dim Current as PictureMBS // your picture
dim f as FolderItem

f=GetsaveFolderItem(FileTypes.Png,"test.png")

if f<>Nil then
  const PNG_COLOR_MASK_PALETTE   = 1
  const PNG_COLOR_MASK_COLOR     = 2
  const PNG_COLOR_MASK_ALPHA     = 4
  
  dim p as new PNGWriterMBS
  
  p.Width=Current.Width
  p.Height=Current.Height
  p.Type=PNG_COLOR_MASK_COLOR
  p.bpc=3
  p.Rowbytes=p.Width*p.bpc
  
  if p.OpenWriteDestination(f) then
    if p.SetHeader(false, -1) then
      if p.SetGamma(0) then
        if p.WriteInfo then
          dim i,c as integer
          
          c=p.Height-1
          for i=0 to c
            p.WriteRow current.RowInFormat(i, Current.ImageFormatRGB)
          next
          
          if p.WriteEnd then
            MsgBox "OK"
          end if
        end if
      end if
    end if
  end if
end if