Class: GD::GIS::PointsLayer

Inherits:
Object
  • Object
show all
Defined in:
lib/gd/gis/layer_points.rb

Overview

Renders point data as icons (markers) with optional labels.

A PointsLayer draws markers for arbitrary data records. Longitude and latitude values are extracted using callables, allowing the layer to work with any data structure.

Optionally, text labels can be rendered next to each marker.

Instance Method Summary collapse

Constructor Details

#initialize(data, lon:, lat:, icon:, label: nil, font: nil, size: 12, color: [0, 0, 0], font_color: nil, symbol: 0) ⇒ PointsLayer

Creates a new points layer.

Parameters:

  • data (Enumerable) —

    collection of data records

  • lon (#call) —

    callable extracting longitude from a data record

  • lat (#call) —

    callable extracting latitude from a data record

  • icon (String, Array<GD::Color>, nil) —

    path to an icon image, or [fill, stroke] colors, or nil to generate a random marker

  • label (#call, nil) (defaults to: nil) —

    callable extracting label text from a data record

  • font (String, nil) (defaults to: nil) —

    font path used for labels

  • size (Integer) (defaults to: 12) —

    font size in pixels

  • color (Array<Integer>) (defaults to: [0, 0, 0]) —

    label color as RGB array



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# File 'lib/gd/gis/layer_points.rb', line 33

def initialize(
  data,
  lon:,
  lat:,
  icon:,
  label: nil,
  font: nil,
  size: 12,
  color: [0, 0, 0],
  font_color: nil,
  symbol: 0
)
  @data = data
  @lon = lon
  @lat = lat
  @color = color
  @font_color = font_color

  if icon.is_a?(Array) || icon.nil?
    fill, stroke = icon || [GD::GIS::ColorHelpers.random_rgb, GD::GIS::ColorHelpers.random_rgb]
    @icon = build_default_marker(fill, stroke)
  elsif %w[numeric alphabetic symbol].include?(icon)
    @icon = icon
  else
    @icon = GD::Image.open(icon)
    @icon.alpha_blending = true
    @icon.save_alpha = true
  end

  @label = label
  @font  = font
  @size  = size

  @r, @g, @b, @a = color
  @a = 0 if @a.nil?

  @symbol = symbol
end

Instance Method Details

#build_default_marker(fill, stroke) ⇒ GD::Image

Builds a default circular marker icon.

Parameters:

  • fill (GD::Color)
  • stroke (GD::Color)

Returns:

  • (GD::Image) 


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# File 'lib/gd/gis/layer_points.rb', line 77

def build_default_marker(fill, stroke)
  size = 32

  img = GD::Image.new(size, size)
  img.antialias = true

  cx = size / 2
  cy = size / 2
  r  = 5

  # stroke
  img.arc(cx, cy, (r * 2) + 4, (r * 2) + 4, 0, 360, stroke)

  # fill
  img.filled_arc(cx, cy, r * 2, r * 2, 0, 360, fill)

  img
end

#draw_symbol_circle!(img:, x:, y:, symbol:, bg_color:, font_color:, font:, font_size:, angle: 0.0) ⇒ Object

Draws a filled circle (bullet) with a centered numeric label.

  • x, y: circle center in pixels

  • y for text() is BASELINE (not top). We compute baseline to center the text.



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# File 'lib/gd/gis/layer_points.rb', line 162

def draw_symbol_circle!(img:, x:, y:, symbol:, bg_color:, font_color:, font:, font_size:, angle: 0.0)
  diameter = radius_from_text(img, symbol, font: font, size: font_size) * 2

  # 1) Bullet background
  img.filled_ellipse(x, y, diameter, diameter, bg_color)

  # 2) Measure text in pixels (matches rendering)
  text = symbol.to_s
  w, h = img.text_bbox(text, font: font, size: font_size, angle: angle)

  # 3) Compute centered position:
  # text() uses baseline Y, so:
  # top_y     = y - h/2
  # baseline  = top_y + h = y + h/2
  text_x = (x - (w / 2.0)).round
  text_y = (y + (h / 2.0)).round

  # 4) Draw number
  img.text(
    text,
    x: text_x,
    y: text_y,
    font: font,
    size: font_size,
    color: font_color
  )
end

#radius_from_text(img, text, font:, size:, padding: 4) ⇒ Object

Calculates a circle radius that fully contains the rendered text.

img : GD::Image text : String (number, letters, etc.) font : path to .ttf size : font size in points padding : extra pixels around text (visual breathing room)



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# File 'lib/gd/gis/layer_points.rb', line 198

def radius_from_text(img, text, font:, size:, padding: 4)
  w, h = img.text_bbox(
    text.to_s,
    font: font,
    size: size
  )

  # Use the larger dimension to ensure the text fits
  ([w, h].max / 2.0).ceil + padding
end

#render!(img, projector) ⇒ void

This method returns an undefined value.

Renders all points onto the image.

Parameters:

  • img (GD::Image) —

    target image

  • projector (#call) —

    callable converting (lon, lat) → (x, y)



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# File 'lib/gd/gis/layer_points.rb', line 103

def render!(img, projector)
  value =
    case @icon
    when "numeric", "symbol"
      @symbol
    when "alphabetic"
      (@symbol + 96).chr
    else
      @icon
    end

  if @icon.is_a?(GD::Image)
    w = @icon.width
    h = @icon.height
  else
    w = radius_from_text(img, value, font: @font, size: @size) * 2
  end

  @data.each do |row|
    lon = @lon.call(row)
    lat = @lat.call(row)

    x, y = projector.call(lon, lat)

    next unless @label && @font

    text = @label.call(row)
    next if text.nil? || text.strip.empty?

    font_h = @size * 1.1

    if @icon == "numeric" || @icon == "alphabetic" || @icon == "symbol"
      draw_symbol_circle!(
        img: img,
        x: x,
        y: y,
        symbol: value,
        bg_color: @color,
        font_color: @font_color,
        font: @font,
        font_size: @size
      )
    else
      img.copy(@icon, x - (w / 2), y - (h / 2), 0, 0, w, h)
    end

    img.text(text,
             x: x + (w / 2) + 4,
             y: y + (font_h / 2),
             size: @size,
             color: @font_color,
             font: @font)
  end
end