--- title: "How to add a text highlight marker with Claude (tested prompt and script)" description: "A yellow marker stroke swipes in behind the key words of the headline. Install one skill and ask Claude Code, or run the Python script we tested yourself." url: https://www.recharm.com/effects/text-highlight-marker --- # How to add a text highlight marker with Claude A yellow marker stroke swipes in behind the key words of the headline. 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 text highlight marker to input.mp4 Text: Clears dark spots Mark: dark spots ``` ## 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 text highlight marker 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` | `Clears dark spots` | The headline. | | `MARK` | `dark spots` | The words that get highlighted. | | `START` | `0.6` | Second the marker starts. | | `SWIPE` | `0.4` | Seconds the marker takes. | ## In other editors From each editor’s own help pages, in our words. We haven’t run these ourselves. Closest built-in: **Highlight** 1. Double-click the text, or click Edit at the top, to open the text panel. 2. Select the key words and click the highlight pop-up. 3. Change the highlight color with the Text color option. Page covers highlighting selected words with a color; no animated marker swipe is mentioned. Source: [How to highlight a text and change its color and font style? | Support](https://help-studio.invideo.io/en/articles/9404919-how-to-highlight-a-text-and-change-its-color-and-font-style) (InVideo), checked October 22, 2026. ## Without the skill Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the script itself. ``` Add a highlighted headline to input.mp4: "Clears dark spots" in black bold, centered 20% of the way down, and starting at 0.6 seconds a yellow marker rectangle swipes left to right behind "dark spots" over 0.4 seconds and stays. Use Python with Pillow to draw it 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 `text-highlight-marker.py` and run: ``` python3 text-highlight-marker.py input.mp4 output.mp4 ``` ``` #!/usr/bin/env python3 """Text highlight marker: a yellow marker stroke swipes in behind the key words of a headline. Usage: python3 text-highlight-marker.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 = "Clears dark spots" MARK = "dark spots" # the words that get highlighted (must be part of TEXT) START = 0.6 # second the marker starts SWIPE = 0.4 # seconds the marker takes to cross the words SIZE = 0.09 # text height as a share of the frame width Y = 0.20 # where the text's center sits (0 = top, 1 = bottom) MARKER = (255, 214, 0, 235) # marker color (last number is opacity, 0-255) FONTS = ["/System/Library/Fonts/Supplemental/Arial Bold.ttf", # macOS "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf", # Linux "C:/Windows/Fonts/arialbd.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 overlay(t): img = Image.new("RGBA", (w, h)) draw = ImageDraw.Draw(img) x0, y0, x1, y1 = draw.textbbox((w / 2, h * Y), TEXT, font=font, anchor="mm") start = x0 + font.getlength(TEXT[:TEXT.index(MARK)]) end = start + font.getlength(MARK) if t >= START: p = min(1, (t - START) / SWIPE) pad = font.size * 0.12 draw.rectangle([start - pad, y0 - pad, start - pad + (end - start + 2 * pad) * p, y1 + pad], fill=MARKER) draw.text((w / 2, h * Y), TEXT, font=font, anchor="mm", fill="black") 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)) 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)