Lua Requires Chilkat v11.7.0+

QR Code with a Text Caption

See more QR Code Examples

Demonstrates printing a line of text under a QR code, such as the order number or the address the code holds, so that a person can read it too. render.text turns the caption on and gives its value, which is printable ASCII and is drawn in a built-in font that needs no font files. The caption can go above or below the symbol, be aligned left, center or right, and be scaled. 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", "https://www.chilkatsoft.com/order/12345")
json:update_int("render.moduleSize", 6)

-- The caption.  It need not be the same as the text in the QR code.
json:update_bool("render.text.enabled", true)
json:update_string("render.text.value", "ORDER 12345")
-- position is "below" (the default) or "above".  alignment is "center" (the default), "left" or "right".
json:update_string("render.text.position", "below")
-- Each dot of the caption's font is drawn this many pixels wide.
json:update_int("render.text.scale", 3)

json:update_string("output.path", "qa_output/qr_caption.png")
json:update_bool("output.overwrite", true)
json:update_string("output.return", "none")

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

print("caption: " .. jsonOut:string_of("measurements[0].text"))
print("caption scale: " .. jsonOut:int_of("measurements[0].textScale"))
print("height added for the caption: " .. jsonOut:int_of("measurements[0].textBandPx") .. " pixels")
print("image: " .. jsonOut:int_of("measurements[0].canvasWidth") .. " x " .. jsonOut:int_of("measurements[0].canvasHeight") .. " pixels")

-- The image written to qa_output/qr_caption.png:

-- 

-- Sample output:

-- caption: ORDER 12345
-- caption scale: 3
-- height added for the caption: 21 pixels
-- image: 222 x 243 pixels