implement send_to_printer

add dithering to image preview

iwii_photobooth.py

@@ -12,6 +12,7 @@ from pathlib import Path
 from platform import system
 
 from PIL import ImageOps 
+from PIL.ImagePalette import ImagePalette
 from PIL.ImageTk import Image, PhotoImage
 from serial import Serial
 
@@ -20,7 +21,18 @@ IWII_RESOLUTION = Resolution(576, 720)
 
 SUPPORTED_IMAGE_TYPES = sorted("*"+ext for ext, type_ in Image.registered_extensions().items() if type_ in ("PNG", "GIF", "JPEG", "WEBP", "BMP"))
 
-def widget_action(func: Callable):
+IWII_PALETTE = ImagePalette(
+    "P",
+    [
+        255, 255, 255, #white
+        0, 255, 255, #cyan
+        255, 0, 255, #magenta
+        255, 255, 0, #yellow
+        0, 0, 0, #black
+    ]
+)
+
+def widget_action(func: Callable[[Event], None]) -> Callable[[Event], None]:
     # decorator to wrap widget actions in an error handler that displays exceptions in error message windows
     @wraps(func)
     def wrapper(event: Event):
@@ -43,13 +55,14 @@ def widget_action(func: Callable):
                 parent=event.widget.master
             )
             
-            event.widget.master.quit()
+            quit_photobooth(event)
+            exit(1)
     
     return wrapper
 
 
 @widget_action
-def open_preview(event: Event):
+def open_preview(event: Event) -> None:
     file = filedialog.askopenfilename(
         parent=event.widget.master,
         title="Open Image",
@@ -64,17 +77,53 @@ def open_preview(event: Event):
     elif Path(file).exists() and Path(file).is_file():
         # load image data and resize to fit the IWII resolution preserving aspect ratio
         image_data = ImageOps.contain(Image.open(file), IWII_RESOLUTION)
-        photo = PhotoImage(image_data, size=IWII_RESOLUTION)
+
-        event.widget.create_image(0,0, anchor=NW, image=photo)
+        p_img = Image.new('P', image_data.size)
+        p_img.putpalette(IWII_PALETTE)
+
+        conv = image_data.quantize(palette=p_img).convert("RGB")
+
+        photo = PhotoImage(conv, size=IWII_RESOLUTION)
+        event.widget.create_image(0,0, anchor=CENTER, image=photo)
         # tkinter does not maintain a reference to the local variables of this function upon return
         # without references, the photo and its data get garbage collected and nothing is display
         # therefore we must create references to them to keep them around
         event.widget._displayed_photo=photo
-        event.widget.master.photobooth_image = image_data
+        event.widget.master.photobooth_image = conv
 
 @widget_action
-def send_to_iwii(event: Event):
+def send_to_printer(event: Event) -> None:
-    raise NotImplementedError        
+    if not event.widget.master.photobooth_image:
+        messagebox.showwarning(
+            title="Warning",
+            message="Nothing to print. Please take a picture first.",
+            parent=event.widget.master
+        )
+    else:
+        with Serial(
+            "/dev/ttyUSB0",
+            baudrate=9600,
+            xonxoff=True,
+            rtscts=False
+        ) as printer:
+            printer.write(event.widget.master.photobooth_image.tobytes())
+
+
+@widget_action
+def clear_preview(event: Event) -> None:
+    if event.widget.master.photobooth_image:
+        # remove the image data
+        event.widget.master.photobooth_image = None
+        # clear the canvas
+        event.widget.delete("all")
+        # remove the reference to the data formerly displayed on the canvas so it gets GC'd
+        del event.widget._displayed_photo
+
+
+@widget_action
+def quit_photobooth(event: Event) -> None:
+    event.widget.master.destroy()
+    event.widget.master.quit()
 
 
 def photobooth():
@@ -107,7 +156,9 @@ def photobooth():
 
     preview = Canvas(master=app, height=IWII_RESOLUTION.height, width=IWII_RESOLUTION.width)
     preview.bind("<space>", open_preview)
-    preview.bind("<Return>", send_to_iwii)
+    preview.bind("<Return>", send_to_printer)
+    preview.bind("c", clear_preview)
+    preview.bind("q", quit_photobooth)
     preview.focus_set()
     preview.pack(side="top")
     app.mainloop()