How to dump the userdata partition into an image form a samsung galaxy s6 without rooting the phone

this is still a WIP, no confirmation that this actually leads to a useful image.. i am currently waiting for the image to be completely downloaded first things first.. the process involved in this could also be used to root your phone, but suppose you don't want to root your phone to keep it stock and to receive all those ota updates in the future without issue, this is a method where your phone will not be modified in any way but you can still dump a partition into a file in order to restore lost images or do other stuff with it.

you will need a windows pc for the odin step.. if you don't have a windows computer available, you might try to use “Heimdall” which should be able to do the same i've read.. however, on a rare occation a did have a windows pc available, so i stuck to odin ;)

download latest odin
go to http://twrp.my and download the .tar image for your phone (take the compressed tar, not the .img file please)
now boot into odin mode by turning off the phone, then hold volume down + home + power until you get a message where you can confirm you want to enter the odin mode by pushing volume up
now start odin, connect your phone and slect your tar file in the “AP” field. make sure that none of the boxes except for the “F. reset” are ticked in the optionis, not even the auto reboot option!
flash twrp to your phone
when odin reports success, press all buttons on your phone together and hold them until the screen goes dark
immediately after the screen went dark, hold the volume up + home + power and your phoen will boot into twrp. if you miss this step and the phone boots normally it will automatically replace twrp with its normal recovery image and you need to flash twrp again.
once you are in twrp, connect to your phone via adb

adb shell
ls -al /dev/block/platform/15570000.ufs/by-name/
<code> will give you a handy list of what partition holds what kind of data in order to decide which you want to dump.. i went for the one holding USERDATA as this is where i can proabably find those lost images. on my phone that was linked to /dev/block/sda18, so i ran this command (from the linux machine running adb): 
  * <code>adb shell 'stty raw && dd if=/dev/block/sda18' > /root/martina.img

make sure you have some other hobbies that you can attend to for the moment, as this will take very long! my phone could download about 4 GB in 10 minutes.. so suppose this is probably a 128GB phone and most of the space is reserved for user data, this can take several hours..