--- title: "How to add a shaking text with Claude (tested prompt and script)" description: "\"BACK IN STOCK!\" appears in bold yellow near the top and every letter jolts and twists on its own each frame, while the shot behind stays steady. Install one skill and ask Claude Code, or run the Python script we tested yourself." url: https://www.recharm.com/effects/shaking-text --- # How to add a shaking text with Claude "BACK IN STOCK!" appears in bold yellow near the top and every letter jolts and twists on its own each frame, while the shot behind stays steady. 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 shaking text to input.mp4 Lines: ["BACK IN", "STOCK!"] ``` ## 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 shaking text 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 | | --------- | ----------------------- | -------------------------------------------------------------------- | | `LINES` | `["BACK IN", "STOCK!"]` | The text, one entry per line. | | `START` | `0.5` | Second the text appears. | | `Y` | `0.17` | Center of the text block (0 = top, 1 = bottom). | | `WIDTH` | `0.8` | The longest line's width as a share of the frame width. | | `COLOR` | `(255, 214, 0)` | Text color. | | `OUTLINE` | `0.012` | Black outline thickness as a share of the frame width. | | `JITTER` | `0.012` | How far a letter can jump each frame, as a share of the frame width. | | `TILT` | `6` | How far a letter can twist each frame, in degrees. | | `SEED` | `7` | Change for a different (but repeatable) shake. | ## Without the skill Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the script itself. ``` Add shaking text to input.mp4: "BACK IN" over "STOCK!" in a heavy bold font (Arial Black), yellow (255, 214, 0) with a black outline 1.2% of the frame width thick, the longer line 80% of the frame width wide, line spacing 1.1 times the font size, the two-line block centered horizontally and 17% of the way down. It appears at 0.5 seconds and stays to the end. On every frame, move each letter on its own by a random amount up to 1.2% of the frame width left or right and up or down from its place, and turn it by a random angle up to 6 degrees either way, so the letters jitter like a shout. Only the text shakes: the video behind stays untouched, and nothing changes before 0.5 seconds. Draw the text with Python and Pillow (don't rely on ffmpeg's drawtext filter), keep the size and audio, and save it as output.mp4. ``` ## Run it without Claude This is the exact script we tested. Save it as `shaking-text.py` and run: ``` python3 shaking-text.py input.mp4 output.mp4 ``` ``` #!/usr/bin/env python3 """Shaking text: a bold yellow shout appears and every letter jitters on its own, a few pixels each frame. Usage: python3 shaking-text.py input.mp4 output.mp4 Needs ffmpeg and Pillow (pip install pillow). """ import json import math import random import subprocess import sys from pathlib import Path from PIL import Image, ImageDraw, ImageFont LINES = ["BACK IN", "STOCK!"] # the text, one entry per line START = 0.5 # second the text appears Y = 0.17 # center of the text block (0 = top, 1 = bottom) WIDTH = 0.8 # the longest line's width as a share of the frame width COLOR = (255, 214, 0) # text color OUTLINE = 0.012 # black outline thickness as a share of the frame width JITTER = 0.012 # how far a letter can jump each frame, as a share of the frame width TILT = 6 # how far a letter can twist each frame, in degrees SEED = 7 # change for a different (but repeatable) shake FONTS = ["/System/Library/Fonts/Supplemental/Arial Black.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 layout(): """Each letter's picture and resting center, with the block sized so the longest line fills WIDTH.""" stroke = round(w * OUTLINE) longest = max(LINES, key=len) probe_font = ImageFont.truetype(FONT_FILE, 100) font = ImageFont.truetype(FONT_FILE, round(100 * w * WIDTH / probe_font.getlength(longest))) line_h = font.size * 1.1 top = h * Y - line_h * len(LINES) / 2 letters = [] for row, line in enumerate(LINES): x = (w - font.getlength(line)) / 2 cy = top + line_h * (row + 0.5) for ch in line: adv = font.getlength(ch) if ch != " ": pad = stroke + font.size // 4 img = Image.new("RGBA", (round(adv) + 2 * pad, font.size + 2 * pad)) ImageDraw.Draw(img).text((img.width / 2, img.height / 2), ch, font=font, anchor="mm", fill=COLOR, stroke_width=stroke, stroke_fill="black") letters.append((img, x + adv / 2, cy)) x += adv return letters def overlay(t): img = Image.new("RGBA", (w, h)) if t < START: return img rng = random.Random(f"{SEED}-{round(t * fps)}") # a fresh jolt for every letter on every frame reach = w * JITTER for pic, cx, cy in letters: turned = pic.rotate(rng.uniform(-TILT, TILT), resample=Image.BICUBIC) x = cx + rng.uniform(-reach, reach) y = cy + rng.uniform(-reach, reach) img.alpha_composite(turned, (round(x - turned.width / 2), round(y - turned.height / 2))) 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) letters = layout() 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)