Mikkel Georgsen
1156eff896
- PrinterDriver interface: Connect/Print(bitmap,w,h)/Disconnect - ImageToRawBitmap(): 1-bit packed row-major converter from image.Image - MockDriver: saves PNG to SaveDir (/tmp default) for visual inspection - PrtQutieDriver: stub returns ErrNoDevice — safe before hardware arrives - ErrNoDevice, ErrNotConnected, ErrEmptyBitmap sentinel errors
49 lines
1.6 KiB
Go
49 lines
1.6 KiB
Go
package printer
|
|
|
|
import (
|
|
"errors"
|
|
"image"
|
|
"math"
|
|
)
|
|
|
|
// PrinterDriver is the interface all label printer implementations must satisfy.
|
|
// The PRT Qutie driver, mock driver, and any future printer use this interface.
|
|
type PrinterDriver interface {
|
|
// Connect opens the connection to the printer. Must be called before Print.
|
|
Connect() error
|
|
// Print sends a rendered label bitmap to the printer.
|
|
// bitmap is raw 1-bit packed row-major data from ImageToRawBitmap.
|
|
Print(bitmap []byte, width, height int) error
|
|
// Disconnect closes the connection.
|
|
Disconnect() error
|
|
}
|
|
|
|
var (
|
|
// ErrNoDevice is returned when no printer matching the VID/PID is found.
|
|
ErrNoDevice = errors.New("printer: no device found matching VID/PID")
|
|
// ErrNotConnected is returned when Print is called before Connect.
|
|
ErrNotConnected = errors.New("printer: not connected")
|
|
// ErrEmptyBitmap is returned when an empty or nil bitmap is passed to Print.
|
|
ErrEmptyBitmap = errors.New("printer: bitmap is empty")
|
|
)
|
|
|
|
// ImageToRawBitmap converts an image.Image to 1-bit packed row-major bitmap.
|
|
// White pixels → 0, dark pixels → 1. Returns bytes, width, and height.
|
|
func ImageToRawBitmap(img image.Image) ([]byte, int, int) {
|
|
b := img.Bounds()
|
|
w, h := b.Max.X-b.Min.X, b.Max.Y-b.Min.Y
|
|
rowBytes := int(math.Ceil(float64(w) / 8.0))
|
|
out := make([]byte, rowBytes*h)
|
|
for y := 0; y < h; y++ {
|
|
for x := 0; x < w; x++ {
|
|
r, g, bv, _ := img.At(b.Min.X+x, b.Min.Y+y).RGBA()
|
|
// Luminance: pixel is dark if average < 50% of max (0xffff).
|
|
lum := (r + g + bv) / 3
|
|
if lum < 0x7fff {
|
|
byteIdx := y*rowBytes + x/8
|
|
out[byteIdx] |= 1 << (7 - uint(x%8))
|
|
}
|
|
}
|
|
}
|
|
return out, w, h
|
|
}
|