I would just use Pillow:

from PIL import ImageGrab
im = ImageGrab.grabclipboard()
im.save('somefile.png','PNG')

I did copy the code and replace the StringIO with BytesIO and it worked! (with *.jpg and *.png files) Thank you so much!

from io import BytesIO
import win32clipboard
from PIL import Image

def send_to_clipboard(clip_type, data):
    win32clipboard.OpenClipboard()
    win32clipboard.EmptyClipboard()
    win32clipboard.SetClipboardData(clip_type, data)
    win32clipboard.CloseClipboard()

filepath = 'Ico2.png'
image = Image.open(filepath)

output = BytesIO()
image.convert("RGB").save(output, "BMP")
data = output.getvalue()[14:]
output.close()

send_to_clipboard(win32clipboard.CF_DIB, data)

scrot + xclip

You can use scrot with xclip to take a screenshot and copy it to clipboard.

scrot '/tmp/%F_%T_$wx$h.png' -e 'xclip -selection clipboard -target image/png -i $f'

It will capture whole of your screen and copy the image to clipboard. If you want to capture current window then use -u flag. For selection of particular area, you can add -s flag. See $ man scrot for more options.

It will store your screenshot in /tmp directory. You can change that directory wherever you want it to get stored. Files from /tmp directory usually gets deleted after each reboot. If you want to immediately remove the stored file, then do something like:

scrot -w '/tmp/%F_%T_$wx$h.png' -e 'xclip -selection clipboard -target image/png -i $f && rm $f'

As I read in other comments, you need it for copying a screenshot to the clipboard. I hope this answers your question.

If you just need to copy an already existing image file to clipboard:

cat 2018-06-16-224938_670x730_scrot.png | xclip -selection clipboard -target image/png -i

You can set keyboard shortcuts/keybindings according to your current Desktop Environment/window manager.

Bonus

Explanation of /tmp/%F_%T_$wx$h.png:

It's being used as the file name. These are called format specifiers. They are of two type: starting with % or $.

%F     Equivalent to %Y-%m-%d (the ISO 8601 date format).

%T     The time in 24-hour notation (%H:%M:%S).

%F_%T_ will print something like: 2018-06-17_02:52:19_ i.e. your current timestamp. You can customize the format as per your requirements. See $ man strftime for more help.

$wx$h are part of the scrot's internal specifiers.

$w   image width
$h   image height

So the final file name will look something like 2018-06-17_02:52:19_1365x384.png.

xclip

xclip (man page) is on official repos of major distros (pasteimg it isn't and last update was on 2011).

For me the quickest way is using terminal, going to the desired folder (maybe using Z) and then just run clipboard2photo, which is an alias I created to the following command:

xclip -selection clipboard -t image/png -o > "$(date +%Y-%m-%d_%T).png"  # Use "Screenshot from $(date "+%Y-%m-%d %H-%M-%S").png" if you like GNOME filename format.

To save in JPEG format instead of PNG using imagemagick:

f="$(date '+%Y-%m-%d_%T').png" && xclip -selection clipboard -t image/png -o > "$f" && mogrify -format jpg "$f" && rm "$f" && unset "f"

With something on clipboard you can get all possible targets with: xclip -selection clipboard -o -t TARGETS.

GNOME Files/Nautilus

GNOME v44 let you paste directly from clipboard to Files/Nautilus.

GNOME Shell shortcuts

On GNOME Shell (Ubuntu 17.10+) we have built in shortcuts to save screenshots directly to ~/Pictures:

Hints to remember them:

• Ctrl → to clipboard (else to ~/Pictures)
• Alt → Current window
• Shift → Area/Surface

I usually disable "Print" to avoid generating garbage on ~/Pictures if I miss F12 (which I use a lot with Guake) and accidentally press it.

Tip 1: Put your aliases on ~/sync_folder/.mybashrc (or maybe better .myprofile; where sync_folder might be Nextcloud or any other service) and then include this file from .bashrc.

[ -r ~/sync_folder/.mybashrc ] && source ~/sync_folder/.mybashrc

This way you will have them on all your current and future devices. Of course, you can also have a ~/.dotfiles with a git repo.

Tip 2: In the same way, you can: thisOutputMarkdown | pandoc -s -f markdown -t html | xclip -selection clipboard -t text/html to get formatted HTML to clipboard.
If you have the Markdown text on clipboard replace thisOutputMarkdown with xsel -b.

Wayland

It seems there is some work to be done about xclip on Wayland (echo $XDG_SESSION_TYPE). Please help developers on this issue. Meanwhile, maybe wl-paste (from wl-clipboard) might work:

wl-paste -t image/png > "$(date +%Y-%m-%d_%T).png"

For ImageGrab to save the clipboard

How!

Run on python==2.7 pillow==2.7.0

from PIL import ImageGrab, Image
im= ImageGrab.grabclipboard()
if isinstance(im, Image.Image):
    im.save('tmp.jpg')

Why?

IOError: Unsupported BMP bitfields layout

Reproducible with Pilllow 2.8.0, 2.8.1, 2.8.2. Not reproducible with Pillow 2.6.0, 2.7.0 https://github.com/python-pillow/Pillow/issues/1293

Notice

sorry to notice that is was only work on windows