Results 1 to 3 of 3

Thread: Achieving better graphics quality in Qwt charts

  1. #1
    Join Date
    Jun 2018
    Posts
    2
    Thanks
    1
    Qt products
    Qt5
    Platforms
    Windows

    Question Achieving better graphics quality in Qwt charts

    Dear Forum,

    I've been happily using Qwt in C++ for some time. Though, the quality of the graphics (plot lines etc.) in Qwt doesn't visually satisfy me as much as say Matlab or Matplotlib (Python) does. If you take a look at this video, where Matplotlib and PyQwt are showcased side by side, you'll notice that the graphics quality of the lines in Matplotlib is somewhat better than Qwt's. I've played around with anti-aliasing, line thicknesses, cap styles and such, but I've been unable to get a look closer to what Matplotlib or Matlab can offer out of the box. What I want to achieve is smooth, quality-looking lines in Qwt.

    I'd appreciate any input on the subject.

    Best regards.

  2. #2
    Join Date
    Feb 2006
    Location
    Munich, Germany
    Posts
    3,100
    Thanked 806 Times in 755 Posts
    Qt products
    Qt3 Qt4 Qt/Embedded
    Platforms
    MacOS X Unix/X11 Windows

    Default Re: Achieving better graphics quality in Qwt charts

    The performance and quality of rendering lines depends on the graphic stack you have set up on your system and the attributes of your pen. So this discussion is about Qt and more or less unrelated to Qwt.

    In general Qt offers OpenGL, Raster or X11 as graphic systems. Usually Raster gives nicer results than OpenGL with multisampling, but this is up to you to decide.
    X11 has been removed with Qt5, so you need to use Qt4 if you want to check it ( IMHO X11 was the best option ).

    X11 and OpenGL are hardware accelerated so the result might also depend on your hardware or drivers, while the raster paint engine is a pure software renderer and you should have the same results on all platforms. See https://doc.qt.io/archives/qt-4.8/qa...GraphicsSystem

    PyQwt is pretty outdated and completely unmaintained - I would recommend to use https://github.com/GauiStori/PyQt-Qwt instead.

    If you not happy with the quality of the lines being rendered from the raster paint engine you can try to contact the Qt development.

    Uwe

  3. The following user says thank you to Uwe for this useful post:

    bilgilid (14th June 2018)

  4. #3
    Join Date
    Jun 2018
    Posts
    2
    Thanks
    1
    Qt products
    Qt5
    Platforms
    Windows

    Default Re: Achieving better graphics quality in Qwt charts

    Quote Originally Posted by Uwe View Post
    The performance and quality of rendering lines depends on the graphic stack you have set up on your system and the attributes of your pen. So this discussion is about Qt and more or less unrelated to Qwt.

    In general Qt offers OpenGL, Raster or X11 as graphic systems. Usually Raster gives nicer results than OpenGL with multisampling, but this is up to you to decide.
    X11 has been removed with Qt5, so you need to use Qt4 if you want to check it ( IMHO X11 was the best option ).

    X11 and OpenGL are hardware accelerated so the result might also depend on your hardware or drivers, while the raster paint engine is a pure software renderer and you should have the same results on all platforms. See https://doc.qt.io/archives/qt-4.8/qa...GraphicsSystem

    PyQwt is pretty outdated and completely unmaintained - I would recommend to use https://github.com/GauiStori/PyQt-Qwt instead.

    If you not happy with the quality of the lines being rendered from the raster paint engine you can try to contact the Qt development.

    Uwe
    Thanks Uwe. I've found in Qt5 docs that "The primary paint engine provided is the raster paint engine..."

    But I do understand that this is more on the Qt side than Qwt, as you said. I'll try getting help from the Qt dev team on the matter.

Similar Threads

  1. Replies: 21
    Last Post: 8th December 2011, 02:18
  2. Charts in Qt!!
    By rachana in forum Qt Programming
    Replies: 3
    Last Post: 6th May 2011, 06:10
  3. Help with Bar charts
    By romeo in forum Qwt
    Replies: 0
    Last Post: 30th June 2010, 16:58
  4. MVC charts for Qt4
    By wysota in forum Qt-based Software
    Replies: 8
    Last Post: 28th September 2006, 16:06

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Digia, Qt and their respective logos are trademarks of Digia Plc in Finland and/or other countries worldwide.