private MemoryStream SaveBitmapToStream(IntPtr pBits)
{
MemoryStream memoryStream = new MemoryStream();
IntPtr hdc = IntPtr.Zero;
IntPtr hPalette = IntPtr.Zero;
try
{
hdc = User32.GetDC(IntPtr.Zero);
if (hdc == IntPtr.Zero)
{
throw new ExternalException("Call to native API (GetDC) failed");
}
// Compute bitmap size and create it if needed
int paletteSize = 0;
IntPtr structBmpInfoPtr = new IntPtr(pBits.ToInt64() + Marshal.OffsetOf(typeof(GDI32.BITMAPINFOHEADER), "biSize").ToInt64());
int structBmpInfoSize = Marshal.ReadInt32(structBmpInfoPtr);
IntPtr bitCountPtr = new IntPtr(pBits.ToInt64() + Marshal.OffsetOf(typeof(GDI32.BITMAPINFOHEADER), "biBitCount").ToInt64());
int bitCount = Marshal.ReadInt32(bitCountPtr);
if (bitCount <= 8)
{
paletteSize = 1 << bitCount;
IntPtr colorUsedPtr = new IntPtr(pBits.ToInt64() + Marshal.OffsetOf(typeof(GDI32.BITMAPINFOHEADER), "biClrUsed").ToInt64());
int colorUsed = Marshal.ReadInt32(colorUsedPtr);
if (colorUsed > 0)
{
paletteSize = colorUsed;
}
paletteSize *= 4; // 4 -> sizeof(RGBQUAD)
// Create palette
IntPtr palettePtr = IntPtr.Zero;
try
{
int structLogPaletteSize = Marshal.SizeOf(typeof(GDI32.LOGPALETTE));
palettePtr = Marshal.AllocHGlobal(structLogPaletteSize + paletteSize);
IntPtr palVersion = new IntPtr(palettePtr.ToInt64() + Marshal.OffsetOf(typeof(GDI32.LOGPALETTE), "palVersion").ToInt64());
IntPtr palNumEntries = new IntPtr(palettePtr.ToInt64() + Marshal.OffsetOf(typeof(GDI32.LOGPALETTE), "palNumEntries").ToInt64());
Marshal.WriteInt16(palVersion, 0x300);
Marshal.WriteInt16(palNumEntries, (short)(paletteSize / 4));
for (int t = 0; t < paletteSize; t += 4)
{
IntPtr pRgbfBits = new IntPtr(pBits.ToInt64() + structBmpInfoSize + t);
IntPtr pRgbfPallette = new IntPtr(palettePtr.ToInt64() + structLogPaletteSize + t);
Marshal.WriteInt32(pRgbfPallette, Marshal.ReadInt32(pRgbfBits)); //
}
hPalette = GDI32.CreatePalette(palettePtr);
if (hPalette == IntPtr.Zero)
{
throw new ExternalException("Call to native API (CreatePalette) failed");
}
}
finally
{
if (palettePtr != IntPtr.Zero)
{
Marshal.FreeHGlobal(palettePtr); palettePtr = IntPtr.Zero;
}
}
}
// Create hBitmap, create Bitmap from it and save as stream
IntPtr offsetToBits = new IntPtr(pBits.ToInt64() + structBmpInfoSize + paletteSize);
IntPtr hBitmap = GDI32.CreateDIBitmap(hdc, pBits, GDI32.CBM_INIT, offsetToBits, pBits, GDI32.DIB_RGB_COLORS);
if (hBitmap == IntPtr.Zero)
{
throw new ExternalException("Call to native API (CreateDIBitmap) failed");
}
using (Bitmap bmp = (hPalette == IntPtr.Zero) ? Bitmap.FromHbitmap(hBitmap) : Bitmap.FromHbitmap(hBitmap, hPalette))
{
bmp.Save(memoryStream, ImageFormat.Png);
}
//
}
finally
{
if (hdc != IntPtr.Zero)
{
User32.ReleaseDC(IntPtr.Zero, hdc); hdc = IntPtr.Zero;
}
if (hPalette != IntPtr.Zero)
{
GDI32.DeleteObject(hPalette); hPalette = IntPtr.Zero;
}
}
return(memoryStream);
}