Linux – webp animation to gif animation (cli)

animationarch linuxgifimagemagickwebp

I was surprised today to find apparently how difficult it is to go from a webp animation to gif animation. My GIMP 2.8.22 and ImageMagick 7.0.7-21 on linux 4.14.13-1-ARCH don't seem to support the format, and the only tool available in repos seem to be libwebp 0.4.1 which includes a decode tool that lets you extract individual frames to some image formats, none of them being gif (It's a licensing problem maybe?)

Anyway, I used the following script:

#!/bin/bash

DELAY=${DELAY:-10}
LOOP=${LOOP:-0}
r=`realpath $1`
d=`dirname $r`
pushd $d > /dev/null
f=`basename $r`
n=`webpinfo -summary $f | grep frames | sed -e 's/.* \([0-9]*\)$/\1/'`
pfx=`echo -n $f | sed -e 's/^\(.*\).webp$/\1/'`
if [ -z $pfx ]; then
    pfx=$f
fi

echo "converting $n frames from $f 
working dir $d
file stem '$pfx'"

for ((i=0; i<$n; i++)); do
    webpmux -get frame $i $f -o $pfx.$i.webp
    dwebp $pfx.$i.webp -o $pfx.$i.png
done

convert $pfx.*.png -delay $DELAY -loop $LOOP $pfx.gif
rm $pfx.[0-9]*.png $pfx.[0-9]*.webp
popd > /dev/null

Which creates a gif animation from the extracted frames of the file supplied in the first argument.

I tried it on this file and the resulting file was kind of artifacty. Is it proper form to post in this forum for suggestions of improvement of the procedure/invocations?

And: If there are custom tools for this conversion, please share your knowledge! 🙂

Best Answer

Your script works just fine, but you need to zero pad your individual frame names; otherwise it creates the gif with frames in a jumbled order. I fixed that and tried it on a few giphy webp animations (including your example) and the output is what you'd expect.

Below is just your script with two changes. First, an altered for loop to zero pad those frame filenames. Second, I added another webpinfo check to grab the frame duration and use that (if > 0) for DELAY (naively assuming that people aren't using variable frame durations):

#!/bin/bash

DELAY=${DELAY:-10}
LOOP=${LOOP:-0}
r=`realpath $1`
d=`dirname $r`
pushd $d > /dev/null
f=`basename $r`
n=`webpinfo -summary $f | grep frames | sed -e 's/.* \([0-9]*\)$/\1/'`
dur=`webpinfo -summary $f | grep Duration | head -1 |  sed -e 's/.* \([0-9]*\)$/\1/'`

if (( $dur > 0 )); then
    DELAY = dur
fi

pfx=`echo -n $f | sed -e 's/^\(.*\).webp$/\1/'`
if [ -z $pfx ]; then
    pfx=$f
fi

echo "converting $n frames from $f 
working dir $d
file stem '$pfx'"

for i in $(seq -f "%05g" 1 $n)
do
    webpmux -get frame $i $f -o $pfx.$i.webp
    dwebp $pfx.$i.webp -o $pfx.$i.png
done

convert $pfx.*.png -delay $DELAY -loop $LOOP $pfx.gif
rm $pfx.[0-9]*.png $pfx.[0-9]*.webp
popd > /dev/null

Related Solutions

ImageMagick – Creating a GIF Animation from PNG Files

Newer versions of ffmpeg have no -sameq (see faq) but do have GIF support.
ffmpeg -i %03d.png output.gif
Where %03d is the frame ID in 3 digits.

You may also try to use ffmpeg to create a movie out of a sequence of images and then convert the movie to a GIF animation (again using ffmpeg).

# cf. http://pages.uoregon.edu/noeckel/MakeMovie.html

# first convert an image sequence to a movie
ffmpeg -sameq -i %03d.jpg output.mp4

# ... and then convert the movie to a GIF animation
ffmpeg -i output.mp4 -pix_fmt rgb24 -s qcif -loop_output 0 output.gif

Remove nth frames of a gif (remove a frame every n frames)

There is probably a better way to do it, but here is what I would do

First, split your animation in frames

convert animation.gif +adjoin temp_%02d.gif

Then, select one over n frames with a small for-loop in which you loop over all the frames, you check if it is divisible by 2 and if so you copy it in a new temporary file.

j=0; for i in $(ls temp_*gif); do if [ $(( $j%2 )) -eq 0 ]; then cp $i sel_`printf %02d $j`.gif; fi; j=$(echo "$j+1" | bc); done

If you prefer to keep all the non-divisible numbers (and so if you want to delete rather than to keep every nth frame), replace -eq by -ne.

And once you done it, create your new animation from the selected frames

convert -delay 20 $( ls sel_*) new_animation.gif

You can make a small script convert.sh easily, which would be something like that

#!/bin/bash
animtoconvert=$1
nframe=$2
fps=$3

# Split in frames
convert $animtoconvert +adjoin temp_%02d.gif

# select the frames for the new animation
j=0
for i in $(ls temp_*gif); do 
    if [ $(( $j%${nframe} )) -eq 0 ]; then 
        cp $i sel_`printf %02d $j`.gif; 
    fi; 
    j=$(echo "$j+1" | bc); 
done

# Create the new animation & clean up everything
convert -delay $fps $( ls sel_*) new_animation.gif
rm temp_* sel_*

And then just call, for example

$ convert.sh youranimation.gif 2 20

Best Answer

Related Solutions

ImageMagick – Creating a GIF Animation from PNG Files

Remove nth frames of a gif (remove a frame every n frames)

Related Question