takes an input gif, deletes every second frame, sets the delay to each frame plus the delay of the frame after it. Good for shrinking the size of gifs.

gif_frame_reduction.sh

#!/bin/bash

# Usage: ./reduce_gif_frames.sh input.gif output.gif

if [ $# -ne 2 ]; then
    echo "Usage: $0 input.gif output.gif"
    exit 1
fi

INPUT_GIF="$1"
OUTPUT_GIF="$2"

echo "Processing $INPUT_GIF..."

# Get frame count
FRAME_COUNT=$(gifsicle --info "$INPUT_GIF" | grep -c "image #")
echo "Original frame count: $FRAME_COUNT"

# Get delays for each frame
echo "Analyzing frame delays..."
DELAYS=()
for ((i=0; i<FRAME_COUNT; i++)); do
    DELAY=$(gifsicle --info "$INPUT_GIF" "#$i" | grep "delay" | sed 's/.*delay \([0-9]*\).*/\1/')
    if [ -z "$DELAY" ]; then
        DELAY=10  # Default delay if none specified
    fi
    DELAYS[i]=$DELAY
done

# Calculate new frame count
NEW_FRAME_COUNT=$(((FRAME_COUNT + 1) / 2))
echo "New frame count: $NEW_FRAME_COUNT"

# Build gifsicle command to create new GIF
GIFSICLE_CMD="gifsicle -U '$INPUT_GIF'"

for ((i=0; i<FRAME_COUNT; i+=2)); do
    # Calculate combined delay
    DELAY1=${DELAYS[i]}
    if [ $((i+1)) -lt $FRAME_COUNT ]; then
        DELAY2=${DELAYS[$((i+1))]}
    else
        DELAY2=0  # If odd number of frames, no second frame to add
    fi
    
    COMBINED_DELAY=$((DELAY1 + DELAY2))
    
    echo "Keeping frame $i with combined delay $DELAY1+$DELAY2=$COMBINED_DELAY"
    
    # Add frame with new delay to command
    GIFSICLE_CMD="$GIFSICLE_CMD --delay $COMBINED_DELAY '#$i'"
done

GIFSICLE_CMD="$GIFSICLE_CMD --colors 256 --optimize=3 --output '$OUTPUT_GIF'"

echo "Creating new GIF..."
eval $GIFSICLE_CMD

echo "Done! Created $OUTPUT_GIF with $NEW_FRAME_COUNT frames"
echo "Original duration preserved by combining frame delays"