Module: GDAL::RasterBand::ColoringExtensions

Included in:
GDAL::RasterBand
Defined in:
lib/gdal/extensions/raster_band/coloring_extensions.rb

Overview

RasterBand methods added for dealing with colorizing.

Instance Method Summary collapse

Instance Method Details

#colorize!(*colors) ⇒ Object

Sets the band to be a Palette band, then applies an RGB color table using the given colors. Colors are distributed evenly across the table based on the number of colors given. Note that this will overwrite any existing color table that may be set on this band.

Examples:

Colors as RGB values

# This will make the first 128 values black, and the last 128, red.
my_band.colorize!([[0, 0, 0], [255, 0, 0]])

Colors as Hex values

# Same as above...
my_band.colorize!(%w[#000000 #FF0000])


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# File 'lib/gdal/extensions/raster_band/coloring_extensions.rb', line 23

def colorize!(*colors)
  return if colors.empty?

  self.color_interpretation ||= :GCI_PaletteIndex
  table = GDAL::ColorTable.new(:GPI_RGB)
  table.add_color_entry(0, 0, 0, 0, 255)

  # Start at 1 instead of 0 because we manually set the first color entry
  # to white.
  color_entry_index_range =
    case data_type
    when :GDT_Byte then 1..255
    when :GDT_UInt16 then 1..65_535
    else raise "Can't colorize a #{data_type} band--must be :GDT_Byte or :GDT_UInt16"
    end

  bin_count = (color_entry_index_range.last + 1) / colors.size.to_f

  color_entry_index_range.step do |color_entry_index|
    color_number = (color_entry_index / bin_count).floor.to_i
    color = colors[color_number]

    # TODO: Fix possible uninitialized rgb_array
    rgb_array = hex_to_rgb(color) unless color.is_a?(Array)
    table.add_color_entry(color_entry_index,
                          rgb_array[0], rgb_array[1], rgb_array[2], 255)
  end

  self.color_table = table
end

#colors_as_hex ⇒ Array<String>

Gets the colors from the associated ColorTable and returns an Array of Strings, where the RGB color for each ColorEntry has been converted to Hex.



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# File 'lib/gdal/extensions/raster_band/coloring_extensions.rb', line 69

def colors_as_hex
  colors_as_rgb.map do |rgba|
    rgb = rgba.to_a[0..2]

    "##{rgb[0].to_s(16)}#{rgb[1].to_s(16)}#{rgb[2].to_s(16)}"
  end
end

#colors_as_rgb ⇒ Array<Array<Integer>>

Gets the colors from the associated ColorTable and returns an Array of those, where each ColorEntry is [R, G, B, A].



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# File 'lib/gdal/extensions/raster_band/coloring_extensions.rb', line 58

def colors_as_rgb
  return [] unless color_table

  color_table.color_entries_as_rgb.map(&:to_a)
end

#hex_to_rgb(hex) ⇒ Object 



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# File 'lib/gdal/extensions/raster_band/coloring_extensions.rb', line 78

def hex_to_rgb(hex)
  hex = hex.sub(/^#/, "")
  matches = hex.match(/(?<red>[a-zA-Z0-9]{2})(?<green>[a-zA-Z0-9]{2})(?<blue>[a-zA-Z0-9]{2})/)

  [matches[:red].to_i(16), matches[:green].to_i(16), matches[:blue].to_i(16)]
end