Add ability to alter brightness

Author: hkeward

README.md

@@ -100,3 +100,5 @@ printer.close()
 ### Sending images to the printer
 
 Format: `phomemo_printer -a bluetooth_address -c bluetooth_channel -i "/path/to/image.png"`
+
+You can increase or decrease the brightness of the image using `-b <float>` - numbers < 1.0 decrease the brightness, and > 1.0 increase it.

phomemo_printer/ESCPOS_printer.py

@@ -2,7 +2,7 @@
 from .pixel_sans.charset import charset
 from .ESCPOS_constants import *
 import socket
-from PIL import Image
+from PIL import Image, ImageEnhance
 
 
 class Printer:
@@ -140,12 +140,13 @@ def print_charset(self):
         self.print_text(char_string_split)
 
     # from https://github.com/vivier/phomemo-tools
-    def print_image(self, image_path):
+    def print_image(self, image_path, brightness=None):
         """
             Print an image
 
             Args:
                 image_path (str): Path to an image file to print
+                brightness (float): Optionally decrease (< 1.0) or increase (> 1.0) image brightness
         """
         image = Image.open(image_path)
         if image.width > image.height:
@@ -158,6 +159,10 @@ def print_image(self, image_path):
             size=(IMAGE_WIDTH_BITS, int(image.height * IMAGE_WIDTH_BITS / image.width))
         )
 
+        if brightness is not None:
+            filter = ImageEnhance.Brightness(image)
+            image = filter.enhance(brightness)
+
         # black&white printer: dithering
         image = image.convert(mode="1")
 

phomemo_printer/command_line.py

@@ -11,7 +11,7 @@ def main(args):
     elif args.text:
         printer.print_text(args.text)
     elif args.image:
-        printer.print_image(args.image)
+        printer.print_image(args.image, args.brightness)
 
     printer.close()
 
@@ -50,6 +50,13 @@ def cli():
         help="The channel to connect to your bluetooth device on",
         required=True,
     )
+    parser.add_argument(
+        "-b",
+        "--brightness",
+        type=float,
+        help="Optionally alter image brightness before printing (< 1.0 - decrease brightness; > 1.0 - increase brightness)",
+        required=False,
+    )
 
     args = parser.parse_args()
     main(args)