【x86/x64 only】Python と OpenCV と Pillow-SIMD でできる限り高速に外部フォントを使用した日本語文字列を指定文字幅で改行しながらレンダリングする

import cv2
import time
import numpy as np
np.random.seed(39)
from PIL import Image, ImageDraw, ImageFont
from collections import defaultdict
from typing import List, Dict, Tuple

def draw_text(
    images: List[np.ndarray],
    texts: List[List[str]],
    x: int,
    y: int,
    font_size: int,
    wrap_width: int,
    font: ImageFont.FreeTypeFont="./NotoSansCJK-Bold.ttc",
) -> List[np.ndarray]:
    """Function to draw text using Pillow, wrapping it to fit the specified width

    Parameters
    ----------
    images: List[np.ndarray]
        Images to draw a string.

    texts: List[List[str]]
        Strings to be drawn.

    x: int
        Drawing start coordinate X.

    y: int
        Drawing start coordinate Y.

    font_size: int
        Font size.

    wrap_width: int
        Width of the base on which to wrap the string.

    font: ImageFont.FreeTypeFont
        Font. Default: "./NotoSansCJK-Bold.ttc"

    Returns
    -------
    images_after_rendering: List[np.ndarray]
    """
    # Character width cache
    pil_images: List[Image.Image] = []
    draws: List[ImageDraw.ImageDraw] = []
    pane_line_char_widths: List[Dict] = []
    line_height = 0

    start_time = time.perf_counter()
    for image, lines in zip(images, texts):
        start_time1 = time.perf_counter()
        pil_image = Image.fromarray(image)
        draw = ImageDraw.Draw(pil_image)
        print(f'  1-1. {(time.perf_counter()-start_time1)*1000} ms')

        start_time2 = time.perf_counter()
        line_char_widths: List[Dict] = []
        for line in lines:
            line_char_widths.append({char: font_size for char in set(line)})
        if line_height ==0:
            line_height = draw.textbbox((0, 0), 'A', font=font)[3]

        pil_images.append(pil_image)
        draws.append(draw)
        pane_line_char_widths.append(line_char_widths)
        print(f'  1-2. {(time.perf_counter()-start_time2)*1000} ms')
    print(f'1. {(time.perf_counter()-start_time)*1000} ms')

    start_time = time.perf_counter()
    images_after_rendering: List[np.ndarray] = []

    for pil_image, draw, text, line_char_widths in \
        zip(pil_images, draws, texts, pane_line_char_widths):

        y0 = y
        lines: List[str] = []
        for line, char_widths in zip(text, line_char_widths):
            start_time1 = time.perf_counter()
            current_line: str = ''
            current_width: int = 0
            for char in list(line):
                if char == '\n' or current_width + char_widths[char] > wrap_width:
                    lines.append(current_line)
                    current_line = char
                    current_width = char_widths[char]
                else:
                    current_line += char
                    current_width += char_widths[char]
            lines.append(F'{current_line}\n')
        print(f'  2-1. {(time.perf_counter()-start_time1)*1000} ms')

        start_time2 = time.perf_counter()
        for line in lines:
            draw.text((x, y0), line, font=font, fill=(255, 255, 255))
            y0 += line_height + 5  # Leave 5 pixels between lines
        print(f'  2-2. {(time.perf_counter()-start_time2)*1000} ms')

        images_after_rendering.append(np.asarray(pil_image))
    print(f'2. {(time.perf_counter()-start_time)*1000} ms')

    return images_after_rendering

def main():
    # Number of text display area panes
    text_pane_num = 2
    # fixed color scheme
    color_palette: List[Tuple] = [
        (40, 40, 40), # almost black
        (255, 51, 51), # blue
    ]
    # random auto color scheme
    if text_pane_num > len(color_palette):
        random_bgr_colors = \
            np.random.randint(
                0,
                256,
                size=(text_pane_num - len(color_palette), 3)
            )
        color_palette = \
            color_palette + \
                [tuple(random_bgr_color) for random_bgr_color in random_bgr_colors]

    texts: List[List[str]] = \
        [
            [
                "１行目：これはテストです。abcde文字列が長い場合、ここで折り返しが行われます。",
                "２行目：２行目がただしく改行されて表示されることを確認します。",
            ],
            [
                "１行目：２つ目のペイン用",
                "２行目：テストテストテストテストテストテストテストテストテストテストテスト",
            ],
        ]
    font_path: str = "./NotoSansCJK-Bold.ttc"
    font_size: int = 20
    font: ImageFont.FreeTypeFont = \
        ImageFont.truetype(font=font_path, size=font_size)


    # Init Camera
    cap = cv2.VideoCapture(0)

    while True:
        ret, frame = cap.read()
        if not ret:
            break

        start_time = time.perf_counter()

        height, width, _ = frame.shape

        # Video Pane Size
        video_pane_height = height
        video_pane_width = width // 2

        # Text display pane size
        text_pane_width = 320
        text_pane_height = height // text_pane_num

        # Create base image for text display pane
        text_panes: List[np.ndarray] = \
            [
                np.full(
                    shape=(text_pane_height, text_pane_width, 3),
                    fill_value=color,
                    dtype=np.uint8,
                ) for color in color_palette
            ]

        # Draw strings in the display pane
        text_panes = \
            draw_text(
                images=text_panes,
                texts=texts,
                x=10,
                y=30,
                font_size=font_size,
                wrap_width=text_pane_width - font_size,
                font=font,
            )

        # Combine video pane and text display pane
        text_area = np.vstack(tuple(text_panes))
        combined = np.hstack((frame, text_area))

        end_time = (time.perf_counter() - start_time) * 1000
        cv2.putText(
            combined,
            f'{end_time:.2f} ms',
            (10, 30),
            cv2.FONT_HERSHEY_SIMPLEX,
            0.7,
            (255, 255, 255),
            2,
            cv2.LINE_AA,
        )
        cv2.putText(
            combined,
            f'{end_time:.2f} ms',
            (10, 30),
            cv2.FONT_HERSHEY_SIMPLEX,
            0.7,
            (0,0,255),
            1,
            cv2.LINE_AA,
        )

        cv2.imshow(winname='Video with Text', mat=combined)

        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

    if cap is not None:
        cap.release()
    cv2.destroyAllWindows()

if __name__ == "__main__":
    main()