v0.1.2 Flicker test bash script

This bash script uses the lossless animated Webp to create a loop to compare Webp and JXL to each other and a source PNG.
The Webp/JXL filenames are overlaid to display hidden info (ie filesize/CVVDP score/encoding parameters).
sRGB signaling is enforced for all images and finally temporary PNG intermediate files are deleted.

#!/usr/bin/env bash

for f in in.png; do
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i "$f" \
-vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=20:y=20" \
-pix_fmt rgb24 png.png
done

for f in *.webp; do
dwebp -quiet "$f" -o decwebp.png
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i decwebp.png \
-vf "drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=(w-text_w)/2:y=20" \
-pix_fmt rgb24 webp.png
done

for f in *.jxl; do
djxl "$f" decjxl.png --quiet
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i decjxl.png \
-vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=w-text_w-20:y=20" \
-pix_fmt rgb24 jxl.png
done

img2webp -lossless -m 6 -loop 0 -d 1000 png.png webp.png jxl.png -o Webp-vs-JXL_flicker.webp
rm -f png.png decwebp.png webp.png decjxl.png jxl.png

Dependencies: FFmpeg, libwebp, and libjxl

2026-08-16·06:19·No.1376

CVVDP-9.5_Webp-vs-JPG_flicker.webp

This is not meant to treat JXL as entirely inferior to Webp, just show that even though CVVDP is a state of the art high fidelity image quality metric, it is not perfect.
Explicit sRGB signaling is important for image testing as FFmpeg will not assume it by default. FFMPEG PNGs generated without it can suffer from incorrect brightness/gamma.

I am also using this Webp vs JPG variant in a botched LOSSY JPG/Webp/JXL/AVIF comparison thread I'm currently debugging that also suffered from incorrect colorspace assumptions.

#!/usr/bin/env bash

for f in in.png; do
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i "$f" \
-vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=20:y=20" \
-pix_fmt rgb24 png.png
done

for f in *.webp; do
dwebp -quiet "$f" -o dwebp.png
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i dwebp.png \
-vf "drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=(w-text_w)/2:y=20" \
-pix_fmt rgb24 webp.png
done

for f in *.jpg; do
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i "$f" \
-vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=w-text_w-20:y=20" \
-pix_fmt rgb24 jpg.png
done

img2webp -lossless -m 6 -loop 0 -d 1000 png.png webp.png jpg.png -o Webp-vs-JPG_flicker.webp
rm -f png.png dwebp.png webp.png jpg.png

2026-08-16·12:41·No.1378

Keep up the good work👍

[Catalog]

2/1

v0.1.2 Flicker test bash script

#!/usr/bin/env bash

for f in in.png; do
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i "$f" \
-vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=20:y=20" \
-pix_fmt rgb24 png.png
done

for f in *.webp; do
dwebp -quiet "$f" -o decwebp.png
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i decwebp.png \
-vf "drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=(w-text_w)/2:y=20" \
-pix_fmt rgb24 webp.png
done

for f in *.jxl; do
djxl "$f" decjxl.png --quiet
ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i decjxl.png \
-vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=w-text_w-20:y=20" \
-pix_fmt rgb24 jxl.png
done

img2webp -lossless -m 6 -loop 0 -d 1000 png.png webp.png jxl.png -o Webp-vs-JXL_flicker.webp
rm -f png.png decwebp.png webp.png decjxl.png jxl.png

Dependencies: FFmpeg, libwebp, and libjxl

#!/usr/bin/env bash for f in in.png; do ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i "$f" \ -vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=20:y=20" \ -pix_fmt rgb24 png.png done for f in *.webp; do dwebp -quiet "$f" -o dwebp.png ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i dwebp.png \ -vf "drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=(w-text_w)/2:y=20" \ -pix_fmt rgb24 webp.png done for f in *.jpg; do ffmpeg -hide_banner -loglevel error -color_primaries bt709 -color_trc iec61966-2-1 -i "$f" \ -vf "format=rgb24,drawtext=text='$(basename "$f")':fontcolor=white:fontsize=12:box=1:[email protected]:boxborderw=8:x=w-text_w-20:y=20" \ -pix_fmt rgb24 jpg.png done img2webp -lossless -m 6 -loop 0 -d 1000 png.png webp.png jpg.png -o Webp-vs-JPG_flicker.webp rm -f png.png dwebp.png webp.png jpg.png