feat(elixir): implement proper AprilTag generation
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Schuwi
@@ -8,8 +8,9 @@ defmodule ComponentsElixir.AprilTag do
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import Ecto.Query
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alias ComponentsElixir.AprilTag.Tag36h11
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@tag36h11_count 587
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@apriltag_size 200
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@doc """
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Returns the total number of available AprilTags in the tag36h11 family.
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@@ -116,43 +117,11 @@ defmodule ComponentsElixir.AprilTag do
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@doc """
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Generates an SVG string for an AprilTag with the given ID.
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This creates a basic SVG representation of the AprilTag pattern
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with the ID displayed below it for human readability.
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Note: This is a simplified implementation. For production use,
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you'd want to use the actual AprilTag generation algorithm or
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pre-generated assets.
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This creates an actual AprilTag pattern using real tag36h11 data
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when available, or falls back to a placeholder pattern.
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"""
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def generate_apriltag_svg(apriltag_id, opts \\ []) do
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size = Keyword.get(opts, :size, @apriltag_size)
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margin = Keyword.get(opts, :margin, div(size, 10))
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# For now, create a placeholder square pattern
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# In a real implementation, you'd generate the actual AprilTag pattern
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square_size = size - (2 * margin)
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"""
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<svg width="#{size}" height="#{size + 30}" xmlns="http://www.w3.org/2000/svg">
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<!-- White background -->
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<rect width="#{size}" height="#{size + 30}" fill="white"/>
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<!-- AprilTag placeholder (simplified) -->
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<rect x="#{margin}" y="#{margin}" width="#{square_size}" height="#{square_size}"
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fill="white" stroke="black" stroke-width="2"/>
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<!-- Simplified tag pattern - in reality this would be the actual AprilTag -->
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<rect x="#{margin + 10}" y="#{margin + 10}" width="#{square_size - 20}" height="#{square_size - 20}"
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fill="black"/>
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<rect x="#{margin + 20}" y="#{margin + 20}" width="#{square_size - 40}" height="#{square_size - 40}"
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fill="white"/>
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<!-- ID text below -->
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<text x="#{size / 2}" y="#{size + 20}" text-anchor="middle"
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font-family="Arial" font-size="14" font-weight="bold">
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ID: #{String.pad_leading(to_string(apriltag_id), 3, "0")}
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</text>
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</svg>
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"""
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Tag36h11.generate_apriltag_svg(apriltag_id, opts)
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end
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@doc """
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243
lib/components_elixir/apriltag/tag36h11.ex
Normal file
243
lib/components_elixir/apriltag/tag36h11.ex
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@@ -0,0 +1,243 @@
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defmodule ComponentsElixir.AprilTag.Tag36h11 do
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@moduledoc """
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Tag36h11 AprilTag family data and generation.
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Contains the actual bit patterns for all 587 tags in the tag36h11 family,
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sourced from the AprilRobotics apriltag-imgs repository.
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"""
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import Bitwise
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# PostScript file path containing all tag36h11 patterns
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@patterns_file "apriltags.ps"
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# Parse a PostScript line like: (april.tag.Tag36h11, id = 42) <hexpattern> maketag
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defp parse_ps_line(line) do
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case Regex.run(~r/\(april\.tag\.Tag36h11, id = (\d+)\) <([0-9a-fA-F]+)> maketag/, line) do
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[_, id_str, hex_pattern] ->
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{String.to_integer(id_str), String.downcase(hex_pattern)}
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_ ->
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nil
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end
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end
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# Extract patterns from PostScript file at compile time
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@all_patterns (
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path = Path.join([File.cwd!(), "apriltags.ps"])
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if File.exists?(path) do
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File.read!(path)
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|> String.split("\n")
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|> Enum.filter(&String.contains?(&1, "april.tag.Tag36h11"))
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|> Enum.map(fn line ->
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case Regex.run(~r/\(april\.tag\.Tag36h11, id = (\d+)\) <([0-9a-fA-F]+)> maketag/, line) do
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[_, id_str, hex_pattern] ->
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{String.to_integer(id_str), String.downcase(hex_pattern)}
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_ ->
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nil
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end
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end)
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|> Enum.reject(&is_nil/1)
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|> Map.new()
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else
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raise "Error: apriltags.ps file not found in project root. This file is required for AprilTag pattern generation."
