[Bug 2001332] New: pango-view with --backend=ft2 and ---antialias=none generates antialiased renderings

https://bugzilla.redhat.com/show_bug.cgi?id=2001332

Bug ID: 2001332
           Summary: pango-view with --backend=ft2 and ---antialias=none
                    generates antialiased renderings
           Product: Fedora
           Version: 34
          Hardware: x86_64
                OS: Linux
            Status: NEW
         Component: pango
          Severity: high
          Assignee: [e-mail]
          Reporter: [e-mail]
        QA Contact: [e-mail]
                CC: [e-mail],
                    [e-mail],
                    [e-mail],
                    [e-mail], [e-mail],
                    [e-mail], [e-mail],
                    [e-mail], [e-mail],
                    [e-mail]
  Target Milestone: ---
    Classification: Fedora

Created attachment 1820649
  --> https://bugzilla.redhat.com/attachment.cgi?id=1820649&action=edit
image showing the problem

Description of problem:

Hello Fedora Team,

I have a recently updated Fedora 34 installation.

The problem I want to report is that it looks like
the pango-view tool is always turning antialiasing on
when one uses the FreeType backend --backend=ft2,
even when one explicitly switches antialiasing off with --antialias=none,
whereas it works for the --backend=cairo option.

A second question would be if the FreeType backend
generally doesn't/can't support --antialias=none?
I tried to find some examples in C with antialising turned off
but I wasn't successful.

I must confess I didn't check other distributions.

As pango-view is regarded as a tool for creating minimal reproducers
against the font rendering stack, I dare to set the severity to 'high' :-)

Best Regards
Andre

Version-Release number of selected component (if applicable):

$ uname -a
Linux localhost.localdomain 5.13.13-200.fc34.x86_64 #1 SMP Thu Aug 26 17:06:39
UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

$ dnf list installed | grep dejavu
dejavu-lgc-sans-fonts.noarch                2.37-16.fc34                       
@fedora
dejavu-lgc-sans-mono-fonts.noarch           2.37-16.fc34                       
@fedora
dejavu-lgc-serif-fonts.noarch               2.37-16.fc34                       
@fedora
dejavu-sans-fonts.noarch                    2.37-16.fc34                       
@fedora
dejavu-sans-mono-fonts.noarch               2.37-16.fc34                       
@fedora
dejavu-serif-fonts.noarch                   2.37-16.fc34                       
@fedora

$ dnf list installed | grep ImageMagick
ImageMagick.x86_64                          1:6.9.11.27-3.fc34                 
@fedora
ImageMagick-libs.x86_64                     1:6.9.11.27-3.fc34                 
@fedora

$ dnf list installed | grep pango
pango.i686                                  1.48.9-2.fc34                      
@updates
pango.x86_64                                1.48.9-2.fc34                      
@updates
pango-devel.x86_64                          1.48.9-2.fc34                      
@updates
pangomm.x86_64                              2.46.1-1.fc34                      
@updates

$ dnf list installed | grep freetype
freetype.i686                               2.10.4-3.fc34                      
@fedora
freetype.x86_64                             2.10.4-3.fc34                      
@fedora
freetype-devel.x86_64                       2.10.4-3.fc34                      
@fedora

$ dnf list installed | grep fontconfig
fontconfig.i686                             2.13.94-2.fc34                     
@updates
fontconfig.x86_64                           2.13.94-2.fc34                     
@updates
fontconfig-devel.x86_64                     2.13.94-2.fc34                     
@updates

$ dnf list installed | grep cairo
cairo.i686                                  1.17.4-3.fc34                      
@fedora
cairo.x86_64                                1.17.4-3.fc34                      
@fedora
cairo-devel.x86_64                          1.17.4-3.fc34                      
@fedora
cairo-gobject.i686                          1.17.4-3.fc34                      
@fedora
cairo-gobject.x86_64                        1.17.4-3.fc34                      
@fedora
cairomm.x86_64                              1.14.2-8.fc34                      
@fedora
python2-cairo.x86_64                        1.18.2-8.fc34                      
@fedora
python3-cairo.x86_64                        1.20.0-2.fc34                      
@fedora

How reproducible:

Always

Steps to Reproduce:

$ pango-view --no-display --dpi=72 --backend=cairo --antialias=none
--font="DejaVu Sans 38" --text="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
--output=abc-cairo-aa-none.png
$ pango-view --no-display --dpi=72 --backend=cairo --antialias=gray
--font="DejaVu Sans 38" --text="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
--output=abc-cairo-aa-gray.png
$ pango-view --no-display --dpi=72 --backend=cairo --antialias=subpixel
--font="DejaVu Sans 38" --text="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
--output=abc-cairo-aa-subpixel.png
$ pango-view --no-display --dpi=72 --backend=ft2 --antialias=none
--font="DejaVu Sans 38" --text="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
--output=abc-ft2-aa-none.png
$ pango-view --no-display --dpi=72 --backend=ft2 --antialias=gray
--font="DejaVu Sans 38" --text="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
--output=abc-ft2-aa-gray.png
$ pango-view --no-display --dpi=72 --backend=ft2 --antialias=subpixel
--font="DejaVu Sans 38" --text="ABCDEFGHIJKLMNOPQRSTUVWXYZ"
--output=abc-ft2-aa-subpixel.png

$ gimp abc-*.png

Actual results:
Attached pngs.
The file abc-ft2-aa-none.png is in gray-scale and not as expected in
black-white.
The file abc-cairo-aa-none.png is in black-white as expected.

Expected results:
I would have expected the files abc*--aa-none.png looking near identical.

Additional info: