lua-resty-qrcode

LuaJIT FFI QR Code Generation

This module utilizes LuaJIT's FFI to bind to libqrencode, cairo and gd libraries, providing efficient functions for generating QR code images in various formats.

Features

• Generates QR codes in SVG, PNG (using Cairo or GD), and Base64 encoded PNG formats.
• Allows customization of margins, cell size, and scale.
• Leverages FFI for performance optimization.

Functions

generate_qr_code_svg(text, margin)

Generates an SVG representation of a QR code.

• text: The text to encode in the QR code. Defaults to "Hello, World!".
• margin: The margin around the QR code in cells. Defaults to 4.

Returns: A string containing the SVG data.

create_red_image_base64()

Creates a simple red square image encoded in Base64. This function serves as a demonstration of using Cairo to create and encode images.

Returns: A string containing the Base64 encoded PNG data.

generate_qr_code_cairo_png(text, margin, cellSize)

Generates a PNG image of a QR code using the Cairo graphics library.

• text: The text to encode in the QR code. Defaults to "Hello, World!".
• margin: The margin around the QR code in cells. Defaults to 1.
• cellSize: The size of each module in the QR code, in pixels. Defaults to 2.

Returns: A string containing the Base64 encoded PNG data.

generate_qr_code_gd_png(text, scale)

Generates a PNG image of a QR code using the GD graphics library.

• text: The text to encode in the QR code. Defaults to "Hello, World!".
• scale: The scaling factor for the QR code image. Defaults to 1. Note: Using scales greater than 5 can impact performance.

Returns: A string containing the Base64 encoded PNG data.

Example Usage

local ffi_qrencode = require("ffi_qrencode")
local base_encoding = require("resty.base_encoding")

-- Generate an SVG QR code
local svg_qr = ffi_qrencode.generate_qr_code_svg("This is a test", 2)
ngx.say(svg_qr)

-- Generate a PNG QR code using Cairo
local png_qr_cairo = ffi_qrencode.generate_qr_code_cairo_png("Cairo QR Code", 3, 4)
ngx.header.content_type = "image/png"
ngx.print(base_encoding.decode_base64(png_qr_cairo))

-- Generate a PNG QR code using GD
local png_qr_gd = ffi_qrencode.generate_qr_code_gd_png("GD QR Code", 2)
ngx.header.content_type = "image/png"
ngx.print(base_encoding.decode_base64(png_qr_gd))

Dependencies

• LuaJIT
• libqrencode
• libcairo
• libgd
• resty.base_encoding

Installation

1. Ensure the required libraries are installed on your system.
2. Copy the qrcode.lua file to your project.
3. Require the module in your Lua code:

local ffi_qrcode = require("qrcode")

Notes

• Error handling is implemented to provide informative messages in case of failures.
• The generate_qr_code_cairo_png function includes dynamic buffer allocation to handle potentially larger image sizes.
• The module prioritizes performance optimization through FFI and careful memory management.
• Code readability is maintained while still focusing on efficiency.

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