How do we use stream and convert commands together in imagemagick

I do understand from the imagemagick documentation that we do use stream command for processing large images.

Imagemagick Stream Interface

The question i have is: how do we use the stream command in conjunction with the convert command. Can we pipe the output of stream command to convert command or stream alone should be sufficient to achieve the needed transformations (eg: crop and resize)

Can someone provide any sample command ?? or maybe some material where i can find this ? let us say for a crop and resize use case ?

Thanks.

I did some timings of various ways to extract a 100x100 area from the bottom-right corner of a 12000x10000 image then resize it to 50x50 and save.

Make 200MB JPEG

magick -size 12000x10000 xc: +noise random a.jpg

Crop and resize with straight ImageMagick:

time magick a.jpg -crop 100x100+8000+8000 -resize 50 result.jpg
real	0m 2.38s
user	0m 2.10s
sys	    0m 0.27s

Crop and resize with stream:

time magick stream -storage-type char -map rgb -extract 100x100+8000+8000 a.jpg - | magick -depth 8 -size 100x100 rgb:- -resize 50 result.jpg
real	0m 2.04s
user	0m 1.98s
sys	    0m 0.05s

Crop and resize with vips:

time  vips extract_area a.jpg .ppm 8000 8000  100 100 | vipsthumbnail --size 50x50 -o result.jpg stdin 
real	0m 1.61s
user	0m 1.52s
sys	    0m 0.08s

My conclusion is that there is little benefit to using stream in this case, and that vips is somewhat faster.

The TIFF format allows images to be saved in strips that an image processor can seek to, without reading all the intermediate stuff. This is helpful when extracting chunks not near the start of images. So I made a TIFF with rows-per-strip=500

magick -size 12000x10000 xc: +noise random -depth 8 -define tiff:rows-per-strip=500 a.tif

Then I repeated the 3 tests from above:

Crop and resize with straight ImageMagick:

time magick a.tif -crop 100x100+8000+8000 -resize 50 result.jpg
real	0m 0.83s
user	0m 0.44s
sys	    0m 0.38s

Crop and resize with stream:

time magick stream -storage-type char -map rgb -extract 100x100+8000+8000 a.tif - | magick -depth 8 -size 100x100 rgb:- -resize 50 result.jpg
real	0m 0.82s
user	0m 0.44s
sys	    0m 0.38s

Crop and resize with vips:

time  vips extract_area a.tif .ppm 8000 8000  100 100 | vipsthumbnail --size 50x50 -o result.jpg stdin 
real	0m 0.17s
user	0m 0.05s
sys	    0m 0.12s

My conclusion is that there is a definite benefit to using TIFF format and vips if you are trying to do this sort of thing.