kuncevic/terminal-gif.md

## terminal-gif.md

      
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              terminal-gif.md
            
          
    Install ImageMagick

brew install ImageMagick
Pull specific region of frames from video file w/ ffmpeg

ffmpeg -ss 14:55 -i video.mkv -t 5 -s 480x270 -f image2 %04d.png

-ss 14:55 gives the timestamp where I want FFmpeg to start, as a duration string.

-t 5 says how much I want FFmpeg to decode, using the same duration syntax as for -ss.

-s 480x270 tells FFmpeg to resize the video output to 480 by 270 pixels.

-f image2 selects the output format, a series of still images — make sure there are leading zeros in filename.


Resize series of images

convert *.png -resize 70% newname%02d.png
Convert mutliple filetype(s) into animated gif

convert -delay 10 -loop 0 *.png anim.gif

convert -fuzz 1% -delay 1x8 *.png -coalesce -layers OptimizeTransparency animation.gif


-fuzz tells ImageMagick to treat pixels whose color values differ by less than 1% as the same color, giving the OptimizeTransparency action more pixels to chop away.

-delay 1x8 says that the animation should play a frame every 1/8 of a second.

-layers OptimizeTransparency tells ImageMagick to replace portions of each frame that are identical to the corresponding parts of the preceding frame with transparency, saving on file size.


convert -fuzz 1% -delay 10 -loop 0 *.png -coalesce -layers OptimizeTransparency animation.gif


Ping-pong Looping Method

convert script_k.gif -coalesce   -duplicate 1,-2-1 -quiet -layers OptimizePlus  -loop 0 patrol_cycle.gif


hypervoid force sizing + optimization:

convert -resize '1920x350!' -delay 5 -loop 0 *.png hv.gif

convert -fuzz 3% -resize '1920x350!' -delay 5 -loop 0 -coalesce -layers OptimizeTransparency *.png an.gif


this test yielded impressive reduction:

convert -filter Triangle -define filter:support=2 -thumbnail 1920 -delay 5 -loop 0 -unsharp 0.25x0.08+8.3+0.045 -dither None -posterize 136 -quality 82 -define jpeg:fancy-upsampling=off -define png:compression-filter=5 -define png:compression-level=9 -define png:compression-strategy=1 -define png:exclude-chunk=all -interlace none -colorspace sRGB *.png output.gif


another version with less color information

convert -filter Triangle -define filter:support=2 -thumbnail 1920 -delay 5 -loop 0 -unsharp 0.25x0.08+8.3+0.045 -dither None -posterize 136 -quality 82 -define jpeg:fancy-upsampling=off -define png:compression-filter=5 -define png:compression-level=9 -define png:compression-strategy=1 -define png:exclude-chunk=all -interlace none -colorspace sRGB -colors 32 -ordered-dither o8x8,8,8,8,4 +map *.png output.gif
convert GIF into movie by extracting frames and recompiling

convert -coalesce some.gif some%05d.png

extract gif frames
ffmpeg -i some%05d.png some.mov

converting image sequence in QuickTime 7 worked more effectively than the above command
rm some*.png

clear extracted frames
Pull apart GIF

convert -coalesce animation.gif target.png
Cropping / Batch Crop

If you want the crop rectangle to start at top corner X: 50 Y: 100 and the crop rectangle to be of size W: 640 H:480, then use the command:

$ mogrify -crop 640x480+50+100 foo.png


To write the cropped image to a new file:

$ convert foo.png -crop 640x480+50+100 out.png


batch conversion:

for i in *.png; do convert "$i" -crop 1920x248+0+400 "${i%.png}-cropped.png"; done


more information about the convert command

and here

and here