improve font size calculation algorithm

src/cogs/meme.py

@@ -70,39 +70,7 @@ class Meme(commands.Cog):
         await interaction.followup.send(file=discord.File(output, "deepfry.jpg"))
 
     @staticmethod
-    def __format_text(text: str, textbox_width: int) -> tuple[str, ImageFont.FreeTypeFont]:
-        """
-        Formats text to fit in a textbox of a given width.
-
-        Parameters
-        ----------
-        text (str): Text to be formatted.
-        textbox_width (int): Width of the textbox.
-
-        Returns
-        ----------
-        tuple[str, ImageFont.FreeTypeFont]: The formatted text and the font, with its size set, to be used.
-        """
-
-        if len(text) <= 1:
-            font_size = 150
-        else:
-            font_size = textbox_width // (len(text) // 6)
-
-        if font_size < 20:
-            font_size = 20
-        elif font_size > 150:
-            font_size = 150
-
-        font = ImageFont.truetype("./src/assets/fonts/RobotoMono-Medium.ttf", font_size)
-
-        line_length = int(textbox_width // font_size * 1.5)
-        text = textwrap.fill(text, width=line_length)
-
-        return text, font
-
-    @staticmethod
-    def __draw_text(image: Image.Image, text: str, font: ImageFont.FreeTypeFont, offset: tuple = (0, 0)):
+    def __draw_text(image: Image.Image, text: str, offset: tuple = (0, 0)):
         """
         Draws meme text on preferred meme template.
 
@@ -115,13 +83,59 @@ class Meme(commands.Cog):
         """
 
         box_size = (540, 540)
-
         box = Image.new("RGB", box_size, (255, 255, 255))
         draw = ImageDraw.Draw(box)
 
-        text_box = draw.multiline_textbbox(
-            (box_size[0], box_size[1]), text=text, font=font, align="center", anchor="mm"
-        )
+        font_path = "./src/assets/fonts/RobotoMono-Medium.ttf"
+
+        # Calculate initial font size
+        # This is done by increasing the font size until the text is too wide
+        max_width, max_height = box_size[0] * 0.9, box_size[1] * 0.9  # 90% of the box size
+
+        font_size = 20  # Initiale size. I consider this the smallest readable size
+        font_width = 0  # Initiale width. This is just to make sure the while loop runs at least once
+        while font_width < max_width:
+            font = ImageFont.truetype(font_path, font_size)
+
+            font_box = font.getbbox(text)
+            font_width = font_box[2] - font_box[0]
+
+            font_size += 2
+
+        # Wrap the text based on our current font size
+        text = textwrap.fill(text, width=font_size)
+
+        # We then have to calculate the font size again
+        #
+        # The problem is, font.getbbox() doesn't work with multiline text so it returns the size without the linebreaks
+        # We can get around this by calculating the size of the longest line in the text
+        # and then increasing the font size until that line is too wide
+        #
+        # We also have to make sure it doesn't get too tall
+        longest_line = max(text.split("\n"), key=len)
+        longest_line_font_box = font.getbbox(longest_line)
+        font_width = longest_line_font_box[2] - longest_line_font_box[0]
+
+        # Estimate font height
+        # This is done by multiplying the height of the original non-wrapped text with the number of lines
+        # and then adding 20 to account for the line spacing.
+        # This of course is dependant on font size itself, but it's good enough for now
+        font_height = (font_box[3] - font_box[1] + 20) * text.count("\n")
+        max_height = box_size[1] * 0.9
+
+        while font_width < max_width and font_height < max_height:
+            font = ImageFont.truetype(font_path, font_size)
+
+            longest_line_font_box = font.getbbox(longest_line)
+            font_width = longest_line_font_box[2] - longest_line_font_box[0]
+
+            font_box = font.getbbox(text)
+            font_height = (font_box[3] - font_box[1] + 20) * text.count("\n")
+
+            font_size += 2
+
+        # Draw textbox and text
+        text_box = draw.multiline_textbbox(box_size, text=text, font=font, align="center", anchor="mm")
         text_box = box.size[0] // 2, box.size[1] // 2
         draw.multiline_text(text_box, text, font=font, fill=(0, 0, 0, 255), align="center", anchor="mm")
 
@@ -146,13 +160,9 @@ class Meme(commands.Cog):
         # Fetch meme template
         template = Image.open("./src/assets/misc/sivert_goodbad.jpg")
 
-        # Calculate font sizes
-        top_text, top_font = Meme.__format_text(dårlig_tekst, 540)
-        bottom_text, bottom_font = Meme.__format_text(bra_tekst, 540)
-
         # Draw text
-        Meme.__draw_text(template, top_text, top_font, offset=(540, 0))
-        Meme.__draw_text(template, bottom_text, bottom_font, offset=(540, 540))
+        Meme.__draw_text(template, dårlig_tekst, offset=(540, 0))
+        Meme.__draw_text(template, bra_tekst, offset=(540, 540))
 
         # Save image to buffer
         output = BytesIO()