escpos-go-labels/main.go

package main

import (
    "fmt"
    "github.com/kenshaw/escpos"
    "math"
    "net/http"
    "os"
    "time"
)

const ESC = byte(27)

func pageWidth(widht int) []byte {
	return []byte{escpos.GS, 87, byte(widht), 0}
}
func pageMargin(margin int) []byte {
	return []byte{escpos.GS, 76, byte(margin), 0}
}
func pageMode() []byte {
	return []byte{ESC, 'L'}
}
func pageDirection(direction uint8) []byte {
	// https://www.epson-biz.com/modules/ref_escpos/index.php?content_id=55
	return []byte{ESC, 'T', direction}
}
func pagePrintArea(x, y, width, height int) []byte {
	return []byte{ESC, 'W',
		byte(x & 255), byte(x >> 8 & 255),
		byte(y & 255), byte(y >> 8 & 255),
		byte(width & 255), byte(width >> 8 & 255),
		byte(height & 255), byte(height >> 8 & 255)}
}
func offsetY(offset int) []byte {
	// A positive number specifies movement downward, and a negative number specifies movement upward.
	// The horizontal or vertical motion unit is used for the print direction set by ESC T.
	// When the starting position is set to the upper left or lower right of the print area using ESC T, the vertical motion unit is used.
	// When the starting position is set to the upper right or lower left of the print area using ESC T, the horizontal motion unit is used.
	return []byte{escpos.GS, '\\', byte(offset & 255), byte(offset >> 8 & 255)}
}
func offsetX(offset int) []byte {
	// A positive number specifies movement to the right, and a negative number specifies movement to the left.
	// When Standard mode is selected, the horizontal motion unit is used.
	// when Page mode is selected, the horizontal or vertical motion unit is used for the print direction set by ESC T.
	// When the starting position is set to the upper left or lower right of the print area using ESC T, the horizontal motion unit is used.
	// When the starting position is set to the upper right or lower left of the print area using ESC T, the vertical motion unit is used.
	return []byte{ESC, '\\', byte(offset & 255), byte(offset >> 8 & 255)}
}
func invert(n int) []byte {
	//When the LSB of n is 0, white/black reverse print mode is turned off.
	//n = 0 – 255
	return []byte{escpos.GS, byte('B'), byte(n)}
}
func disableSensors() []byte {
	return []byte{ESC, 'c', '3', 0}
}
func printSpeed(m int) []byte {
	// 	m = 0 – 9, 48 – 57 : slowest - fastest
	// [Default] 0 = Setting value of GS ( E   <Function 5> customize value (a = 6)
	// m = 0
	//Slower print speed seems to retain a bit more quality in dithered images. pure B/W images do not have a noticable difference
	return []byte{escpos.GS, '(', 'K', 2, 0, 50, byte(m & 255), byte(m >> 8 & 255)}
}

func main() {
    f, err := os.OpenFile("/dev/usb/lp0", os.O_WRONLY|os.O_CREATE, 0)
    if err != nil {
        panic(err)
    }
    defer f.Close()

    ep := escpos.New(f)
    ep.Init()

    http.HandleFunc("/create_dnh_label", func(w http.ResponseWriter, r *http.Request) {
        createDnhLabelHandler(w, r, ep)
    })

    fmt.Println("Server starting on port 8080")
    if err := http.ListenAndServe(":8080", nil); err != nil {
        panic(err)
    }
}

func createDnhLabelHandler(w http.ResponseWriter, r *http.Request, ep *escpos.Escpos) {
    if r.Method != http.MethodPost {
        http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
        return
    }

    name := r.FormValue("name")
    date := r.FormValue("date")

    // Check if name is blank
    if name == "" {
        http.Error(w, "Name cannot be blank", http.StatusBadRequest)
        return
    }

    // Set date to today if not defined
    if date == "" {
        date = time.Now().Format("2006-01-02")
    }

    // Here you can add the logic for creating a label using the POST data
    text := fmt.Sprintf("%s - %s \n", name, date)
    ep.Init()
    ep.WriteRaw(pageMode())
    ep.WriteRaw(pageDirection(1))
    ep.WriteRaw(pagePrintArea(0, 0, int(math.Round((29.0/80.0)*512)), 850))
    ep.WriteRaw(offsetY(30))
    ep.SetFontSize(1, 1)
    ep.Write("Technologia Incognita\n")
    ep.WriteRaw(offsetY(35))
    ep.SetFontSize(3, 2)
    ep.SetEmphasize(1)
    ep.Write("Do Not Hack\n")
    ep.SetEmphasize(0)
    ep.WriteRaw(offsetY(15))
    ep.SetFontSize(1, 1)
    ep.Write(text)
    ep.WriteRaw([]byte{12}) // FF: in Page mode, prints all the data in the print buffer collectively and switches from Page mode to Standard mode.
    ep.Cut()
    ep.End()
    w.WriteHeader(http.StatusOK)
}