what version of Matplotlib, what backend, and what OS?

@tacaswell Matplotlib: 2.1.1, Python: 3.6.4, OS: Windows 10 16299

Not only pictures, but also the toolbar is not clear.

Can you tell the difference? The second picture is much cleaner, with dpi = 300

Can you try with qt5agg instead of tkagg? (add import matplotlib; matplotlib.use("qt5agg") at the very top of your script; you may need to install pyqt5 from conda or pypi.)

@reaCodes is this still an issue? Did you get a chance to try out @anntzer's suggestion?

On master: tkagg is blurry. qt5agg is sharp (150%, 200% tested). Holds for icons and plot itself.

I think this is essentially a duplicate of #10388. Even though this issue was opened first I'll close it as there is more discussion on the other.
Feel free to reopen if you think a separate issue is warranted.

Actually let's keep this open for discussing the Windows case because the solution is likely OS-specific...

@timhoffm (or anyone else, for that matter) If you have a high-dpi screen available to testing on Windows, can you try calling one of https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setprocessdpiaware https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setprocessdpiawarenesscontext in tkagg.cpp? (e.g. at the top of PyInit__tkagg)
(also https://bugs.python.org/issue33656 suggests how to do this with ctypes)

@anntzer will do some time later this week.

Support for HiDPI in TkAgg on Windows was added in #19167.