Receipt logos: add support for black-and-white binary netpbm images. (#…

…282)

This adds a dependency on the imagesize package

.github/workflows/run-tests.yml

@@ -30,6 +30,7 @@ jobs:
           python3-cups \
           python3-dateutil \
           python3-httplib2 \
+          python3-imagesize \
           python3-odf \
           python3-psycopg2 \
           python3-qrcode \

quicktill/pdrivers.py

@@ -13,6 +13,7 @@
     _qrcode_supported = True
 except ImportError:
     _qrcode_supported = False
+import imagesize
 
 from reportlab.pdfgen import canvas
 from reportlab.lib.units import toLength
@@ -110,7 +111,18 @@ def __str__(self):
 
 class ImageElement(ReceiptElement):
     def __init__(self, image):
-        self.image_data = image
+        assert image.startswith(b"P4")  # only B&W PBM format supported
+        width, height = imagesize.get(io.BytesIO(image))
+        data_lines = [
+            line
+            for line in image.splitlines()
+            if not line.startswith(b"#")
+        ]
+        assert data_lines[0] == b"P4"
+        assert data_lines[1] == f"{width} {height}".encode("ascii")
+        self.image_data = bytes().join(data_lines[2:])
+        self.image_width = width
+        self.image_height = height
 
     def __str__(self):
         return "Image"
@@ -296,6 +308,18 @@ def _lpgetstatus(f):
         return "error light is on"  # LP_PERRORP
 
 
+def _chunks(iterable, chunk_size):
+    """Produce chunks of up-to a parameterised size from an iterable input."""
+    chunk = []
+    for item in iterable:
+        chunk.append(item)
+        if len(chunk) == chunk_size:
+            yield chunk
+            chunk = []
+    if chunk:
+        yield chunk
+
+
 class linux_lpprinter(fileprinter):
     """Print to a lp device file - /dev/lp? or /dev/usblp? on Linux
 
@@ -592,6 +616,9 @@ class escpos:
     ep_unidirectional_off = bytes([27, 85, 0])
     # follow ep_bitimage_sd with 16-bit little-endian data length
     ep_bitimage_sd = bytes([27, 42, 0])
+    ep_bitimage_dd_v24 = bytes([27, 42, 33])  # double-density, 24-dot vertical
+    ep_line_spacing_none = bytes([27, 51, 0])
+    ep_line_spacing_default = bytes([27, 50])
     ep_short_feed = bytes([27, 74, 5])
     ep_half_dot_feed = bytes([27, 74, 1])
 
@@ -689,6 +716,9 @@ def process_canvas(self, canvas, f):
                         ("%s%s%s%s%s\n" % (
                             left, ' ' * padl, center, ' ' * padr, right))
                         .encode(self.coding))
+            elif hasattr(i, 'image_data'):
+                assert 8 * len(i.image_data) == i.image_width * i.image_height
+                self._image(i.image_data, i.image_width, i.image_height, f)
             elif hasattr(i, 'qrcode_data'):
                 self._qrcode(i.qrcode_data, f)
             else:
@@ -701,6 +731,47 @@ def process_canvas(self, canvas, f):
                 f.write(escpos.ep_fullcut)
             f.flush()
 
+    def _image(self, data, width, height, f):
+        # Print a PBM bit-image
+        if width > self.dpl:
+            # Image too wide for paper
+            return
+
+        # Calculate padding required to center the image
+        padding = (self.dpl - width) // 2
+        padchars = [False] * padding
+
+        # Partition the bitmap into lines
+        lines = []
+        for chunk in _chunks(data, width // 8):
+            line = padchars.copy()
+            for byte in chunk:
+                for bit in f"{int(byte):08b}":
+                    line.append(bool(int(bit)))
+            lines.append(line)
+
+        # Compact up to twenty-four bit-lines into each row
+        rows = []
+        for linerange in _chunks(lines, 24):
+            row = []
+            for column in zip(*linerange):
+                for segment in _chunks(column, 8):
+                    binary = str().join("1" if bit else "0" for bit in segment)
+                    row.append(int(binary or "0", base=2))
+            rows.append(bytes(row))
+
+        # Write the commands to render the padded image
+        f.write(escpos.ep_line_spacing_none)
+        f.write(escpos.ep_unidirectional_on)
+        for row in rows:
+            width_info = (len(row) // 3).to_bytes(length=2, byteorder="little")
+            f.write(escpos.ep_bitimage_dd_v24 + width_info + row + b'\n')
+        f.write(escpos.ep_unidirectional_off)
+        f.write(escpos.ep_line_spacing_default)
+
+        # Clear the line for subsequent content
+        f.write(b'\r\n')
+
     def _qrcode_native(self, data, f):
         # Set the size of a "module", in dots.  The default is apparently
         # 3 (which is also the lowest).  The maximum is 16.

quicktill/printer.py

@@ -1,3 +1,5 @@
+import base64
+
 from . import td, ui, tillconfig, payment
 from decimal import Decimal
 from .models import Delivery, VatBand, Business, Transaction, PayType
@@ -25,6 +27,9 @@ def print_receipt(printer, transid):
     if not trans.lines:
         return
     with printer as d:
+        if tillconfig.publogo():
+            image = base64.b64decode(tillconfig.publogo())
+            d.printimage(image)
         d.printline(f"\t{tillconfig.pubname}", emph=1)
         for i in tillconfig.pubaddr().splitlines():
             d.printline(f"\t{i}", colour=1)

quicktill/tillconfig.py

@@ -29,6 +29,13 @@
 label_printers = []
 cash_drawer = None
 
+publogo = config.ConfigItem(
+    'core:sitelogo', None, display_name="Site logo",
+    description=(
+        "Logo image to be printed on receipts.  "
+        "To update it, use 'base64 logo.pbm | runtill config -s core:sitelogo'"
+    )
+)
 pubname = config.ConfigItem(
     'core:sitename', "Default site name", display_name="Site name",
     description="Site name to be printed on receipts")

setup.cfg

@@ -25,6 +25,7 @@ install_requires =
     pycups
     python-dateutil
     cryptography
+    imagesize ~= 1.4
 python_requires = >=3.8
 
 [options.extras_require]