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end
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)
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# Sample of real tag36h11 hex patterns from AprilRobotics repository
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# This will be populated with patterns extracted from the PostScript file
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@tag36h11_patterns @all_patterns
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@doc """
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Extracts all tag36h11 hex patterns from the PostScript file.
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Returns a map of {id => hex_pattern} for all 587 tags.
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"""
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def extract_patterns_from_ps_file(file_path \\ nil) do
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path = file_path || Path.join([File.cwd!(), @patterns_file])
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if File.exists?(path) do
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File.read!(path)
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|> String.split("\n")
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|> Enum.filter(&String.contains?(&1, "april.tag.Tag36h11"))
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|> Enum.map(&parse_ps_line/1)
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|> Enum.reject(&is_nil/1)
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|> Map.new()
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else
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%{} # Return empty map if file not found, will fall back to hardcoded patterns
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end
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end
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@doc """
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Gets the hex pattern for a given AprilTag ID.
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Returns nil if the ID is not available in our pattern data.
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"""
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def get_hex_pattern(id) when is_integer(id) and id >= 0 and id < 587 do
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Map.get(@tag36h11_patterns, id)
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end
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def get_hex_pattern(_), do: nil
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@doc """
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Converts a PostScript hex pattern to a 10x10 binary matrix using 2-bits-per-pixel
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with proper row padding handling.
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PostScript pads each scanline to byte boundary: 10 pixels × 2 bits = 20 bits,
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rounded up to 24 bits = 3 bytes per row. The last 2 pixels per row are padding.
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Returns a list of lists where true = black pixel, false = white pixel.
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"""
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def hex_to_binary_matrix_2bpp(hex_string) when is_binary(hex_string) do
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clean_hex =
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hex_string
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|> String.replace(~r/[<>\s]/, "")
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|> String.upcase()
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bytes = Base.decode16!(clean_hex, case: :mixed)
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# Each scanline is padded to a byte boundary: 3 bytes per 10 pixels (2 bpp)
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row_bytes = 3
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rows =
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for row <- 0..9 do
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<<_::binary-size(row * row_bytes), r::binary-size(row_bytes), _::binary>> = bytes
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<<b0, b1, b2>> = r
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samples =
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[
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b0 >>> 6 &&& 0x3, b0 >>> 4 &&& 0x3, b0 >>> 2 &&& 0x3, b0 &&& 0x3,
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b1 >>> 6 &&& 0x3, b1 >>> 4 &&& 0x3, b1 >>> 2 &&& 0x3, b1 &&& 0x3,
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b2 >>> 6 &&& 0x3, b2 >>> 4 &&& 0x3, b2 >>> 2 &&& 0x3, b2 &&& 0x3
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]
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|> Enum.take(10) # drop the 2 padding samples at end of row
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|> Enum.map(&(&1 == 0)) # 0 = black, 3 = white → boolean
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samples
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end
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rows
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end
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@doc """
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Legacy method - kept for backward compatibility.
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Use hex_to_binary_matrix_2bpp/1 for correct AprilTag parsing.
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"""
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def hex_to_binary_matrix(hex_string) when is_binary(hex_string) do
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hex_to_binary_matrix_2bpp(hex_string)
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end
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@doc """
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Generates an SVG string from a binary matrix.
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Takes a 10x10 binary matrix and converts it to an SVG representation
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using integer coordinates with viewBox scaling to eliminate seams.
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Only black modules are drawn over a white background.
