--- title: "How to add a letter-by-letter reveal with Claude (tested prompt and script)" description: "\"GLOW IN 7 DAYS\" builds left to right along the bottom, each dark letter fading up from slightly below a beat after the one before it. Install one skill and ask Claude Code, or run the Python script we tested yourself." url: https://www.recharm.com/effects/letter-stagger-reveal --- # How to add a letter-by-letter reveal with Claude "GLOW IN 7 DAYS" builds left to right along the bottom, each dark letter fading up from slightly below a beat after the one before it. Made by the script on this page, from our own test clip. ## Get this effect 1. ### Switch to Code in your [Claude Desktop App](https://claude.com/download) 2. ### Install the skill (once) ``` Install the Recharm video effects skill: download https://recharm-growth-staging.s3.us-east-2.amazonaws.com/website/downloads/recharm-video-effects.zip and unzip it into ~/.claude/skills ``` 3. ### Ask for the effect ``` Add a letter-by-letter reveal to input.mp4 Text: GLOW IN 7 DAYS ``` ## Several videos, several effects, one ask Put your clips in the folder, mention them with @, and ask for everything at once. Claude runs one tested script after another on each clip, then joins them. Add a letter-by-letter reveal to **@clip1.mp4**, put a sale badge on **@clip2.mp4**, give **@clip3.mp4** a VHS look, then join all three with crossfades. ## Settings you can change Ask Claude to change any of these, or edit them at the top of the script. | Setting | Default | What it does | | --------- | ---------------- | --------------------------------------------------------- | | `TEXT` | `GLOW IN 7 DAYS` | The headline. | | `START` | `0.5` | Second the first letter starts to appear. | | `STAGGER` | `0.08` | Seconds between one letter starting and the next. | | `EASE_IN` | `0.45` | Seconds each letter takes to fade in and rise. | | `RISE` | `0.06` | How far each letter rises, as a share of the frame width. | | `SIZE` | `0.09` | Text height as a share of the frame width. | | `Y` | `0.86` | Where the line's center sits (0 = top, 1 = bottom). | | `COLOR` | `(25, 15, 50)` | Text color. | ## Without the skill Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the script itself. ``` Add a letter-by-letter reveal to input.mp4: the line "GLOW IN 7 DAYS" in Arial Black (or any heavy bold font) 9% of the frame width tall, deep ink color (25, 15, 50), centered across with its center 86% of the way down. Each letter (spaces included in the count) starts 0.08 seconds after the one before, the first at 0.5 seconds. Over 0.45 seconds with a cubic ease-out, each letter fades from fully transparent to solid while rising 6% of the frame width into its final place; then every letter stays to the end. Nothing shows before 0.5 seconds. 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. ``` ## Run it without Claude This is the exact script we tested. Save it as `letter-stagger-reveal.py` and run: ``` python3 letter-stagger-reveal.py input.mp4 output.mp4 ``` ``` #!/usr/bin/env python3 """Letter-by-letter reveal: each letter of a headline fades in and rises into place a moment after the one before. Usage: python3 letter-stagger-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 TEXT = "GLOW IN 7 DAYS" # the headline START = 0.5 # second the first letter starts to appear STAGGER = 0.08 # seconds between one letter starting and the next EASE_IN = 0.45 # seconds each letter takes to fade in and rise RISE = 0.06 # how far each letter rises, as a share of the frame width SIZE = 0.09 # text height as a share of the frame width Y = 0.86 # where the 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 letter_tiles(): """Each letter drawn once on its own tile, plus the x where its tile goes.""" font = ImageFont.truetype(FONT_FILE, round(w * SIZE)) pad = round(w * SIZE * 0.2) left = (w - font.getlength(TEXT)) / 2 tiles = [] for i, ch in enumerate(TEXT): if ch == " ": continue size = (round(font.getlength(ch)) + 2 * pad, round(w * SIZE * 1.4) + 2 * pad) tile = Image.new("RGBA", size) ImageDraw.Draw(tile).text((pad, size[1] / 2), ch, font=font, anchor="lm", fill=COLOR) tiles.append((i, tile, round(left + font.getlength(TEXT[:i]) - pad))) return tiles def overlay(t): """Letter i starts at START + i * STAGGER, fading from clear to solid while rising RISE into place.""" img = Image.new("RGBA", (w, h)) for i, tile, x in tiles: p = ease_out((t - START - i * STAGGER) / EASE_IN) if p <= 0: continue faded = tile.copy() faded.putalpha(tile.getchannel("A").point(lambda a: round(a * p))) y = round(h * Y - tile.height / 2 + (1 - p) * w * RISE) img.alpha_composite(faded, (x, y)) return img def ease_out(p): """0 -> 1, fast at first and settling softly (cubic ease-out).""" p = min(max(p, 0), 1) return 1 - (1 - p) ** 3 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) tiles = letter_tiles() render(src, out) ``` ## More captions and text - [AI chat reply animation **AI chat reply animation**](https://www.recharm.com/effects/ai-chat-typing) - [Animated bar chart **Animated bar chart**](https://www.recharm.com/effects/animated-bar-chart) - [Animated checklist **Animated checklist**](https://www.recharm.com/effects/animated-checklist) - [Animated line graph **Animated line graph**](https://www.recharm.com/effects/animated-line-graph) - [Animated pie chart **Animated pie chart**](https://www.recharm.com/effects/animated-pie-chart) ## Find 3x _winning ads_ Recharm cuts your ad footage into tagged, searchable clips: hooks, testimonials, product shots. Find the shots that win, add the effect with Claude, and ship 3x more ad edits. [Start 14-day free trial](https://www.recharm.com/get-started)