此图像格式为“PNG”ImageMagick CentOS无解码委托

I'm trying to use ImageMagick in CentOS to generate pdf documents and convert PNG images. ImageMagic is already installed and imagic extension is loaded and working in PHP 5.5 but when I try to generate PDF or convert images I get the follow error: no decode delegate for this image format `PNG'

I've already installed libpng and reinstalled ImageMagic but the problem continues