How to add a masked text reveal with Claude

Add a masked text reveal to input.mp4: a two-line headline, "GLOW STARTS" over "HERE", in Arial Black (or any heavy bold font) 9% of the frame width tall, deep ink color (25, 15, 50), centered across. Give each line its own invisible window 1.25 times the font size tall and the full frame width: the first window is centered 9% of the way down, the second sits directly under it. Each line starts just below the bottom edge of its window, hidden, and slides straight up into place over 0.5 seconds with an ease-out (fast start, soft landing); anything below the window's bottom edge is cut off, so the text appears to rise from behind an edge. The first line starts at 0.5 seconds, the second 0.3 seconds later, and both then stay to the end. Use Python with Pillow to draw the text and ffmpeg to put it on the video (don't rely on ffmpeg's drawtext filter), keep the audio, and save it as output.mp4.

#!/usr/bin/env python3
"""Masked text reveal: each line of a headline slides up into view from behind an invisible edge.

Usage: python3 masked-text-reveal.py input.mp4 output.mp4
Needs ffmpeg and Pillow (pip install pillow).
"""
import json
import math
import subprocess
import sys
from pathlib import Path

from PIL import Image, ImageDraw, ImageFont

LINES = ["GLOW STARTS", "HERE"]  # headline, one entry per line
START = 0.5              # second the first line starts to rise
STAGGER = 0.3            # seconds between one line starting and the next
RISE = 0.5               # seconds each line takes to slide up
SIZE = 0.09              # text height as a share of the frame width
Y = 0.09                 # where the first line's center sits (0 = top, 1 = bottom)
COLOR = (25, 15, 50)     # text color, a deep ink
FONTS = ["/System/Library/Fonts/Supplemental/Arial Black.ttf",    # macOS
         "/System/Library/Fonts/Supplemental/Arial Bold.ttf",     # macOS
         "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf",  # Linux
         "C:/Windows/Fonts/ariblk.ttf"]                           # Windows
FONT_FILE = next((f for f in FONTS if Path(f).exists()), None) or sys.exit("No bold font found: add one to FONTS")


def line_strip(text, font, height):
    """One line drawn once, centered in a full-width strip."""
    img = Image.new("RGBA", (w, height))
    ImageDraw.Draw(img).text((w / 2, height / 2), text, font=font, anchor="mm", fill=COLOR)
    return img


def overlay(t):
    """Each line sits in its own window; until it rises, it waits just below the window's bottom edge, out of sight."""
    img = Image.new("RGBA", (w, h))
    for i, strip in enumerate(strips):
        p = min(max((t - START - i * STAGGER) / RISE, 0), 1)
        if p == 0:
            continue
        drop = round((1 - p) ** 3 * strip.height)  # how far below its window the line still is; ease out
        top = round(h * Y + i * strip.height - strip.height / 2)
        img.alpha_composite(strip.crop((0, 0, w, strip.height - drop)), (0, top + drop))
    return img


def probe(path):
    info = json.loads(subprocess.check_output(["ffprobe", "-v", "error", "-select_streams", "v:0", "-show_entries",
                                               "stream=width,height,r_frame_rate:format=duration", "-of", "json", path]))
    s = info["streams"][0]
    num, den = s["r_frame_rate"].split("/")
    return s["width"], s["height"], s["r_frame_rate"], float(num) / float(den), float(info["format"]["duration"])


def render(src, out):
    """Draw overlay(t) on every frame of src and save to out, keeping the audio."""
    ff = subprocess.Popen(["ffmpeg", "-y", "-v", "error", "-i", src,
                           "-f", "rawvideo", "-pix_fmt", "rgba", "-s", f"{w}x{h}", "-r", rate, "-i", "-",
                           "-filter_complex", "[0:v][1:v]overlay=shortest=1,format=yuv420p[v]",
                           "-map", "[v]", "-map", "0:a?", "-c:v", "libx264", "-crf", "18", "-c:a", "copy", out],
                          stdin=subprocess.PIPE)
    for i in range(math.ceil(duration * fps)):
        ff.stdin.write(overlay(i / fps).tobytes())
    ff.stdin.close()
    if ff.wait():
        sys.exit("ffmpeg failed")


src, out = sys.argv[1:3]
w, h, rate, fps, duration = probe(src)
font = ImageFont.truetype(FONT_FILE, round(w * SIZE))
strips = [line_strip(line, font, round(font.size * 1.25)) for line in LINES]
render(src, out)