Printing a graphic to a Zebra LP2844 with the GW EPL command?
I need to print an image that is being returned to me through a web service (the data is returned as RAW) and I cannot for the life of me figure out how to print a graphic to a label with EPL.
The EPL manual defines the Graphic Write instruction as:
GWp1, p2, p3, p4, DATA
All of the parameters are returned to me, so I don't have to worry about calculating the height, width, etc., but my problem is that I don't know how to format the DATA.
The manual says DATA should be
Raw binary data without graphic file formatting. Data must be in bytes.
I've tried passing a binary string and a hex string, but nothing seems to work. There is no example on how to use this command in the EPL manual and after hours of searching online I have not been able to find a single example of how to use the command (i.e. example EPL commands that I can copy & paste to send to the printer).
Does anyone have an idea of how to use this command? Could you provide me with an example? (by example I don't mean a framework, code, etc., what I mean is just the plain EPL commands).
Answer
I can confirm that the data is in raw, uncompressed binary. It is also inverted-- that is, the 0 bits print as black, at least on my UPS-firmware LP-2844. I have no idea why all the examples from Zebra show the data as encoded into a hex representation.
It's worth noting that most print servers (HP Jetdirect, Lantronix LPS1-T, and almost certainly the Zebra built-in and external print servers) will form a binary connection to the printer if you spit data at them on port 9100 (using netcat for example):
nc printer_hostname_or_ip_address 9100 < test_file.txt
You get no feedback from the printer, except for the label having printed or not.
It takes my LP-2844 (UPS Firmware) printer about 5-6 seconds to print a label containing a 816 wide x 1218 tall downloaded bitmap onto a 4" wide x 6" tall label. It seems to be all imaging time: sending three labels at once is not any faster, and the network connection (through a Lantronix LPS1-T) is held open until the final label prints. That image is at the native resolution of the printer (203 dots/inch), and there is no dithering or resizing going on (I don't think EPL2 even knows how to dither or resize).
It might be possible to speed up the imaging time by optimizing the label into many smaller bitmaps (and horizontal and vertical line segments, and perhaps filled-in rectangular blocks). This wouldn't be a very hard optimization because the image is a single-bit black and white bitmap, and the code would be fairly simple. I don't know if it would really speed it up, though.
A more modern Zebra GX420 running ZPL with a built-in ethernet port ($500 online) can print the same label (with essentially the same graphic download encoding) in 1-2 seconds.
By the way, since I haven't yet actually answered the question, the raw EPL code for this is:
(a blank line)
N
q816
Q1218,20
GW10,10,102,1218,(124236 bytes of inverted bitmap data)
P
all the newlines are 0x0a (unix-style).