Extracting icons with imagemagick creates black stripes on transparency

问题

For a project of mine I'm fetching websites favicons and storing them to be displayed in a website. Sounds pretty trivial, but I have one strange issue. Almost all icons come in a .ico format, which is not very web friendly. Some icons also have different sizes in them. I'm using Imagemagick to convert them to PNG and extract only the 16x16 icon.

I'm using the following command line for this:

convert source.ico -geometry 16x16 -alpha on -background none -flatten out.png

Unfortunately on some icons this creates some nasty horizontal black stripes in the transparent areas. Here is an example:

This is the original icon:

http://g.etfv.co/http://www.mysqlperformanceblog.com/

This is the result:

http://img585.imageshack.us/img585/1463/65407408.png

Here it is again embedded here:

What could be wrong here? My ImageMagick is version 6.5.4-7

回答1:

Try updating your Imagemagick installation: I tried your command with your .ico file with version 6.6.0-1 and it created the png file correctly

Version: ImageMagick 6.6.0-1 2010-03-03 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP

来源：https://stackoverflow.com/questions/16733545/extracting-icons-with-imagemagick-creates-black-stripes-on-transparency