Question

I’m trying to write an application that converts 48 bit-per-pixel PNG files to a proprietary (Bayer) format.

The code (courtesy here) below works great for some PNG file formats, but when I try a bona fide 48 bit PNG the code throws an exception – is there an alternative?

    static public byte[] BitmapDataFromBitmap(Bitmap objBitmap)     {         MemoryStream ms = new MemoryStream();         objBitmap.Save(ms, ImageFormat.BMP);  // GDI+ exception thrown for > 32 bpp         return (ms.GetBuffer());     }      private void Bayer_Click(object sender, EventArgs e)     {         if (this.pictureName != null)         {             Bitmap bmp = new Bitmap(this.pictureName);             byte[] bmp_raw = BitmapDataFromBitmap(bmp);             int bpp = BitConverter.ToInt32(bmp_raw, 28); // 28 - BMP header defn.              MessageBox.Show(string.Format('Bits per pixel = {0}', bpp));         }     } 

Answer 1

The BMP encoder doesn’t support 48bpp formats. You can get a crack at the pixels with the Bitmap.LockBits() method. Although the MSDN Library article for PixelFormat says that 48bpp is treated like 24bpp images, I do in fact see 6 byte pixels with this code:

  Bitmap bmp = new Bitmap(@'c:\temp\48bpp.png');   BitmapData bd = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height),     ImageLockMode.ReadOnly, PixelFormat.Format48bppRgb);   // Party with bd.Scan0   //...   bmp.UnlockBits(bd);