Initial code

cover.py

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+import textwrap
+import urllib
+import urllib.parse
+import urllib.request
+from io import BytesIO
+
+import click
+from PIL import Image, ImageColor, ImageDraw, ImageFont
+
+
+def _map(value, istart, istop, ostart, ostop):
+    """
+    Helper function that implements the Processing function map(). For more
+    details see https://processing.org/reference/map_.html
+    http://stackoverflow.com/questions/17134839/how-does-the-map-function-in-processing-work
+    """
+    return ostart + (ostop - ostart) * ((value - istart) / (istop - istart))
+
+
+def _clip(value, lower, upper):
+    """
+    Helper function to clip a given value based on a lower/upper bound.
+    """
+    return lower if value < lower else upper if value > upper else value
+
+
+cover_width = 1200
+cover_height = 1800
+
+
+@click.command()
+@click.option("-t", "--title", metavar="<title>", help="Book title")
+@click.option(
+    "-s", "--subtitle", metavar="<subtitle>", help="Book subtitle", default=None
+)
+@click.option("-a", "--author", metavar="<author>", help="Book author", default=None)
+@click.option("-o", "--output", metavar="<filename>", help="Output file (- for stdout)")
+def cover(title, author, output, subtitle):
+    def processColors():
+        base_saturation = 100
+        base_brightness = 90
+        color_distance = 100
+        invert = True
+
+        counts = len(title) + len(author)
+        color_seed = int(_map(_clip(counts, 2, 80), 2, 80, 10, 360))
+        shape_color = ImageColor.getrgb(
+            f"hsv({color_seed}, {base_saturation}%, {base_brightness - (counts % 20)}%)"
+        )
+        base_color = ImageColor.getrgb(
+            f"hsv({(color_seed + color_distance) % 360}, {base_saturation}%, {base_brightness}%)"
+        )
+        if invert:
+            shape_color, base_color = base_color, shape_color
+        if (counts % 10) == 0:
+            shape_color, base_color = base_color, shape_color
+        return shape_color, base_color
+
+    # Fill the background of the image with white.
+    def drawBackground():
+        fill = ImageColor.getrgb("#fff")
+        image_draw.rectangle((0, 0, cover_width, cover_height), fill=fill)
+
+    # Allocate fonts for the title and the author, and draw the text.
+    def drawText():
+        fill = ImageColor.getrgb("rgb(50, 50, 50)")
+
+        title_font_size = int(cover_width * 0.08)
+        subtitle_font_size = int(cover_width * 0.05)
+        author_font_size = int(cover_width * 0.06)
+        title_font = ImageFont.truetype(
+            "/usr/share/fonts/TTF/Hack-Regular.ttf", title_font_size
+        )
+        subtitle_font = ImageFont.truetype(
+            "/usr/share/fonts/TTF/Hack-Regular.ttf", subtitle_font_size
+        )
+        author_font = ImageFont.truetype(
+            "/usr/share/fonts/TTF/Hack-Regular.ttf", author_font_size
+        )
+
+        title_height = (
+            cover_height - cover_width - (cover_height * cover_margin / 100)
+        ) * 0.6
+
+        x = cover_height * cover_margin / 100
+        y = cover_height * cover_margin / 100 * 2
+        wrapped = textwrap.wrap(title, 18)
+        image_draw.text((x, y), "\n".join(wrapped), font=title_font, fill=fill)
+
+        bbox = image_draw.textbbox((x, y), "\n".join(wrapped), font=title_font)
+        title_height = bbox[3] - bbox[1]
+        y = y + title_height + 0.03 * cover_height
+
+        if subtitle:
+            image_draw.text(
+                (x, y),
+                "\n".join(textwrap.wrap(subtitle)),
+                font=subtitle_font,
+                fill=fill,
+            )
+
+            bbox = image_draw.textbbox((x, y), "\n".join(wrapped), font=title_font)
+            subtitle_height = bbox[3] - bbox[1]
+            y = y + subtitle_height + 0.03 * cover_height
+
+        x = cover_height * cover_margin / 100
+        image_draw.text((x, y), author, font=author_font, fill=fill)
+
+    def drawArtwork():
+        artwork_start_x = 0
+        artwork_start_y = cover_height - cover_width
+
+        with urllib.request.urlopen(
+            f"https://api.dicebear.com/6.x/identicon/png?seed={urllib.parse.quote(title)}&size={cover_width}"
+        ) as request:
+            art = Image.open(BytesIO(request.read())).resize((cover_width, cover_width))
+
+        cover_image.paste(art, (artwork_start_x, artwork_start_y))
+
+    # Create the new cover image.
+    cover_margin = 2
+    cover_image = Image.new("RGB", (cover_width, cover_height))
+    image_draw = ImageDraw.Draw(cover_image)
+
+    # Draw the book cover.
+    shape_color, base_color = processColors()
+    drawBackground()
+    drawArtwork()
+    drawText()
+
+    # Return the cover Image instance.
+    cover_image.save(output)
+
+
+if __name__ == "__main__":
+    cover()

requirements.txt

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+pillow
+click