Animations with gifsicle... plus complications

Some years ago, I discovered the excellent gifsicle, which I've used a few many times to create animated GIFs, like this sunrise at Zabreski Point. Today I did a slightly(?) more difficult one, made harder because I was snapping away with a phone, and about half-way through I changed the phone's orientation, switching from “portrait” (tall) to “landscape” (wide) images. It also didn't help that I know only the basics of image files. The good news, though, is that Imagemagick’s amazing convert(1) program has every capability we need to give gifsicle what it needs for a reasonable-looking animation. But I’m getting ahead of myself.

At first, I did what came naturally: downloaded the photos, converted them all to "gif"s, and told gifsicle to create the animated gif. Well, it was a disaster. Not a real disaster (no animals were harmed), but the animation started out in portrait mode and then switched to… Bad. The original files didn't tell me that though!

collin@collin-t450:/tmp/iCloud Photos$ file IMG_*.JPG | sed -e 's/Exif.*one 6,//' -e 's/xresolution.*precision 8,//'
IMG_0733.JPG: JPEG image data,  orientation=upper-right,  3264x2448, components 3
IMG_0734.JPG: JPEG image data,  orientation=upper-right,  3264x2448, components 3
IMG_0735.JPG: JPEG image data,  orientation=upper-right,  3264x2448, components 3
IMG_0736.JPG: JPEG image data,  orientation=upper-right,  3264x2448, components 3
IMG_0737.JPG: JPEG image data,  orientation=upper-right,  3264x2448, components 3
IMG_0738.JPG: JPEG image data,  orientation=upper-right,  3264x2448, components 3
IMG_0739.JPG: JPEG image data,  orientation=upper-right,  3264x2448, components 3
IMG_0740.JPG: JPEG image data,  orientation=upper-left,  3264x2448, components 3
IMG_0741.JPG: JPEG image data,  orientation=upper-left,  3264x2448, components 3
IMG_0742.JPG: JPEG image data,  orientation=upper-left,  3264x2448, components 3
IMG_0743.JPG: JPEG image data,  orientation=upper-left,  3264x2448, components 3
IMG_0744.JPG: JPEG image data,  orientation=upper-left,  3264x2448, components 3
collin@collin-t450:/tmp/iCloud Photos$ 

The “sed ...” removes a bunch of “TIFF image data...” stuff that was the same for all the files; I wanted the above output more readable. The thing I want you to notice is that all the image files are supposedly 3264x2248 pixels. Now there is a clue in the “orientation=” stuff, but as I said, I know only very basic stuff about these things.

Now part of my process (i.e., when doing what came naturally) was to convert these JPEG files to GIFs. I think I did something like

for F in IMG*JPG; do convert $F ${F%.JPG}.gif; done

After that, the switch from portrait to landscape became more obvious:

collin@collin-t450:/tmp/iCloud Photos$ file IMG*gif
IMG_0733.gif: GIF image data, version 89a, 2448 x 3264
IMG_0734.gif: GIF image data, version 89a, 2448 x 3264
IMG_0735.gif: GIF image data, version 89a, 2448 x 3264
IMG_0736.gif: GIF image data, version 89a, 2448 x 3264
IMG_0737.gif: GIF image data, version 89a, 2448 x 3264
IMG_0738.gif: GIF image data, version 89a, 2448 x 3264
IMG_0739.gif: GIF image data, version 89a, 2448 x 3264
IMG_0740.gif: GIF image data, version 89a, 3264 x 2448    ←landscape begins here
IMG_0741.gif: GIF image data, version 89a, 3264 x 2448
IMG_0742.gif: GIF image data, version 89a, 3264 x 2448
IMG_0743.gif: GIF image data, version 89a, 3264 x 2448
IMG_0744.gif: GIF image data, version 89a, 3264 x 2448
collin@collin-t450:/tmp/iCloud Photos$ 

Now the good news is that when I switched from portrait to landscape, Sheri's head remained roughly centered and about the same distance from the top of the image. To cut to the chase, I wrote a shell “one-liner” like this:
collin@collin-t450:/tmp/iCloud Photos$ for F in IMG_07*gif; do NEW=new${F#IMG_}; if file $F | grep "3264 x"; then C='2448x2448+408+0!' ; else C='2448x2448+0+0!'; fi; convert $F -crop $C +repage -resize 50% -remap IMG_0733.gif $NEW; done
which I'll explain tersely because it's time to go do something with the lovely Carol.

1. NEW=new${F#IMG_} makes $NEW to be $F except with new replacing IMG_. So new0733.gif for example
2. we check for landscape (those 3264 x 2448 images), and change the cropping parameter to fit the orientation of the original; that's what the C= stuff is.
3. we need +repage to make the “canvas size” fit the image boundaries. No, I don't really know what that means. But if I don't do it, everything looks weird.
4. -remap is so that all the new files will share the same colormap. Because gifsicle requires that.

then to make the animation,

collin@collin-t450:/tmp/iCloud Photos$ gifsicle -d 20 new*gif -o foo.gif

you can see the result on facebook if you’re Sheri’s “friend” there.