bugThe FreeType Project - Bugs: bug #46551, Severe colorful subpixel artifacts

 
 

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bug #46551: Severe colorful subpixel artifacts

Submitter:  Alexei Podtelezhnikov <podtelez>
Submitted:  Fri 27 Nov 2015 02:56:14 AM UTC
   
 
Severity:  3 - Normal Item Group:  None
Status:  Fixed Privacy:  Public
Assigned to:  None Open/Closed:  Closed
Planned Release:  None

Mon 30 Nov 2015 02:46:04 PM UTC, comment #3: 

Fixed in git.

Alexei Podtelezhnikov <podtelez>
Group Member
Mon 30 Nov 2015 04:26:06 AM UTC, comment #2: 

I think I am onto something. I've managed to segfault ftview just by switching to cyan-on-cyan rendering. I know it is silly as you won't be able to see anything, but I was not expecting to see Segmentation Fault. I cannot find the dumped core file and I do not know how to debug those either. Can you help? These are the steps to reproduce:

1. Apply this patch:

--- a/src/ftcommon.c
+++ b/src/ftcommon.c
@@ -111,9 +111,9 @@
     display->bitmap  = &surface->bitmap;

     display->fore_color = grFindColor( display->bitmap,
-                                       0x00, 0x00, 0x00, 0xff );
+                                       0x00, 0xff, 0xff, 0xff );
     display->back_color = grFindColor( display->bitmap,
-                                       0xff, 0xff, 0xff, 0xff );
+                                       0x00, 0xff, 0xff, 0xff );
     display->warn_color = grFindColor( display->bitmap,
                                        0xff, 0x00, 0x00, 0xff );


2. Switch to vRGB by pressing [C]. Boom!

Alexei Podtelezhnikov <podtelez>
Group Member
Fri 27 Nov 2015 05:27:26 AM UTC, comment #1: 

Some time ago I have noticed an effect similar to this, which comes up from time to time, but i was never able to nail it down so that I could find out what's going on...

Can you work on that?  And yes, I also suspect a problem in ft2demos's `graph' library.

Werner LEMBERG <wl>
Group administrator
Fri 27 Nov 2015 02:56:14 AM UTC, original submission:  

I see severe artifacts when testing sub-pixel color blending using freetype2 tools like ftstring. I was able to reproduce it in ftview (modified to use cyan-on-red). It shows up occasionally. In the attached images you will see severe color fringes in just a few glyphs. Interestingly it is not always the same glyphs: other glyphs are affected at different sizes.

I suspect this is a bug in tools rather than library. Because the issue is so severe it should have been noticed before.

Alexei Podtelezhnikov <podtelez>
Group Member

 

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Attached Files
file #35573:  BlueFringe.png added by podtelez (71KiB - image/png)
file #35572:  YellowFringe.png added by podtelez (17KiB - image/png)

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -email is unavailable- added by wl (Posted a comment)
  • -email is unavailable- added by podtelez (Submitted the item)
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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2015-11-30 podtelez StatusNone Fixed
        Open/ClosedOpen Closed
    2015-11-27 podtelez Attached File- Added BlueFringe.png, #35573
    2015-11-27 podtelez Attached File- Added YellowFringe.png, #35572

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