#!/bin/bash
set -euo pipefail
# Script to convert PNG frame sequences to animated WebP using img2webp
# Handles large numbers of frames by using argument file approach
usage() {
cat << EOF
Usage: $0 <input_pattern> <output_file>
Examples:
$0 "~/screenshots/frame_*.png" output.webp
$0 "/path/to/frames/*.png" animation.webp
$0 "./frame_*.png" result.webp
The script will:
- Find all matching PNG files
- Sort them naturally (frame_1, frame_2, ... frame_10, frame_11, ...)
- Create lossless animated WebP at 10fps with maximum compression
- Optimize for screenshot content with temporal compression (kmin=10, kmax=100)
Requirements:
- img2webp must be installed (from webp/libwebp-tools package)
EOF
exit 1
}
# Check arguments
if [ $# -ne 2 ]; then
echo "Error: Wrong number of arguments"
echo
usage
fi
INPUT_PATTERN="$1"
OUTPUT_FILE="$2"
# Check if img2webp is available
if ! command -v img2webp &> /dev/null; then
echo "Error: img2webp not found. Please install it:"
echo " Ubuntu/Debian: sudo apt install webp"
echo " Fedora: sudo dnf install libwebp-tools"
echo " Arch: sudo pacman -S libwebp"
exit 1
fi
# Expand tilde and get directory and pattern
INPUT_PATTERN="${INPUT_PATTERN/#\~/$HOME}"
DIRECTORY="$(dirname "$INPUT_PATTERN")"
PATTERN="$(basename "$INPUT_PATTERN")"
# Check if directory exists
if [ ! -d "$DIRECTORY" ]; then
echo "Error: Directory does not exist: $DIRECTORY"
exit 1
fi
# Create temporary argument file
TEMP_ARGS=$(mktemp /tmp/img2webp_args.XXXXXX.txt)
trap "rm -f '$TEMP_ARGS'" EXIT
echo "Finding frames matching: $INPUT_PATTERN"
# Find all matching files and sort them naturally
FRAME_COUNT=$(find "$DIRECTORY" -maxdepth 1 -name "$PATTERN" -type f | wc -l)
if [ "$FRAME_COUNT" -eq 0 ]; then
echo "Error: No frames found matching pattern: $INPUT_PATTERN"
exit 1
fi
echo "Found $FRAME_COUNT frames"
# Create argument file with optimal settings
cat > "$TEMP_ARGS" <<EOF
-lossless
-m 6
-d 100
-kmin 10
-kmax 100
-exact
-loop 0
-v
-o
$OUTPUT_FILE
EOF
# Append sorted frame list (using natural sort for proper ordering)
find "$DIRECTORY" -maxdepth 1 -name "$PATTERN" -type f | sort -V >> "$TEMP_ARGS"
echo "Creating animated WebP with settings:"
echo " - Lossless compression with maximum effort (-m 6)"
echo " - 10 fps (100ms per frame)"
echo " - Temporal optimization for screenshots (kmin=10, kmax=100)"
echo " - Exact color preservation in transparent areas"
echo " - Infinite loop"
echo ""
echo "This may take a while for large frame counts..."
echo ""
# Run img2webp with argument file
if img2webp "$TEMP_ARGS"; then
echo ""
echo "Success! Created: $OUTPUT_FILE"
# Show file size
if [ -f "$OUTPUT_FILE" ]; then
SIZE=$(du -h "$OUTPUT_FILE" | cut -f1)
echo "File size: $SIZE"
fi
else
echo ""
echo "Error: img2webp failed"
exit 1
fi
