Lua Requires Chilkat v11.7.0+

QR Code Error Correction Levels

See more QR Code Examples

Demonstrates the four QR error-correction levels. L, M, Q and H allow a reader to recover the data when about 7%, 15%, 25% and 30% of the symbol is damaged or covered. More error correction leaves less room for data, so the same text needs a larger symbol at a higher level. The default is M. The example also shows boostErrorCorrection, which raises the level for free when the chosen version has room to spare. Lua

local chilkat = require("chilkat")

local success = false

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

local fmt = chilkat.Formats.new()
local json = chilkat.JsonObject.new()
local jsonOut = chilkat.JsonObject.new()
json:update_string("payload.text", "https://www.chilkatsoft.com/barcode_overview.asp")

-- Encode the same text at each level.
local levels = chilkat.JsonArray.new()
levels:load("[\"L\",\"M\",\"Q\",\"H\"]")
for i = 0, 3 do
    json:update_string("encoding.qr.errorCorrection", levels:string_at(i))
    success = fmt:qr_code("generate", json, jsonOut)
    if not success then
        print(fmt.last_error_text)
        return
    end

    print("level " .. levels:string_at(i) .. ": version " .. jsonOut:int_of("symbols[0].selectedEncoding.version") .. ", " .. jsonOut:int_of("symbols[0].dimensions.modulesWide") .. " modules wide")
end

-- The four symbols.  They hold the same text, and the higher the level, the larger the symbol:

-- 

-- A symbol often has room left over.  boostErrorCorrection uses it: the level is raised
-- as far as the same version allows, so the symbol is no larger but is more robust.
local json2 = chilkat.JsonObject.new()
json2:update_string("payload.text", "https://chilkatsoft.com")
json2:update_string("encoding.qr.errorCorrection", "L")
success = fmt:qr_code("generate", json2, jsonOut)
if not success then
    print(fmt.last_error_text)
    return
end

print("level L requested: version " .. jsonOut:int_of("symbols[0].selectedEncoding.version") .. ", level " .. jsonOut:string_of("symbols[0].selectedEncoding.errorCorrection"))

json2:update_bool("encoding.qr.boostErrorCorrection", true)
success = fmt:qr_code("generate", json2, jsonOut)
if not success then
    print(fmt.last_error_text)
    return
end

print("level L with boost: version " .. jsonOut:int_of("symbols[0].selectedEncoding.version") .. ", level " .. jsonOut:string_of("symbols[0].selectedEncoding.errorCorrection"))

-- Level L, and level M reached by the boost.  The two symbols are the same size:

-- 

-- Sample output:

-- level L: version 3, 29 modules wide
-- level M: version 4, 33 modules wide
-- level Q: version 5, 37 modules wide
-- level H: version 6, 41 modules wide
-- level L requested: version 2, level L
-- level L with boost: version 2, level M