Compress PNG and JPEG screenshots in place using pngquant and jpegoptim, keeping the original format for maximum compatibility.

Skill: Screenshot Compression Compress screenshot images (PNG/JPEG) in place while keeping the original format. Uses pngquant for PNG and jpegoptim for JPEG — both are highly effective for screenshot content (UI elements, text, flat colors). Prerequisites : pngquant and jpegoptim must be installed on the system. The script will not install them automatically — it checks for their presence and prints install instructions if missing. When to Use The user has screenshot files that are too large and wants to reduce file size without changing format. Common scenarios: Preparing images for GitHub READMEs, blog posts, or documentation Reducing image sizes before committing to a repository Batch compressing a directory of screenshots Why Keep Original Format (Not WebP) WebP has better compression, but poor compatibility in some contexts: Context WebP Support Browsers (Chrome/Firefox/Safari/Edge) Yes GitHub Issues/PRs Yes WeChat editor No Word / PowerPoint No Some forums/blog backends Varies Keeping PNG/JPEG ensures the compressed images work everywhere. Default Workflow The script will: 1. Check that pngquant and jpegoptim are installed — if not, print install instructions and exit 2. Auto detect file format by extension 3. Compress each file in place (overwrites the original) 4. Print per file and total compression summary Dependency Check The script requires two system tools. If either is missing, it exits with install instructions instead of proceeding. Do not install them on behalf of the user — just relay the error message so the user can install them. Install commands: Script Options Flag Default Description paths (positional) required Image files or directories to compress r , recursive off Recursively process directories png quality 80 95 pngquant quality range (min max, 0 100) jpeg quality 85 jpegoptim max quality (0 100) Examples Quality Tuning Guide Scenario png quality jpeg quality General screenshots (docs, web pages) 80 95 85 Code screenshots (need sharp text) 90 100 90 Thumbnails / previews (size priority) 60 80 70 How It Works PNG (pngquant) Quantizes 24 bit true color (16M colors) down to an 8 bit palette (256 colors) Uses Floyd Steinberg dithering for smooth gradients Screenshots are ideal candidates — UI colors are typically well under 256 unique values Typical reduction: 60 80% JPEG (jpegoptim) Re encodes at the specified quality level Strips metadata (EXIF, ICC profiles, thumbnails) via strip all Optimizes Huffman tables Typical reduction: 20 50% Important Notes Files are compressed in place — the original is overwritten. Back up files first if needed. Only .png , .jpg , and .jpeg files are processed. Other formats are silently skipped. The script never installs dependencies. If tools are missing, it prints install instructions and exits.

screenshot-compression