title: How to check if the PNG image loaded into FMX.TBitmap has an alpha channel?
body: <p>I'm loading PNG images into <code>FMX.Type.TBitmap</code> in Delphi-XE2 Update3 FireMonkey HD application. How do I check if loaded PNG image has an alpha channel or not?</p>
  
  <p>Currently if I load an image with an alpha channel it has alpha info in <code>Bitmap.Scanline[Y]^[X]</code> in a form of $AABBGGRR. However if I load PNG image without alpha the said record has only $00BBGGRR entries (AA = 0), just like an image with clear alpha. Hence the problem - how to determine if it is RGBA image with the alpha fully transparent or it is a RGB image (in this case I will process it to make the alpha fully opaque). Note: Checking through all pixels is not an option.</p>
  
  <p>FMX TBitmap has no <code>PixelFormat</code> property, nor I could find <code>HasAlpha</code> flag.</p>