ffmpeg to gif animation but better than stackoverflow - better color selection / pallete gen

togif.sh

#!/usr/bin/env bash
# Usage: ./mkv2gif.sh input.mkv output.gif [start] [end] [fps] [width]
# Example: ./mkv2gif.sh delme.mkv delout.gif 00:00:22.5 00:01:12 12 640
#
#
# Option Purpose
# stats_mode=full
# Scans every frame to build one histogram → true global palette. Use diff instead if the background is mostly static (screen recordings) — it only considers pixels that changed, which is usually better for screencasts.
# max_colors=256
# Fills all 256 slots (default).
# dither=sierra2_4a
#
# Good quality/speed tradeoff. For screen recordings with flat UI colors:
# dither=none or dither=bayer:bayer_scale=5 to avoid grain.
#
# diff_mode=rectangle
# Only re-encodes the changed rectangle per frame → smaller GIFs, ideal for screencasts.
#
# flags=lanczos
# High-quality downscaling.
#
# Recommended variants by content type:
#   Screen recording (UI, code, terminal) — usually best quality:
#   palettegen=stats_mode=diffpaletteuse=dither=bayer:bayer_scale=5:diff_mode=rectangle
#
#   photographic
#   palettegen=stats_mode=fullpaletteuse=dither=sierra2_4a
#
#   Absolutely no dithering (pure color quantization):
#   palettegen=stats_mode=fullpaletteuse=dither=none

INPUT="${1:?Usage: $0 input.mkv output.gif [start] [end] [fps] [width]}"
OUTPUT="${2:?Missing output filename}"
START="${3:-0}"
END="${4:-}"
FPS="${5:-12}"
WIDTH="${6:-640}"

# Build time args
TIME_ARGS=(-ss "$START")
[[ -n "$END" ]] && TIME_ARGS+=(-to "$END")

PALETTE="/tmp/palette_$$.png"
trap 'rm -f "$PALETTE"' EXIT

# Common filter chain (keep in sync between passes)
VF="fps=${FPS},scale=${WIDTH}:-1:flags=lanczos"

echo "=== Pass 1: Building global palette from entire clip ==="
ffmpeg -y "${TIME_ARGS[@]}" -i "$INPUT" \
    -vf "${VF},palettegen=max_colors=256:stats_mode=full" \
    "$PALETTE"

echo "=== Pass 2: Encoding GIF with global palette ==="
ffmpeg -y "${TIME_ARGS[@]}" -i "$INPUT" -i "$PALETTE" \
    -lavfi "${VF} [x]; [x][1:v] paletteuse=dither=sierra2_4a:diff_mode=rectangle" \
    -an "$OUTPUT"

echo "Done → $OUTPUT"
ls -lh "$OUTPUT"