graphic: 0.825
mistranslation: 0.818
device: 0.814
risc-v: 0.806
semantic: 0.800
x86: 0.798
performance: 0.766
architecture: 0.714
files: 0.705
socket: 0.692
vnc: 0.691
VMM: 0.690
ppc: 0.686
permissions: 0.680
boot: 0.662
user-level: 0.661
network: 0.656
kernel: 0.644
i386: 0.619
virtual: 0.616
PID: 0.615
TCG: 0.611
register: 0.588
peripherals: 0.548
hypervisor: 0.548
arm: 0.487
debug: 0.474
KVM: 0.417
assembly: 0.350

qemu-img convert -c compression can't decompress

Used -c compression option of qemu-img convert to compress qcow2,
then libvirt mount for compressed image don't work as well as decompression also
not working, tried glib-deflate to decompress

Used openssl zlib -d < compressedfile but that also not working

When tried zlib-flate -uncompress < cirros-0.3.4-x86_64-disk.img,
getting below error

data: incorrect header check

Which version of QEMU (or rather qemu-img) are you using?

qemu-img version 2.1.2, Copyright (c) 2004-2008 Fabrice Bellard

When reporting bugs, please always use the latest version of QEMU, old versions like 2.1 are not supported anymore. I just also noticed that Stefan Hajnoczi replied to the bug mail on the qemu-devel mailing list (see https://<email address hidden>/msg422186.html) - seems like the bridge did not mirror this to the bug tracker:

"QEMU image compression uses the compression feature available in some
 disk image formats (like qcow2).  This is not the same as compressing a
 file with gzip, bzip2, or similar tools.
 Therefore this error is expected and not a bug."

Yes used qcow2 format only when compressing, I don't think due to older version problem

When converting qcow2 with -c option, then after not able to boot VM with compressed qcow2 image