esc-pos-encoder
Create a set of commands that can be send to any receipt printer that supports ESC/POS
Usage
First, install the package using npm:
npm install esc-pos-encoder --save
Then, require the package and use it like so:
let EscPosEncoder = require('esc-pos-encoder');
let encoder = new EscPosEncoder();
let result = encoder
.initialize()
.text('The quick brown fox jumps over the lazy dog)
.newline()
.qrcode('https://nielsleenheer.com')
.encode();
All commands can be chained, except for encode() which will return the result as an Uint8Array which contains all the bytes that need to be send to the printer.
You can reuse the instantiated EscPosEncoder class to generate multiple commands or sets of commands for the same printer. It will remember settings like code page, so you don't have to specify that on subsequent use. That does rely on that previous commands were actually send to the printer.
The following commands are available:
Initialize
Properly initialize the printer, which means text mode is enabled and settings like code page are set to default.
let result = encoder
.initialize()
.encode()
Codepage
Set the code page of the printer. Receipt printers don't support UTF-8 or any other unicode encoding, instead the rely on legacy code pages.
If you specify the code page, it will send a command to the printer to enable that particular code page and from then on it will automatically encode all text string to that code page.
If you don't specify a code page, it will assume you want to print only ASCII characters and strip out any others.
let result = encoder
.codepage('windows1251')
.text('Iñtërnâtiônàlizætiøn')
.encode()
The following code pages are supported: cp437, cp737, cp850, cp775, cp852, cp855, cp857, cp858, cp860, cp861, cp862, cp863, cp864, cp865, cp866, cp869, cp1252, iso88596, windows1250, windows1251, windows1252, windows1253, windows1254, windows1255, windows1256, windows1257, windows1258.
Text
Print a string of text. If the text is longer than the line width of the printer, it will automatially wrap to the next line when it reaches the maximum width. That means it could wrap right in the middle of a word.
let result = encoder
.text('The quick brown fox jumps over the lazy dog')
.encode()
An optional parameter turns on word wrapping. To enable this, specify the maximum length of the line.
let result = encoder
.text('The quick brown fox jumps over the lazy dog', 20)
.encode()
Newline
Move to the beginning of the next line.
let result = encoder
.newline()
.encode()
Line
Print a line of text. This is similar to the text() command, except it will automatically add a newline() command.
let result = encoder
.line('The is the first line')
.line('And this is the second')
.encode()
This would be equal to:
let result = encoder
.text('The is the first line')
.newline()
.text('And this is the second')
.newline()
.encode()
An optional parameter turns on word wrapping. To enable this, specify the maximum length of the line.
let result = encoder
.line('The quick brown fox jumps over the lazy dog', 20)
.encode()
Underline
Change the text style to underline.
let result = encoder
.text('This is ')
.underline()
.text('underlined')
.underline()
.encode()
It will try to remember the current state of the text style. But you can also provide and additional parameter to force the text style to turn on and off.
let result = encoder
.text('This is ')
.underline(true)
.text('bold')
.underline(false)
.encode()
Bold
Change the text style to bold.
let result = encoder
.text('This is ')
.bold()
.text('underlined')
.bold()
.encode()
It will try to remember the current state of the text style. But you can also provide and additional parameter to force the text style to turn on and off.
let result = encoder
.text('This is ')
.bold(true)
.text('bold')
.bold(false)
.encode()
Align
Change the align text style.
let result = encoder
.align('center')
.text('This is center align')
.align('right')
.text('This is right align')
.align('left')
.text('This is left align')
.encode()
Italic
Change the text style to italic.
let result = encoder
.text('This is ')
.italic()
.text('italic text')
.italic()
.encode()
It will try to remember the current state of the text style. But you can also provide and additional parameter to force the text style to turn on and off.
let result = encoder
.text('This is ')
.italic(true)
.text('italic text')
.italic(false)
.encode()
Cut
POS printer will cut the paper to separate tickets.
let result = encoder
.line('This is the first line')
.cut('partial-cut')
.line('This is the second line')
.cut('full-cut')
.encode()
Size
Change the text size. You can specify the size using a parameter which can be either "small" or "normal".
let result = encoder
.size('small')
.line('A line of small text)
.size('normal')
.line('A line of normal text)
.encode()
CharSize
Change the char size. Set the size of text, as a multiple of the normal size. Width and Height range are 1-8
let result = encoder
.charSize(5,5)
.line('A line of size x 5 text)
.charSize(1,1)
.line('A line of normal text)
.encode()
Barcode
Print a barcode of a certain symbology. The first parameter is the value of the barcode, the second is the symbology and finally the height of the barcode.
The following symbologies can be used: 'upca', 'ean13', 'ean8', 'code39', 'itf', 'codabar'.
let result = encoder
.barcode('3130630574613', 'ean13', 60)
.encode()
Qrcode
Print a QR code. The first parameter is the value of the QR code.
let result = encoder
.qrcode('https://nielsleenheer.com')
.encode()
Image
Print an image. The image is automatically converted to black and white and can optionally be dithered using different algorithms.
The first parameter is the image itself. When running in the browser it can be any element that can be drawn onto a canvas, like an img, svg, canvas and video elements. When on Node it can be a Canvas provided by the canvas package.
The second parameter is the width of the image on the paper receipt in pixels. It must be a multiple of 8.
The third parameter is the height of the image on the paper receipt in pixels. It must be a multiple of 8.
The fourth parameter is the dithering algorithm that is used to turn colour and grayscale images into black and white. The follow algorithms are supported: threshold, bayer, floydsteinberg, atkinson. If not supplied, it will default to a simple threshold.
The fifth paramter is the threshold that will be used by the threshold and bayer dithering algorithm. It is ignored by the other algorithms. It is set to a default of 128.
The sixth parameter is to draw the inverse image. It is set to a default of false.
let img = new Image();
img.src = 'https://...';
img.onload = function() {
let result = encoder
.image(img, 0, 0,300, 300, 'atkinson')
.encode()
}
License
MIT