Using the call '&' operator with multiple parameters - powershell

Question

$sImageMagickHome = "C:\ImageMagick"
$sImageMagickConv = "$sImageMagickHome\convert.exe"
$sImageMagickArgs = #( '--%',
'-background transparent',
'-fill hsb(0,0,0)',
'-font Arial',
'-pointsize 18',
'-size 18x26',
'-gravity center')
for ( $i = 0x01; $i -le 0x05; $i++ )
{
$y = [char]$i
& $sImageMagickConv $sImageMagickArgs label:$y $sCharsDir\$y.png
#Write-Host $sImageMagickConv $sImageMagickArgs label:$y $sCharsDir\$y.png
}
Using Write-Host I can get an example to copy paste into the command line and I find it does run correctly if I run this single line from the PowerShell prompt:
C:\ImageMagick\convert.exe --% -background transparent -fill hsb(0,0,0) -font Arial -pointsize 18 -size 18x26 -gravity center label:☺ C:\Users\erics_000\Desktop\Output\Chars\☺.png
Using the call operator '&' from inside the script does not work at all however and leads to some error messages:
convert.exe: UnableToOpenBlob `--%': No such file or directory # error/blob.c/OpenBlob/2697.
convert.exe: NoDecodeDelegateForThisImageFormat `' # error/constitute.c/ReadImage/501.
convert.exe: UnrecognizedOption `-background transparent' # error/convert.c/ConvertImageCommand/858.
The article I have been reading is:
http://social.technet.microsoft.com/wiki/contents/articles/7703.powershell-running-executables.aspx
Thank you...

Answer 1

The following script works for me:
$sImageMagickHome = "C:\dev\im"
$sImageMagickConv = "$sImageMagickHome\convert.exe"
$sImageMagickArgs = #('-background', 'transparent',
'-fill', 'hsb(0,0,0)',
'-font', 'Arial',
'-pointsize', '18',
'-size', '18x26',
'-gravity', 'center')
for ( $i = 65; $i -le 67; $i++ )
{
$y = [char]$i
& $sImageMagickConv $sImageMagickArgs label:$y c:\dev\$y.bmp
}
Note that you cannot just Write-Host the arguments and try running it from command line, Powershell does special processing for & operator (adds quotes where needed), which it does not when you pass same arguments to Write-Host.
You'd probably want to install PSCX and play around with echoargs utility bundled with it to gain better understanding of how arguments are passed.