Simple class for writing multiline textcentered on a PIL image with even linespacing.

pil_line_writer.py

"""
PIL Line Writer

Simple class for writing multiline text centered on an image with even line
spacing.

To use create a line writer object by passing a PIL image object and a padding
value. Then to write text call the LineWriter's text method with the text you
would like centered on the image over multiple lines. It also takes an optional
line height argument which will scale the line heights. Additionally you can
pass any keyword settings that are valid for ImageDraw.draw.text.

Example:
    image = Image.new("RGBA", (300, 300), "yellow")
    writer = LineWriter(image, 60)
    writer.text(
        "To the inspiration of necessity, we owe half the wise, beautiful, and useful blessings of the world.",
        1.5,
        fill="black"
    )
    image.show()
"""
from PIL import Image, ImageDraw


class LineWriter:
    """ Simple class for writing multiline text centered on a PIL image with
    even line spacing. """
    def __init__(self, image: Image.Image, padding: int, offset_x: int = 0, offset_y: int = 0):
        self._image = image
        self._draw = ImageDraw.Draw(image)
        self._padding = padding
        self._last_line_y = 0
        self._offset_x = offset_x
        self._offset_y = offset_y

    @property
    def height(self) -> int:
        """ Height of the image. """
        return self._image.size[1]

    @property
    def last_line_y(self) -> int:
        """ Gives the y position after the last line drawn. """
        return self._last_line_y

    @property
    def width(self) -> int:
        """ Width of the image. """
        return self._image.size[0]

    def line_height(self, font) -> int:
        """ Height of our standard line. """
        return self._draw.textsize("hj", font=font)[0]

    def text(self, message: str, line_height: float=1.0, **settings):
        """ Writes the text centered on the image. Takes a line height argument
        for scaling the line height and also takes all valid keywords for
        ImageDraw.Draw.text. """
        lines = self._build_lines(message, settings.get("font"))
        height = self.line_height(settings.get("font")) * line_height
        self._last_line_y = (self.height - len(lines) * height) // 2
        for line in lines:
            width, _ = self._draw.textsize(line, settings.get("font"))
            self._draw.text(
                (
                    (self.width - width) // 2 + self._offset_x,
                    self.last_line_y + self._offset_y
                ),
                line,
                **settings
            )
            self._last_line_y += height

    def _build_lines(self, message: str, font):
        """ Breaks a line of text up into a series of lines that fit onto the
        image with the correct padding. """
        lines = []
        line = []
        for word in message.split(" "):
            test_line = list(line)
            test_line.append(word)
            width, _ = self._draw.textsize(" ".join(test_line), font=font)
            if width > self.width - self._padding * 2:
                lines.append(" ".join(line))
                line = [word]
            else:
                line = test_line
        if line:
            lines.append(" ".join(line))
        return lines


if __name__ == "__main__":
     image = Image.new("RGBA", (300, 300), "yellow")
     writer = LineWriter(image, 60)
     writer.text(
         "To the inspiration of necessity, we owe half the wise, beautiful, and useful blessings of the world.",
         1.5,
         fill="black"
     )
     image.show()