ImageMagick Append Image sequence Filenames

Question

I am using the animation tool Synfig to export a sequence of .png files. These are in the following format: C1.0000.png , C1.0001.png, C1.0002.png and so on.

I want to convert these to a spritesheet (i.e. append all of them together) however, I also need the same animations but flipped.

Here's where I have the problem. When using the following syntax:

 convert C1.*.png -flop C1right.*.png

I don't get a sequence similar to what I had before. (C1right.0000.png, C1right.0001.png etc) but instead C1right.-0.png, C1right.-1.png, etc.

This on its own isn't that bad, but because the +append command sorts the images alphabetically and not numerically, I end up with a sequence where not image 2 follows image 1 but image 11 follows image 1, with 2 ending up after 19.

Is there any way to keep the original file name structure? Or is there a way to ensure that the +append sorts the files numerically?

Answer 1

Only using glob patterns will not do. You must loop on all files:

for f in C1*.png ;do convert $f -flop $(echo $f | sed 's/\./right./') ;done

This will execute like this:

convert C1.01000.png -flop C1right.01000.png
convert C1.01001.png -flop C1right.01001.png
convert C1.01002.png -flop C1right.01002.png

Answer 2

Use format specifier %04d (0 means zero left-padded, 4d means 4 decimal positions):

convert C1.*.png -flop C1right.%04d.png

The resulted names will be

C1right.0000.png
C1right.0001.png
C1right.0002.png

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Note: In ImageMagick version 7+ simply replace convert command with magick.