Get size of layered PSD file ?

[nsh]

Hi, i'm trying to get the width and height out of a PSD file, but only get size of one layer.

I'm trying to do this with this code:

magick_merged_wand=NewMagickWand();
magick_merged_wand=MagickMergeImageLayers(magick_wand,MergeLayer);
*width = MagickGetImageWidth(magick_merged_wand);
*height = MagickGetImageHeight(magick_merged_wand);

The org image is 1280 x 720 pxl, but i get 615 x 77 (the size of one Layer)

[nsh]

using MosaicLayer as method,is better, but still returns not the exact size of the org image

magick_merged_wand=MagickMergeImageLayers(magick_wand,MosaicLayer);
*width = MagickGetImageWidth(magick_merged_wand);
*height = MagickGetImageHeight(magick_merged_wand);