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-- NDWI
function init()
--create an empty image for the LUT
img_lut = image_t.new()
--load the LUT
image_load_png(img_lut, get_resource_path("lut/NDWI.png"), false)
--return 3 channels, RGB
return 3
end
function process()
for x = 0, rgb_output:width() - 1, 1 do
for y = 0, rgb_output:height() - 1, 1 do
--get channels from satdump.json
get_channel_values(x, y)
local cch2 = get_channel_value(0)
local cch3a = get_channel_value(1)
--perform NDWI
local ndwi = (cch2-cch3a)/(cch2+cch3a)
--range convert from -1 -> 1 to 0 -> 256
local ndwi_lutval = (((ndwi-(-1))*256) / (1-(-1)))
--sanity checks (noise)
if ndwi_lutval < 0 then
ndwi_lutval = 0
end
if ndwi_lutval > 255 then
ndwi_lutval = 255
end
--don't forget to create a table!
local lut_result = {}
--send the ndwi_lutval to the LUT, retrieve it back in the table as 3 R,G,B channels
lut_result[0] = img_lut:get(0 * img_lut:height() * img_lut:width() + ndwi_lutval * img_lut:width() + ndwi_lutval) / 255.0
lut_result[1] = img_lut:get(1 * img_lut:height() * img_lut:width() + ndwi_lutval * img_lut:width() + ndwi_lutval) / 255.0
lut_result[2] = img_lut:get(2 * img_lut:height() * img_lut:width() + ndwi_lutval * img_lut:width() + ndwi_lutval) / 255.0
--return RGB 0=R 1=G 2=B
set_img_out(0, x, y, lut_result[0])
set_img_out(1, x, y, lut_result[1])
set_img_out(2, x, y, lut_result[2])
end
--set the progress bar accordingly
set_progress(x, rgb_output:width())
end
end
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