NOTE: png2pos fulfills its purpose and does it well. I do not intend to develop it any more. It is licensed under MIT: anyone can use it for free, anyone has the right to modify it unless the name "png2pos" is being used for further releases.
png2pos is a utility to convert PNG images to ESC/POS format (printer control codes and escape sequences) used by POS thermal printers. Output file can be just sent to printer.
png2pos does not contain any Epson drivers, it is not a driver/filter replacement… png2pos is just a utility for embedded projects, for whose printing PNG files is sufficient and ideal lightweight solution.
png2pos is:
- free and open-source
- rock stable
- highly optimized, fast, tiny and lightweight (few KiBs binary, no lib dependencies)
- secure (does not require any escalated privileges)
- using high-quality algorithms
- easy to use
- multiplatform (tested on Linux — x86 and ARM/Raspberry Pi, OS X and Windows)
- well tested
- 100% handcrafted in Prague, CZ :-)
In file print.cmd replace PRINTER with your printer's device. Now you can drag & drop your PNG file into this shortcut to directly print it on your thermal printer. For further details, please check this blog post.
It accepts any PNG file (B/W, greyscale, RGB, RGBA), applies Histogram Equalization Algorithm and via Atkinson Dithering Algorithm converts it to B/W bitmap wrapped by ESC/POS commands.
ESC/POS is a printer language. The “POS” stands for “Point of Sale”, the “ESC” stands for “escape” because command instructions are escaped with a special characters. png2pos utilizes ESC@, GSV, GSL, GS8L and GS(L ESC/POS commands. It also prepends needed printer initialization binary sequences and adds paper cutoff command, if requested.
png2pos requires 5 × WIDTH (rounded up to multiple of 8) × HEIGHT bytes of RAM. (e.g. to process full-width image of receipt 768 pixels tall you need about 2 MiB of RAM.)
png2pos converts RGBA images into greyscale version via algorithm compliant with ITU-R, BT.709. (RGBA → RGB → R'G'B' (gamma 2.2) → luma Y' → lightness L*). For performance reasons png2pos uses pre-calculated lookup tables and integer based math.
png2pos is free MIT-licensed software provided as is. If you like png2pos and use it, please let me know, it motivates me in further development.
Unfortunately I am unable to provide you with free support. Please, do not ever ask me to assist you with source code modifications or to make a special build for you etc., if you use png2pos for your business (especially if you have not donated to its development). It is your job you are paid for.
Important: png2pos will never ever be like Emacs; it is simple and specialized utility.
There is also an alternative project called png2escpos created by The Working Group Inc. It's younger, simpler and uses libpng. png2pos is in all aspects mature, nevertheless you may like alternative even more.
You have to build binary file yourself. Clone the source code:
$ git clone --recursive https://github.com/petrkutalek/png2pos.git ↵
$ cd png2pos ↵
To build and install binary just type:
$ make install ↵
On Mac typically you can use clang preprocessor:
$ make CC=clang install ↵
On Linux you can also build static binary (e.g. also based on musl):
$ make CC=/usr/local/musl/bin/musl-gcc static ↵
$ make install ↵
Windows binary is build in MinGW by (MinGW must be included in PATH):
C:\devel\png2pos> mingw32-make -f Makefile.win strip
png2pos has no lib dependencies and is easy to build and run on Linux, Mac and Windows.
$ png2pos -c -r /tmp/*.png > /dev/usb/lp0 ↵
Original (3 bytes per pixel)
Greyscale version (1 byte per pixel)
Post-processed version (Histogram Equalization Algorithm, 1 byte per pixel)
Produced B/W dithered version (Atkinson Dithering Algorithm, 1 bit per pixel)
Histograms (raw and post-processed image)
