bugMyPaint - Bugs: bug #18823, Jagged lines at zoom out (mouse...

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bug #18823: Jagged lines at zoom out (mouse whell)

Submitted by:  Grigore Florin <numarul7>
Submitted on:  Wed Oct 19 11:21:23 2011  
Severity: 3 - NormalPriority: 5 - Normal
Status: Need InfoPrivacy: Public
Assigned to: NoneOpen/Closed: Open
Release: 0.9.1-and GitPlanned Release: None
Operating System: Ubuntu64 bit oneiric

Wed Oct 19 18:58:02 2011, comment #4:

PS: the people who develop graphic drivers or 3D/2D hardware accelerated code are likely know what can cause those kind of problems. I'm a bit clueless here...

Martin Renold <martinxyz>
Project Administrator
Wed Oct 19 18:50:03 2011, comment #3:

A little bit of background info: MyPaint will do the zoom-out fully in software (via software mipmap code) if the zoom level is a multiple of 2 (every 2nd zoom step).

For the zoom-levels in-between (and also for rotation) it will ask the Cairo library to render the transformed bitmap, which has the ability to use hardware acceleration (via X11 backend at least).

We can control the hardware flags (to some extent) for testing. Maybe you can find something out by enabling the commented-out code that sets interpolation flags, in gui/tileddrawwidget.py line 540? Maybe the problem happens only when translated by half a pixel, or something similar?

Martin Renold <martinxyz>
Project Administrator
Wed Oct 19 11:51:32 2011, comment #2:

Oh, one other thing: please could you attach your configuration file from Ubuntu? It's in .mypaint/settings.json and you might want to edit it before posting since it contains paths to verious things (the Ubuntu Text Editor, gedit will work). That'll help complete the picture.

I wonder if a zoom setting is "off" somehow... It looks almost like a rounding error somewhere at a power of 2; that pattern of 4 vertical pixels looking "right" then a duplicate pair, and so on repeated.

(BTW, if I mention mipmaps, it's unlikely to be a graphics card thing. Mypaint's mipmaps are just precached numpy arrays)

Andrew Chadwick <achadwick>
Project Administrator
Wed Oct 19 11:45:28 2011, comment #1:

Grigore, hi -- enormous thanks for making a full bug report. I know it's a pain in the ass, but it does help and it makes sure that information isn't lost in IRC chaff and disconnects.

I can't replicate that with my settings here even with the test file you sent, unfortunately: I think I see the same things as you do with Win32 and 64.

You mentioned that it was happening at odd (or even) zoom levels on IRC. Correct me if I'm wrong. BTW: all odd (or even) zoom levels?

You also mentioned on IRC that the "High quality zoom" setting doesn't fix this. I can see something like this, but only just, if I have the setting turned off and zoom out quite a lot (note to self: show the zoom levels somehow).

/me will be able to test under Oneiric/amd64... shortly.

Andrew Chadwick <achadwick>
Project Administrator
Wed Oct 19 11:21:23 2011, original submission:

It happens only on Ubuntu and not on Win32/64 tested on both system. On Win32/64 the line is smooth and going to little blurry on mouse wheel zoom(no problem with this) but on Ubuntu i found that the line is transformed to a jagged line. This happens with mypaint git and 0.9.1 from the ubuntu repo.

Grigore Florin <numarul7>


Attached Files
file #14230:  jagged-line.ora added by numarul7 (28kB - image/openraster)
file #14231:  Screenshot-zoom.png added by numarul7 (210kB - image/png)
file #14232:  Screenshot-unzoom.png added by numarul7 (217kB - image/png)


Depends on the following items: None found

Items that depend on this one: None found


Carbon-Copy List
  • -unavailable- added by martinxyz (Posted a comment)
  • -unavailable- added by achadwick (Posted a comment)
  • -unavailable- added by numarul7 (Submitted the item)

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    Follow 5 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Wed Oct 19 11:45:28 2011achadwickSeverity5 - Blocker=>3 - Normal
      StatusNone=>Need Info
    Wed Oct 19 11:21:24 2011numarul7Attached File-=>Added jagged-line.ora, #14230
      Attached File-=>Added Screenshot-zoom.png, #14231
      Attached File-=>Added Screenshot-unzoom.png, #14232
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