How to stitch back cropped image with imageMagick? - imagemagick

Question

I have a big big image, lets name it orig-image.tiff.
I want to cut it in smaller pieces, apply things on it, and stitch back together the newly created little images.
I cut it into pieces with this command :
convert orig-image.tiff -crop 400x400 crop/parts-%04d.tiff
then I'll generate many images by applying a treatment to each part-XXXX.tiff image and end up with images from part-0000.png to part-2771.png
Now I want to stitch back the images into a big one. Can imagemagick do that?

Answer 1

If you were using PNG format, the tiles would "remember" their original position, as #Bonzo suggests, and you could take them apart and reassemble like this:
# Make 256x256 black-red gradient and chop into 1024 tiles of 8x8 as PNGs
convert -size 256x256 gradient:red-black -crop 8x8 tile-%04d.png
and reassemble:
convert tile*png -layers merge BigBoy.png
That is because the tiles "remember" their original position on the canvas - e.g. +248+248 below:
identify tile-1023.png
tile-1023.png PNG 8x8 256x256+248+248 16-bit sRGB 319B 0.000u 0:00.000
With TIFs, you could do:
# Make 256x256 black-red gradient and chop into 1024 tiles of 8x8 as TIFs
convert -size 256x256 gradient:red-black -crop 8x8 tile-%04d.tif
and reassemble with the following but sadly you need to know the layout of the original image:
montage -geometry +0+0 -tile 32x32 tile*tif BigBoy.tif
Regarding Glenn's comment below, here is the output of pngcheck showing the "remembered" offsets:
pngcheck tile-1023*png
Output
OK: tile-1023.png (8x8, 48-bit RGB, non-interlaced, 16.9%).
iMac:~/tmp: pngcheck -v tile-1023*png
File: tile-1023.png (319 bytes)
chunk IHDR at offset 0x0000c, length 13
8 x 8 image, 48-bit RGB, non-interlaced
chunk gAMA at offset 0x00025, length 4: 0.45455
chunk cHRM at offset 0x00035, length 32
White x = 0.3127 y = 0.329, Red x = 0.64 y = 0.33
Green x = 0.3 y = 0.6, Blue x = 0.15 y = 0.06
chunk bKGD at offset 0x00061, length 6
red = 0xffff, green = 0xffff, blue = 0xffff
chunk oFFs at offset 0x00073, length 9: 248x248 pixels offset
chunk tIME at offset 0x00088, length 7: 13 Dec 2016 15:31:10 UTC
chunk vpAg at offset 0x0009b, length 9
unknown private, ancillary, safe-to-copy chunk
chunk IDAT at offset 0x000b0, length 25
zlib: deflated, 512-byte window, maximum compression
chunk tEXt at offset 0x000d5, length 37, keyword: date:create
chunk tEXt at offset 0x00106, length 37, keyword: date:modify
chunk IEND at offset 0x00137, length 0
No errors detected in tile-1023.png (11 chunks, 16.9% compression).