module GeoElevation

# File lib/images.rb, line 8
def self.elevation_image(width, height, latitude_interval, longitude_interval, max_elevation)
    #(latitude_interval and latitude_interval.length == 0) or raise "Invalid latitude_interval: #{latitude_interval}"
    srtm = GeoElevation::Srtm.new
    image = Image.new(width, height) { self.background_color='black' }
    for x in 0..height
        for y in 0..width
            latitude = latitude_interval[0] + (x / width.to_f) * (latitude_interval[1] - latitude_interval[0])
            longitude = longitude_interval[0] + (y / height.to_f) * (longitude_interval[1] - longitude_interval[0])
            elevation = srtm.get_elevation(latitude, longitude)

            #puts "(#{x}, #{y}) -> (#{latitude}, #{longitude}) #{elevation}, #{max_elevation}, #{elevation/max_elevation.to_f}"

            if elevation == nil
                pixel = Pixel.new(255*256, 255*256, 255*256)
            elsif elevation == 0
                pixel = Pixel.new(0*256, 0*256, 255*256)
            else
                elevation_ratio = elevation/max_elevation.to_f
                if elevation_ratio > 1.0
                    elevation_ratio = 1.0
                end
                pixel = Pixel.new(0*256, elevation_ratio*255*256, 0*256)
            end

            image.pixel_color(y, width - x, pixel)
        end
    end
    image
end

# File lib/images.rb, line 40
def self.world_undulation_image(width, height)
    egm = GeoElevation::Undulations.new
    min, max = 0, 0

    file_position = nil
    image = Image.new(width, height) { self.background_color='black' }
    (0..height).each do |w|
        (0..width).each do |h|
            latitude = -(w / height.to_f) * 180 + 90
            longitude = (h / width.to_f) * 360 - 180
            value = egm.get_undulation(latitude, longitude) / 2
            #puts "#{binary[0..7]} #{binary[8..15]} #{binary[16..23]} #{binary[24..31]}"
            #puts "#{w}, #{h} -> #{latitude}, #{longitude} -> #{value}"
            min = value > max ? value : max
            max = value < min ? value : min
            #puts "value=#{value}, min=#{min}, max=#{max}"
            value = (value * 1100).to_i
            pixel = Pixel.new(value, value, value)
            image.pixel_color(h, w, pixel)
        end
    end
    puts file_position

    image
end