Extract

tar -xf path/to/...img.tar.gz

Find sdcard

Find the device name you want to apply the image on. Note that the name could be different on your system. In this example my sdcard is shown:

lsblk

NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
mmcblk0     179:0    0  59.6G  0 disk

Flash image to SD-Card

Make shure to identify the right device. This command overwrites target data:

sudo dd BS=4M if=path/to/extracted/...img of=/dev/mmcblk0

Resize image

Insert image to loop device

sudo modprobe loop
sudo losetup -f
sudo losetup /dev/loop0 myimage.img
sudo partprobe /dev/loop0

Resize partition on image

gparted /dev/loop0

Release loopdevice

sudo losetup -d /dev/loop0

Find last sector of image partition table

fdisk -l myimage.img

Disk /home/aaa/a3motion_aarch64.img: 59.63 GiB, 64021856256 bytes, 125042688 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x030c2c18

Device                             Start    End      Sectors  Size Id Type
/home/aaa/a3motion_aarch64.img1    2048     411647   409600   200M  c W95 FAT32 (LBA)
/home/aaa/a3motion_aarch64.img2    411648   8800255  8388608  4G  	83 Linux

Crop empty space from image

truncate --size=$[(8800255+1)*512] myimage.img

Compress image

tar -czvf name-of-archive.tar.gz /path/to/directory-or-file