CTTP which stand for convert to thermal printer (file) is a tiny command line program to convert images files to data files which can by printed by a thermal printer. It also provide several builtin tools to manipultate input image.

Table of content

• Table of content
• Prerequisites
  • ImageMagick
  • Ruby
  • Bundler
• CTTP
  • Installation
  • Usage
    • In a file
    • In memory
    • Arduino examples

Prerequisites

ImageMagick

Installation:

sudo apt install imagemagick libmagick++-dev

Verification:

$ convert --version
Version: ImageMagick 6.9.7-4 Q16 x86_64 20170114 http://www.imagemagick.org

Ruby

Install rbenv:

curl -fsSL https://github.com/rbenv/rbenv-installer/raw/master/bin/rbenv-installer | bash

Add rbenv to path in .bashrc and install ruby (current latest 2.5.3):

echo 'export PATH="$PATH:$HOME/.rbenv/bin"' >> ~/.bashrc
echo 'eval "$(rbenv init -)"' >> ~/.bashrc
source ~/.basrc
rbenv install 2.5.3

Bundler

Install bundler:

gem install bundler
rbenv rehash

CTTP

Installation

git clone https://github.com/henricazottes/cttp.git
cd cttp/
bundle install

Usage

-h, --help: show help

-o filename, --output filename: Save data in an ouput file named filename; must follow 8.3 format (8 max char name + 3 max char extension max) for arduino SD module compatibility Default filename is data

-a, --array: Print the data in a C++ array form like: data: {0x00, ...}

-i, --info: Print converted image dimensions and size

-r x, --rotate x: rotate the image by x degrees

--flip_h: flip the image horizontally

--flip_v: flip the image vertically

Important: Image size may be changed so the width is divisible by 8 for compatibility purpose with the printer. Use -i to output the final dimensions.

In a file

Use -o to create a data file ready to be copied on an SD card. See example below to see how to print it.

In memory

Use -a to output the data array. Copy and paste it in your arduino sketch as follow.

Arduino examples

First run cttp with your image:

$ ./cttp.rb img_test.png -o -i -a
data:   {0xf0,0x01,0xf0,0x00,0xf0,0x00,0xf0,0x00,0x0f,0x00,0x0f,0x00,0x0f,0x00,0x0e,0x00,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff}
size:   32 bytes
width:  16 px
height: 16 px

Note the image size and copy the data file to sd card / or copy the data array from terminal. Here is the arduino sketch to print it using Adafruit library:

#include <Adafruit_Thermal.h>
#include <SD.h>
#include "SoftwareSerial.h"

#define TX_PIN 9 // Arduino transmit  YELLOW WIRE  labeled RX on printer
#define RX_PIN 8 // Arduino receive   GREEN WIRE   labeled TX on printer
#define SD_Pin 4

SoftwareSerial mySerial(RX_PIN, TX_PIN); // Declare SoftwareSerial obj first
Adafruit_Thermal printer(&mySerial);     // Pass addr to printer constructor

inline void initSD() {
  pinMode(SD_Pin, OUTPUT);
  if (!SD.begin(SD_Pin)) {
    Serial.println("SD Error");
  } else {
    Serial.println("SD Ok");
  }
}

void setup() {
  initSD();

  mySerial.begin(19200);  // Initialize SoftwareSerial
  printer.begin();        // Init printer (same regardless of serial type)

  // From file on SD card
  File data = SD.open("data", FILE_READ);
  printer.printBitmap(16, 16, dynamic_cast<Stream*>(&data));
  data.close();
  printer.feed(2);

  // From array directly in memory
  const uint8_t test[] = {0xf0,0x01,0xf0,0x00,0xf0,0x00,0xf0,0x00,0x0f,0x00,0x0f,0x00,0x0f,0x00,0x0e,0x00,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff,0x00,0xff};
  printer.printBitmap(16, 16, test);
  printer.feed(2);

  printer.sleep();      // Tell printer to sleep
  delay(3000L);         // Sleep for 3 seconds
  printer.wake();       // MUST wake() before printing again, even if reset
  printer.setDefault(); // Restore printer to defaults
  
}

void loop() {
}