gh-anthropics-skills-example-skills/skills/slack-gif-creator/core/frame_composer.py

#!/usr/bin/env python3
"""
Frame Composer - Utilities for composing visual elements into frames.

Provides functions for drawing shapes, text, emojis, and compositing elements
together to create animation frames.
"""

from typing import Optional

import numpy as np
from PIL import Image, ImageDraw, ImageFont


def create_blank_frame(
    width: int, height: int, color: tuple[int, int, int] = (255, 255, 255)
) -> Image.Image:
    """
    Create a blank frame with solid color background.

    Args:
        width: Frame width
        height: Frame height
        color: RGB color tuple (default: white)

    Returns:
        PIL Image
    """
    return Image.new("RGB", (width, height), color)


def draw_circle(
    frame: Image.Image,
    center: tuple[int, int],
    radius: int,
    fill_color: Optional[tuple[int, int, int]] = None,
    outline_color: Optional[tuple[int, int, int]] = None,
    outline_width: int = 1,
) -> Image.Image:
    """
    Draw a circle on a frame.

    Args:
        frame: PIL Image to draw on
        center: (x, y) center position
        radius: Circle radius
        fill_color: RGB fill color (None for no fill)
        outline_color: RGB outline color (None for no outline)
        outline_width: Outline width in pixels

    Returns:
        Modified frame
    """
    draw = ImageDraw.Draw(frame)
    x, y = center
    bbox = [x - radius, y - radius, x + radius, y + radius]
    draw.ellipse(bbox, fill=fill_color, outline=outline_color, width=outline_width)
    return frame


def draw_text(
    frame: Image.Image,
    text: str,
    position: tuple[int, int],
    color: tuple[int, int, int] = (0, 0, 0),
    centered: bool = False,
) -> Image.Image:
    """
    Draw text on a frame.

    Args:
        frame: PIL Image to draw on
        text: Text to draw
        position: (x, y) position (top-left unless centered=True)
        color: RGB text color
        centered: If True, center text at position

    Returns:
        Modified frame
    """
    draw = ImageDraw.Draw(frame)

    # Uses Pillow's default font.
    # If the font should be changed for the emoji, add additional logic here.
    font = ImageFont.load_default()

    if centered:
        bbox = draw.textbbox((0, 0), text, font=font)
        text_width = bbox[2] - bbox[0]
        text_height = bbox[3] - bbox[1]
        x = position[0] - text_width // 2
        y = position[1] - text_height // 2
        position = (x, y)

    draw.text(position, text, fill=color, font=font)
    return frame


def create_gradient_background(
    width: int,
    height: int,
    top_color: tuple[int, int, int],
    bottom_color: tuple[int, int, int],
) -> Image.Image:
    """
    Create a vertical gradient background.

    Args:
        width: Frame width
        height: Frame height
        top_color: RGB color at top
        bottom_color: RGB color at bottom

    Returns:
        PIL Image with gradient
    """
    frame = Image.new("RGB", (width, height))
    draw = ImageDraw.Draw(frame)

    # Calculate color step for each row
    r1, g1, b1 = top_color
    r2, g2, b2 = bottom_color

    for y in range(height):
        # Interpolate color
        ratio = y / height
        r = int(r1 * (1 - ratio) + r2 * ratio)
        g = int(g1 * (1 - ratio) + g2 * ratio)
        b = int(b1 * (1 - ratio) + b2 * ratio)

        # Draw horizontal line
        draw.line([(0, y), (width, y)], fill=(r, g, b))

    return frame


def draw_star(
    frame: Image.Image,
    center: tuple[int, int],
    size: int,
    fill_color: tuple[int, int, int],
    outline_color: Optional[tuple[int, int, int]] = None,
    outline_width: int = 1,
) -> Image.Image:
    """
    Draw a 5-pointed star.

    Args:
        frame: PIL Image to draw on
        center: (x, y) center position
        size: Star size (outer radius)
        fill_color: RGB fill color
        outline_color: RGB outline color (None for no outline)
        outline_width: Outline width

    Returns:
        Modified frame
    """
    import math

    draw = ImageDraw.Draw(frame)
    x, y = center

    # Calculate star points
    points = []
    for i in range(10):
        angle = (i * 36 - 90) * math.pi / 180  # 36 degrees per point, start at top
        radius = size if i % 2 == 0 else size * 0.4  # Alternate between outer and inner
        px = x + radius * math.cos(angle)
        py = y + radius * math.sin(angle)
        points.append((px, py))

    # Draw star
    draw.polygon(points, fill=fill_color, outline=outline_color, width=outline_width)

    return frame