"-distort resize" followed by "-flatten" causes a strange 2px border

[sas]

This command:

Code: Select all

convert  netscape:  -distort resize 100x100!  -flatten  x.png

Results in this image for me:

Note the image size of 102x102, and a 2px green border on the bottom and right egde.

When I run the same command with "-resize" instead of "-distort resize", I get a 100x100 image without border:


I would have expected both commands to produce a 100x100 image without border.
Why is -distort resize behaving differently, and how can I prevent it?
(I prefer to use -distort resize because of the better result quality, especially when upscaling.)

ImageMagick version: 6.9.2-6 Q16 x86_64 2015-12-06, on Linux.

[magick]

Remove the virtual canvas:

• convert netscape: -distort resize 100x100! +repage -flatten x.png

[sas]

That seems to work in my case, thanks!

I'm still a little worried about the "-distort resize" behavior though, since I don't understand why it happens.

[magick]

The extra pixels come from the -flatten option, not -distort. The -flatten option respects any virtual canvas.

[sas]

But "-distort" is responsible for extending the virtual canvas in this strange way, isn't it?
Is it supposed to do that?

[magick]

The -distort resize option is a special case for distort, it does not extend the virtual canvas.

[fmw42]

.
I believe there is a problem with -distort resize. The resulting image virtual canvas is indeed 102x102+0+0 rather than 100x100+0+0.

Code: Select all

convert  netscape:  -distort resize 100x100! tmp.png
Fred-Weinhauss-Mac-mini:desktop fred$ identify -verbose tmp.png
Image: tmp.png
   Geometry: 100x100+0+0
...
  Page geometry: 102x102+0+0
 ...
 

[magick]

We can reproduce the problem you posted and have a patch in ImageMagick 6.9.2-10 Beta, available by sometime tomorrow. Thanks.

[sas]

Good to know, thanks!