Problem trying to convert a JPG to PNG and add an alpha mask

[mrBlaQ]

I'm trying to convert a JPG to a PNG and add an alpha mask. Here's the code I have currently. My script dies during MagickSetImageAlphaChannel and error_reporting(E_ALL) doesn't say why.

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            MagickSetImageFormat($wnd, "PNG32");
            error_log("MagickSetImageFormat", 0);
            MagickSetImageAlphaChannel($wnd, MW_ActivateAlphaChannel);
            error_log("MagickSetImageAlphaChannel", 0);
            MagickEvaluateImage($wnd, MW_DivideEvaluateOperator, (100/$alpha), MW_AlphaChannel);
            error_log("MagickEvaluateImage", 0);

My php error log only reports the following, it never makes it to MagickEvaluateImage():

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[Tue Feb 19 16:57:17 2008] [error] [client 208.42.140.15] MagickCropImage
[Tue Feb 19 16:57:17 2008] [error] [client 208.42.140.15] MagickSetImageFormat

Can anyone provide some insight on the proper way to accomplish this task?

Thanks,
Dave

[mrBlaQ]

I needed to add...

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MagickSetImageType($wnd, MW_TrueColorMatteType);

Before my MagickEvaluateImage() function.