@echo off
 
set ImageMagickDir=C:\Program Files\ImageMagick-6.7.5-Q16
set IMConvert="%ImageMagickDir%\convert.exe"
set IMMogrify="%ImageMagickDir%\mogrify.exe"
 
set PrimaryImage=1920x1200\00.png
set SecondaryImage=1600x900\00.png
set OutputImage=Wallpaper.jpg
 
set SecondaryImageSize=1600x1920
rem This value should be 900 - y offset in Display Properties -> Settings, display 2.
set SecondaryImageOffset=+772
rem 128

rem goto skip
 
rename 1600x900\00.png x.png
rename 1600x900\01.png 00.png
rename 1600x900\02.png 01.png
...
rename 1600x900\46.png 45.png
rename 1600x900\47.png 46.png
rename 1600x900\x.png 47.png
 
rename 1920x1200\00.png x.png
rename 1920x1200\01.png 00.png
rename 1920x1200\02.png 01.png
...
rename 1920x1200\48.png 47.png
rename 1920x1200\49.png 48.png
rename 1920x1200\x.png 49.png
 
:skip

rem Convert "(" %PrimaryImage% ")" "(" "(" %SecondaryImage% -rotate -90 ")" "(" %SecondaryImage% -rotate -90 ")" -append -crop %SecondaryImageSize%+0%SecondaryImageOffset% +repage ")" +append %OutputImage%
 
Convert "(" %PrimaryImage% +repage ")" "(" "(" %SecondaryImage% +repage ")" "(" %SecondaryImage% +repage ")" -append -crop %SecondaryImageSize%+0%SecondaryImageOffset% +repage ")" +append %OutputImage%
pause