Lua Requires Chilkat v11.7.0+

Get the Modules of a QR Code (Bit Matrix)

See more QR Code Examples

Demonstrates getting the QR code itself, as a grid of dark and light modules, to draw with something other than the built-in PNG and SVG output: on a canvas, in a PDF, on a display, or with a label printer language. With output.includeModuleData the response has symbols[0].moduleData, a bit matrix with one bit per module, each row starting on a new byte, most significant bit first, 1 for dark. The quiet zone is not part of the matrix. The example prints the symbol using two characters per module. Lua

local chilkat = require("chilkat")

-- This example requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.

local json = chilkat.JsonObject.new()
json:update_string("payload.text", "CHILKAT")
json:update_bool("output.includeModuleData", true)

local fmt = chilkat.Formats.new()
local jsonOut = chilkat.JsonObject.new()
local success = fmt:qr_code("generate", json, jsonOut)
if not success then
    print(fmt.last_error_text)
    return
end

local width = jsonOut:int_of("symbols[0].moduleData.width")
local height = jsonOut:int_of("symbols[0].moduleData.height")
local rowBytes = jsonOut:int_of("symbols[0].moduleData.rowBytes")
print("kind: " .. jsonOut:string_of("symbols[0].moduleData.kind"))
print("modules: " .. width .. " x " .. height .. ", " .. rowBytes .. " bytes per row")

-- The matrix is height rows of rowBytes bytes.
local bd = chilkat.BinData.new()
success = bd:append_encoded(jsonOut:string_of("symbols[0].moduleData.bytesBase64"), "base64")
if not success then
    print(bd.last_error_text)
    return
end

local sbRow = chilkat.StringBuilder.new()
local b = 0
local mask = 128
for row = 0, height - 1 do
    sbRow:clear()
    for col = 0, width - 1 do
        -- The module at (col,row) is a bit of the byte at (row * rowBytes) + (col / 8).
        -- The leftmost module of each byte is its most significant bit.
        if (col % 8) == 0 then
            mask = 128
        end

        b = bd:get_byte((row * rowBytes) + (math.floor(col / 8)))
        if ((math.floor(b / mask)) % 2) == 1 then
            sbRow:append("##")
        else
            sbRow:append("  ")
        end

        mask = math.floor(mask / 2)
    end

    print(sbRow:get_as_string())
end

-- The same symbol as the PNG that the call also returned:

-- 

-- Sample output:

-- kind: bitMatrix
-- modules: 21 x 21, 3 bytes per row
-- ##############              ##############
-- ##          ##      ####    ##          ##
-- ##  ######  ##  ##  ####    ##  ######  ##
-- ##  ######  ##  ##          ##  ######  ##
-- ##  ######  ##  ##  ##  ##  ##  ######  ##
-- ##          ##  ####  ##    ##          ##
-- ##############  ##  ##  ##  ##############
--                 ####
-- ##  ##########      ####    ##########
--     ####          ##  ########    ######
-- ####  ########    ####  ##  ####      ####
--       ##  ##      ############    ####  ##
--   ######  ####  ######  ##    ##  ##
--                 ##  ##  ##    ##  ##    ##
-- ##############        ##  ##    ##      ##
-- ##          ##  ##  ##        ######  ####
-- ##  ######  ##  ####  ##  ##    ##
-- ##  ######  ##  ##  ############    ##
-- ##  ######  ##  ##      ##  ####  ##
-- ##          ##    ##  ########          ##
-- ##############  ##      ##      ######