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"""
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def binary_matrix_to_svg(binary_matrix, opts \\ []) do
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size = Keyword.get(opts, :size, 200) # final CSS size in px
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id_text = Keyword.get(opts, :id_text, "")
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# binary_matrix is 10x10 of booleans: true=black, false=white
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modules_w = 10
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modules_h = 10
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# Build rects only for black modules, aligned to integer coords in the viewBox space
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black_cells =
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binary_matrix
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|> Enum.with_index()
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|> Enum.flat_map(fn {row, y} ->
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row
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|> Enum.with_index()
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|> Enum.filter(fn {is_black, _x} -> is_black end)
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|> Enum.map(fn {_is_black, x} ->
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~s(<rect x="#{x}" y="#{y}" width="1" height="1" />)
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end)
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end)
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|> Enum.join()
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"""
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<?xml version="1.0" encoding="UTF-8"?>
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<svg xmlns="http://www.w3.org/2000/svg"
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width="#{size}" height="#{size + 24}"
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viewBox="0 0 #{modules_w} #{modules_h + 2}"
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shape-rendering="crispEdges">
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<!-- white background (includes 2 units below for caption area) -->
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<rect x="0" y="0" width="#{modules_w}" height="#{modules_h + 2}" fill="white"/>
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<!-- tag area outline (optional) -->
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<rect x="0" y="0" width="#{modules_w}" height="#{modules_h}" fill="white" stroke="black" stroke-width="0"/>
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<!-- black modules -->
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<g fill="black">
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#{black_cells}
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</g>
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<!-- caption -->
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#{if id_text != "" do
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~s(<text x="#{modules_w/2}" y="#{modules_h + 1.4}" text-anchor="middle"
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font-family="Arial" font-size="0.9">#{id_text}</text>)
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else "" end}
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</svg>
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"""
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end
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@doc """
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Generates a complete AprilTag SVG for a given ID.
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This is the main function that combines hex pattern lookup,
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binary conversion, and SVG generation.
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"""
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def generate_apriltag_svg(id, opts \\ []) do
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case get_hex_pattern(id) do
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nil ->
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# Fallback to placeholder for IDs we don't have patterns for yet
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generate_placeholder_svg(id, opts)
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hex_pattern ->
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binary_matrix = hex_to_binary_matrix_2bpp(hex_pattern)
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id_text = "ID: #{String.pad_leading(to_string(id), 3, "0")}"
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opts_with_id = Keyword.put(opts, :id_text, id_text)
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binary_matrix_to_svg(binary_matrix, opts_with_id)
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end
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end # Generate a placeholder pattern for IDs we don't have real data for yet
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defp generate_placeholder_svg(id, opts) do
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size = Keyword.get(opts, :size, 200)
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margin = Keyword.get(opts, :margin, div(size, 10))
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square_size = size - (2 * margin)
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"""
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<svg width="#{size}" height="#{size + 30}" xmlns="http://www.w3.org/2000/svg">
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<!-- White background -->
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<rect width="#{size}" height="#{size + 30}" fill="white"/>
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<!-- AprilTag placeholder (simplified) -->
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<rect x="#{margin}" y="#{margin}" width="#{square_size}" height="#{square_size}"
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fill="white" stroke="black" stroke-width="2"/>
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<!-- Simplified tag pattern - placeholder for missing real pattern -->
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<rect x="#{margin + 10}" y="#{margin + 10}" width="#{square_size - 20}" height="#{square_size - 20}"
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fill="black"/>
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<rect x="#{margin + 20}" y="#{margin + 20}" width="#{square_size - 40}" height="#{square_size - 40}"
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fill="white"/>
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<!-- ID text below -->
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<text x="#{size / 2}" y="#{size + 20}" text-anchor="middle"
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font-family="Arial" font-size="14" font-weight="bold">
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ID: #{String.pad_leading(to_string(id), 3, "0")} (Placeholder)
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</text>
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</svg>
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"""
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end
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@doc """
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Returns the list of AprilTag IDs that have real pattern data available.
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"""
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def available_patterns do
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Map.keys(@tag36h11_patterns) |> Enum.sort()
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end
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@doc """
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Returns whether a real pattern is available for the given ID.
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"""
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def has_real_pattern?(id) do
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Map.has_key?(@tag36h11_patterns, id)
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end
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end
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