 7, etc.
  These total values are all unique (thanks Mathematics) and are used to send one value to the terminal to tell
  it how many pixels to light up.

  To make sixels easy to encode the unique values have an offset applied to so they can be represented in ASCII.
  The offset is 63, so the first unique value is 1 + 63 = 64, the second unique value is 3 + 63 = 66, etc.

  The table below shows some of the potential layouts and and the ASCII value that is sent to the terminal.
  ██ = pixel turned on
  -- = pixel turned off

     Value =  1   2   3   4   5   6   7 ...  56
  + Offset = 64  65  66  67  68  69  70     119
     ASCII =  @   A   B   C   D   E   F       w
Position 1 = ██  --  ██  --  ██  --  ██      --
Position 2 = --  ██  ██  --  --  ██  ██      --
Position 3 = --  --  --  ██  ██  ██  ██      --
Position 4 = --  --  --  --  --  --  --      ██
Position 5 = --  --  --  --  --  --  --      ██
Position 6 = --  --  --  --  --  --  --      ██

   Each sixel can only be one color so to draw a stack of six pixels with a mixture of colors you need to
   send multiple sixels to the terminal and write overtop of them. E.g. write an "@" in red to make the top
   pixel red and then write a "$" to send the print head back the the start of the line, then write an
   "A" in green to make the second pixel green.

   To make things confusing the width of the sixel doesn't correspond to the width or height of character
   cells in the terminal.

   Three rows of sixels in Windows Terminal is approximately the height of two lines of text.
   To render a square you require 12 sixels in a row.

   Because the terminal enters a special mode to render sixels you can't mix and match sixel rendering with
   normal escape codes or text rendering very easily.

   If you were to write a line of text, then send the console cursor back to the start of the line and enter
   sixel mode to render an image, then exit sixel mode, the text would be erased even if the sixel rendering
   is shorter than the original text.

   This makes it pretty difficult to embed sixels inside any other widgets like borders provided by libraries
   like Spectre.Console as far as I can tell.

   From my playing in at least the windows terminal case if the sixel is rendered first the text layer
   could be written overtop while leaving the sixel data intact but it's not guaranteed to work in all
   terminals and trying to accurately position the text vs sixel data would be difficult and error prone.

   So at the moment I can only really see it being used to dump image data to the terminal.

#>

$enterSixelMode = "`ePq"
$exitSixelMode = "`e\"
$carriageReturn = "$"
$lineFeed = "-"
$repeat = "!"
$createPalette = "#"
$choosePalette = "#"
$sixelOneToThreeOn = "F"
$sixelFourToSixOn = "w"
$allSixelsOn = "~"

# Draws two half height lines

$demoSixelLines = @(
   # Turn the sixel rendering mode on
   $enterSixelMode,
   # Add a color to the palette, color 0, mode is 2 (RGB), R=100%, G=0%, B=0%
   "${createPalette}0;2;100;0;0",
   # Add a color to the palette, color 1, mode is 2 (RGB), R=0%, G=100%, B=0%
   "${createPalette}1;2;0;100;0",
   # Add a color to the palette, color 2, mode is 2 (RGB), R=0%, G=0%, B=100%
   "${createPalette}2;2;0;0;100",
   # Draw the top half of the first line red height=3, width=18, then green height=3, width=18
   # Then send the print head back to the start of the line with the carriage return character
   "${choosePalette}0${repeat}18${sixelOneToThreeOn}${choosePalette}1${repeat}18${sixelOneToThreeOn}${carriageReturn}",
   # Draw the bottom half of the first line, green height=3, width=18, then blue height=3, width=18
   "${choosePalette}1${repeat}18${sixelFourToSixOn}${choosePalette}2${repeat}18${sixelFourToSixOn}${lineFeed}",
   # Draw the second second line, three squares, blue, red, green
   "${choosePalette}2${repeat}12${allSixelsOn}${choosePalette}0${repeat}12${allSixelsOn}${choosePalette}1${repeat}12${allSixelsOn}${lineFeed}",
   # Turn the sixel rendering mode off
   $exitSixelMode
)

$demoSixelLinesRaw = $demoSixelLines -join "`n"
$demoSixelLinesEscaped = $demoSixelLinesRaw -replace "`e", "``e"

# Example render
Write-Host -ForegroundColor Green "Sixel demo"
Write-Host "Sixel data:"
Write-Host -ForegroundColor DarkGray $demoSixelLinesEscaped
Write-Host "Sixel render:"
Write-Host $demoSixelLinesRaw

# Example of attempting to write sixel data on the same line as text
Write-Host -ForegroundColor Green "Sixel overwrite text"
Write-Host "Text that will attempt to be overwritten by sixel data in 3 secs`r" -NoNewline
Start-Sleep -Seconds 3
Write-Host $demoSixelLinesRaw
Write-Host "The text was overwritten by the sixel data across the whole line even though sixel data was shorter"

# Example of attempting to write text on top of sixel data
Write-Host -ForegroundColor Green "Text overwrite sixel"
Write-Host $demoSixelLinesRaw
Start-Sleep -Seconds 3
Write-Host "`e[2AText that will attempt to overwrite sixel data`n"
Write-Host "The text should have been written on top of the sixel data but the sixel data was only partially overwritten"

sixel.mp4