Merge pull request #334 from mathoudebine/fix/289-high-rate-of-access…

…ing-a-background-file

library/lcd/lcd_comm.py

@@ -16,6 +16,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+import copy
 import os
 import queue
 import sys
@@ -62,6 +63,13 @@ def __init__(self, com_port: str = "AUTO", display_width: int = 320, display_hei
         # mixed with other requests in-between
         self.update_queue_mutex = threading.Lock()
 
+        # Create a cache to store opened images, to avoid opening and loading from the filesystem every time
+        self.image_cache = {}  # { key=path, value=PIL.Image }
+
+        # Create a cache to store opened fonts, to avoid opening and loading from the filesystem every time
+        self.font_cache = {}  # { key=(font, size), value=PIL.ImageFont }
+
+
     def get_width(self) -> int:
         if self.orientation == Orientation.PORTRAIT or self.orientation == Orientation.REVERSE_PORTRAIT:
             return self.display_width
@@ -194,7 +202,7 @@ def DisplayPILImage(
         pass
 
     def DisplayBitmap(self, bitmap_path: str, x: int = 0, y: int = 0, width: int = 0, height: int = 0):
-        image = Image.open(bitmap_path)
+        image = self.open_image(bitmap_path)
         self.DisplayPILImage(image, x, y, width, height)
 
     def DisplayText(
@@ -235,10 +243,12 @@ def DisplayText(
             )
         else:
             # The text bitmap is created from provided background image : text with transparent background
-            text_image = Image.open(background_image)
+            text_image = self.open_image(background_image)
 
         # Get text bounding box
-        font = ImageFont.truetype("./res/fonts/" + font, font_size)
+        if (font, font_size) not in self.font_cache:
+            self.font_cache[(font, font_size)] = ImageFont.truetype("./res/fonts/" + font, font_size)
+        font = self.font_cache[(font, font_size)]
         d = ImageDraw.Draw(text_image)
         left, top, right, bottom = d.textbbox((x, y), text, font=font, align=align, anchor=anchor)
 
@@ -294,7 +304,7 @@ def DisplayProgressBar(self, x: int, y: int, width: int, height: int, min_value:
             bar_image = Image.new('RGB', (width, height), background_color)
         else:
             # A bitmap is created from provided background image
-            bar_image = Image.open(background_image)
+            bar_image = self.open_image(background_image)
 
             # Crop bitmap to keep only the progress bar background
             bar_image = bar_image.crop(box=(x, y, x + width, y + height))
@@ -372,7 +382,7 @@ def DisplayRadialProgressBar(self, xc: int, yc: int, radius: int, bar_width: int
             bar_image = Image.new('RGB', (diameter, diameter), background_color)
         else:
             # A bitmap is created from provided background image
-            bar_image = Image.open(background_image)
+            bar_image = self.open_image(background_image)
 
             # Crop bitmap to keep only the progress bar background
             bar_image = bar_image.crop(box=bbox)
@@ -464,3 +474,10 @@ def DisplayRadialProgressBar(self, xc: int, yc: int, radius: int, bar_width: int
                       font=font, fill=font_color)
 
         self.DisplayPILImage(bar_image, xc - radius, yc - radius)
+
+    # Load image from the filesystem, or get from the cache if it has already been loaded previously
+    def open_image(self, bitmap_path: str) -> Image:
+        if bitmap_path not in self.image_cache:
+            logger.debug("Bitmap " + bitmap_path + " is now loaded in the cache")
+            self.image_cache[bitmap_path] = Image.open(bitmap_path)
+        return copy.copy(self.image_cache[bitmap_path])