Merge pull request #17 from benoitguigal/raspi2

Raspi2

epson_printer/epsonprinter.py

@@ -1,9 +1,10 @@
 from __future__ import division
 import math
 import usb.core
-from PIL import Image
+import itertools
 from functools import wraps
-
+from multiprocessing import Pool, cpu_count
+from PIL import Image
 
 ESC = 27
 GS = 29
@@ -85,6 +86,55 @@ def set_print_speed(speed):
         speed]
     return byte_array
 
+CPU_COUNT = cpu_count()
+
+
+def marshall_stripe(stripe, w):
+    """
+    Re-arrange a 24 bits height stripe of pixels into a top to bottom then left to right array
+    See http://nicholas.piasecki.name/blog/2009/12/sending-a-bit-image-to-an-epson-tm-t88iii-receipt-printer-using-c-and-escpos/
+    :param stripe: pixels of the stripe
+    :param w: width of the stripe
+    :return:
+    """
+
+    # Calculate nL and nH
+    nh = int(w / 256)
+    nl = w % 256
+
+    data = []
+    data.extend([
+        ESC,
+        42,  # *
+        33,  # double density mode
+        nl,
+        nh])
+    for x in range(w):
+        for k in range(3):
+            slice = 0
+            for b in range(8):
+                y = (k * 8) + b
+                i = (y * w) + x
+                v = 0
+                if i < len(stripe):
+                    if stripe[i] != 255:
+                        v = 1
+                slice |= (v << (7 - b))
+
+            data.append(slice)
+
+    data.extend([
+        27,   # ESC
+        74,   # J
+        48])
+
+    return data
+
+
+def marshall_stripe_star(stripe_w):
+    """ See http://stackoverflow.com/questions/5442910/python-multiprocessing-pool-map-for-multiple-arguments """
+    return marshall_stripe(*stripe_w)
+
 
 class PrintableImage:
     """
@@ -105,54 +155,26 @@ def from_image(cls, image):
         :return:
         """
         (w, h) = image.size
+
+        # Thermal paper is 512 pixels wide
         if w > 512:
             ratio = 512. / w
             h = int(h * ratio)
             image = image.resize((512, h), Image.ANTIALIAS)
         image = image.convert('1')
         pixels = list(image.getdata())
 
-        data = []
+        nb_stripes = int(math.ceil(h / 24))
         # account for double density and page mode approximate
-        height = int(math.ceil(h / 24) * 48)
-
-        # Calculate nL and nH
-        nh = int(w / 256)
-        nl = w % 256
-
-        offset = 0
-
-        while offset < h:
-            data.extend([
-                ESC,
-                42,  # *
-                33,  # double density mode
-                nl,
-                nh])
+        height = int(nb_stripes * 48)
 
-            for x in range(w):
-                for k in range(3):
-                    slice = 0
-                    for b in range(8):
-                        y = offset + (k * 8) + b
-                        i = (y * w) + x
-                        v = 0
-                        if i < len(pixels):
-                            if pixels[i] != 255:
-                                v = 1
-                        slice |= (v << (7 - b))
-
-                    data.append(slice)
-
-            offset += 24
-
-            data.extend([
-                27,   # ESC
-                74,   # J
-                48])
-
-        return cls(data, height)
+        # Balance the data processing between different cores (this is particularly useful on Raspberry Pi 2)
+        pool = Pool(processes=CPU_COUNT)
+        stripes = [pixels[24*w*i:24*w*(i+1)] for i in range(0, nb_stripes)]
+        marshalled_stripes = pool.map(marshall_stripe_star, itertools.izip(stripes, itertools.repeat(w)))
+        merged = list(itertools.chain.from_iterable(marshalled_stripes))
 
+        return cls(merged, height)
 
     def append(self, other):
         """
@@ -165,23 +187,22 @@ def append(self, other):
         return self
 
 
-
 class EpsonPrinter:
     """ An Epson thermal printer based on ESC/POS"""
 
     printer = None
 
     def __init__(self, id_vendor, id_product, interface=0, in_ep=0x82, out_ep=0x01):
         """
-        @param idVendor  : Vendor ID
-        @param idProduct : Product ID
+        @param id_vendor  : Vendor ID
+        @param id_product : Product ID
         @param interface : USB device interface
         @param in_ep     : Input end point
         @param out_ep    : Output end point
         """
         self.interface = interface
-        self.in_ep     = in_ep
-        self.out_ep    = out_ep
+        self.in_ep = in_ep
+        self.out_ep = out_ep
 
         # Search device on USB tree and set is as printer
         self.printer = usb.core.find(idVendor=id_vendor, idProduct=id_product)
@@ -210,7 +231,6 @@ def wrapper(self, *args, **kwargs):
             self.write_bytes(byte_array)
         return wrapper
 
-
     def write_bytes(self, byte_array):
         msg = ''.join([chr(b) for b in byte_array])
         self.write(msg)