compilation error, YUV420toYUV444 function is missing

[nazikus]

compilation error:

$ gcc v4l2grab.c -o v4l2grab -Wall -ljpeg -lv4l2 -DIO_READ -DIO_MMAP -DIO_USERPTR

/tmp/user/1000/ccIvliiI.o: In function `imageProcess':
v4l2grab.c:(.text+0x374): undefined reference to `YUV420toYUV444'
collect2: error: ld returned 1 exit status

Having gcc v7.3 and following v4l packages installed:

$ apt list --installed | grep v4l

libv4l-0/bionic,now 1.14.2-1 amd64 [installed]
libv4l-dev/bionic,now 1.14.2-1 amd64 [installed]
libv4l2rds0/bionic,now 1.14.2-1 amd64 [installed]
libv4lconvert0/bionic,now 1.14.2-1 amd64 [installed]
v4l-conf/bionic,now 3.103-4build1 amd64 [installed]
v4l-utils/bionic,now 1.14.2-1 amd64 [installed]
v4l2loopback-dkms/bionic,bionic,now 0.10.0-1ubuntu1 all [installed]
v4l2loopback-source/bionic,bionic,now 0.10.0-1ubuntu1 all [installed]
v4l2loopback-utils/bionic,now 0.10.0-1ubuntu1 amd64 [installed]
v4l2ucp/bionic,now 2.0.2-4build1 amd64 [installed]

[twam]

YUV420toYUV444 is defined in yuv.c which you need to compile and link as well. Please follow the instructions on https://github.com/twam/v4l2grab/wiki/Installation