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 :-)
png2pos conforms to ESC/POS language used by these printers:
- Epson TM-T70 (tested)
- Epson TM-T88III/IV
- Epson TM-T90
- Epson TM-L90
- Epson TM-P60
- Epson TM-J2000/J2100 (deprecated)
- PRT PT562A-B (tested)
- PRT PT802A-B (tested)
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 CIE, 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. Unfortunately I am unable to provide you with free support. If you like png2pos and use it, please let me know, it motivates me in further development.
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.
There are available prepared builds for some common platforms in Releases section.
Please, if you use GPG, verify also attached GPG signature:
Import public key into temporary keyring (you can import it into your permanent keyring of course) and verify ZIP file's ASC signature:
$ curl https://forers.com/494CD31C.asc | gpg --no-default-keyring --keyring ./gpg-png2pos.tmp --import ↵
gpg: key 494CD31C: public key "Petr Kutalek <petr.kutalek@forers.com>" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
$ gpg --no-default-keyring --keyring ./gpg-png2pos.tmp --verify png2pos-v1.5.4-rpi.zip.asc ↵
gpg: Signature made Thu Jan 1 20:42:13 2015 CET using RSA key ID 494CD31C
gpg: Good signature from "Petr Kutalek <petr.kutalek@forers.com>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.
Primary key fingerprint: 06EB BE07 4850 3817 8533 B45D C1D9 23EB 494C D31C
$ rm ./gpg-png2pos.*
If you prefer to build binary file yourself, clone the source code:
$ git clone https://github.com/petrkutalek/png2pos.git ↵
$ cd png2pos ↵
$ git submodule init ↵
$ git submodule update ↵
To build and install binary just type:
$ make install-strip ↵
On Mac typically you can use clang preprocessor:
$ make CC=clang install-strip ↵
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-strip ↵
Windows binary is build in MinGW by (MinGW must be included in PATH):
C:\devel\png2pos> mingw32-make -f Makefile.win strip
Please, do not forget to specify your printer's head width in pixels via PRINTER_MAX_WIDTH constant if it differs from default value of 512 px. (You probably need to specify 384 for 56 mm printers.) PRINTER_MAX_WIDTH must be divisible by 8.
| target | make will build… |
|---|---|
| (empty) | png2pos |
| clean | (removes intermediate products) |
| man | compressed man page |
| strip | stripped version (suggested) |
| profiled | profiled version (up to 3 % performance gain on repeat tasks) |
| install | install png2pos into PREFIX (default /usr/local) |
| install-strip | install stripped version into PREFIX (default /usr/local) |
| debug | debug version (creates PNG temp file after each step in processing chain) |
| rpi | Raspberry Pi optimized version |
| static | static binary (does not work on OS X, see Makefile) |
| analyze | clang static analyzer (OS X) |
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
Greyscale version
Pre-processed version (Histogram Equalization Algorithm)
Produced B/W dithered version (Atkinson Dithering Algorithm)
Histograms (raw and pre-processed image)
