class CALIBRATION
-- This class is able to
-- - build some calibration grid with user assistance,
-- - save calibration grid,
-- - reload calibration grid,
-- - use calibration grid for coordinates conversion.

create {ANY}
	make

feature {}
	make is
		do
			create reference_points.make
		end

feature {ANY}
	ready: BOOLEAN

	build (display_width_, display_height_: INTEGER) is
		local
			uncalibrated: FAST_ARRAY[INTEGER]
		do
			display_width := display_width_
			display_height := display_height_
			from
				uncalibrated := {FAST_ARRAY[INTEGER] <<0, 0, display_width, display_height>>}
			until
				uncalibrated.is_empty
			loop
				
			end
		ensure
			ready
		end

	write_to (os: OUTPUT_STREAM) is
		require
			os.is_connected
		do
		ensure
			os.is_connected
		end

	load_from (data: INPUT_STREAM) is
		require
			data.is_connected
		do
		end

	set_offset(x_display, y_display: INTEGER) is
		do
			x_offset := x_display
			y_offset := y_display
		end
	
	convert (x_device, y_device: INTEGER) is
			-- Result is available in last_x, last_y
		require
			x_device.in_range(0, device_width)
			y_device.in_range(0, device_height)
		local
			i, j: INTEGER
			x_rest, y_rest: INTEGER
			
		do
			i := x_device // horizontal_step
			j := y_device // vertical_step
			x_rest := x_device - i * horizontal_step
			y_rest := y_device - j * vertical_step
			if y_rest * 2 < vertical_step then
				last_x := ((x_table.item(i, j) * x_rest + x_table.item(i + 1, j) * (horizontal_step - x_rest)) / horizontal_step).force_to_integer_32
			else
				last_x := ((x_table.item(i, j + 1) * x_rest + x_table.item(i + 1, j + 1) * (horizontal_step - x_rest)) / horizontal_step).force_to_integer_32
			end
			if x_rest * 2 < horizontal_step then
				last_y := ((y_table.item(i, j) * y_rest + y_table.item(i, j + 1) * (vertical_step - y_rest)) / vertical_step).force_to_integer_32
			else
				last_y := ((y_table.item(i + 1, j) * y_rest + y_table.item(i + 1, j + 1) * (vertical_step - y_rest)) / vertical_step).force_to_integer_32
			end
		ensure
			last_x.in_range(x_offset, x_offset + display_width -1)
			last_y.in_range(y_offset, y_offset + display_height - 1)
		end

	last_x, last_y: INTEGER
			-- Last conversion result (in display coordinates)
	
feature {}
	x_offset, y_offset, display_width, display_height: INTEGER
			-- coordinates and size of the displayed area in pixels

	x_table, y_table: FAST_ARRAY2[REAL]
			-- Store display coordinates for device coordinate. Use 
			-- `horizontal_step' and `vertical_step' for table indexes values.

	horizontal_step, vertical_step: INTEGER
			-- Indexes steps for tables

	device_width, device_height: INTEGER
			-- Digitizer size
	
	reference_points: REFERENCE_POINTS
			-- 4 values per reference point x_device
end