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@dperelman dperelman/blend.sh
Created Mar 8, 2015

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What would you like to do?
Create simple slideshow video with blend effect between images.
#!/bin/sh
# Need at least an outfile and two images for this command to make sense.
if [ $# -lt 3 ]
then
echo USAGE: "$0" OUTFILE IMAGES...
echo Create simple slideshow video with blend effect between images.
echo
echo OUTFILE is video file to create, .mkv extension is recommended.
echo IMAGES is a sequence of images for the slideshow.
exit
fi
# 30 fps, so this means each original image corresponds to one second of video.
frames_per_image=30
fps=30
out="$1"
shift
# Create a temporary directory to store the frames in.
dir=$(mktemp -d)
# Iterate through the images keeping track of the previous one to be blended
# with the current one.
num=0 # frame number
prev='' # previous image or empty string if none
for image in "$@"
do
# If there is a previous image, blend with it.
if [ -f "$prev" ]
then
for fade_amount in $(seq 1 $((frames_per_image - 1)))
do
# Use bc for math to get decimals.
composite -blend "$(echo "$fade_amount/$frames_per_image*100" | bc -lq)" "$image" "$prev" "$dir/image$num"".png"
num=$((num + 1))
done
fi
# Always in include the actual image as one of the frames.
# Use convert so any image format will work.
convert "$image" "$dir/image${num}.png"
num=$((num + 1))
# Remember this image for the next iteration.
prev="$image"
done
# Encode the video from the frames.
# -pix_fmt yuv420p is normal pixel format, but default is yuv444p which
# ffmpeg warns might not be supported by all players.
ffmpeg -f image2 -i "$dir/image%d.png" -pix_fmt yuv420p -r "$fps" "$out"
# Delete the temporary directory with the frames.
rm -rf "$dir"
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