/// <summary>
/// Create a compatible memory HDC from the given HDC.<br/>
/// The memory HDC can be rendered into without effecting the original HDC.<br/>
/// The returned memory HDC and <paramref name="dib"/> must be released using <see cref="ReleaseMemoryHdc"/>.
/// </summary>
/// <param name="hdc">the HDC to create memory HDC from</param>
/// <param name="width">the width of the memory HDC to create</param>
/// <param name="height">the height of the memory HDC to create</param>
/// <param name="dib">returns used bitmap memory section that must be released when done with memory HDC</param>
/// <returns>memory HDC</returns>
public static IntPtr CreateMemoryHdc(IntPtr hdc, int width, int height, out IntPtr dib)
{
// Create a memory DC so we can work off-screen
IntPtr memoryHdc = CreateCompatibleDC(hdc);
SetBkMode(memoryHdc, 1);
// Create a device-independent bitmap and select it into our DC
var info = new BitMapInfo();
info.biSize = Marshal.SizeOf(info);
info.biWidth = width;
info.biHeight = -height;
info.biPlanes = 1;
info.biBitCount = 32;
info.biCompression = 0; // BI_RGB
IntPtr ppvBits;
dib = CreateDIBSection(hdc, ref info, 0, out ppvBits, IntPtr.Zero, 0);
SelectObject(memoryHdc, dib);
return memoryHdc;
}
/// <summary>
/// Create a compatible memory HDC from the given HDC.<br/>
/// The memory HDC can be rendered into without effecting the original HDC.<br/>
/// The returned memory HDC and <paramref name="dib"/> must be released using <see cref="ReleaseMemoryHdc"/>.
/// </summary>
/// <param name="hdc">the HDC to create memory HDC from</param>
/// <param name="width">the width of the memory HDC to create</param>
/// <param name="height">the height of the memory HDC to create</param>
/// <param name="dib">returns used bitmap memory section that must be released when done with memory HDC</param>
/// <returns>memory HDC</returns>
public static IntPtr CreateMemoryHdc(IntPtr hdc, int width, int height, out IntPtr dib)
{
// Create a memory DC so we can work off-screen
IntPtr memoryHdc = CreateCompatibleDC(hdc);
SetBkMode(memoryHdc, 1);
// Create a device-independent bitmap and select it into our DC
var info = new BitMapInfo();
info.biSize = Marshal.SizeOf(info);
info.biWidth = width;
info.biHeight = -height;
info.biPlanes = 1;
info.biBitCount = 32;
info.biCompression = 0; // BI_RGB
IntPtr ppvBits;
dib = CreateDIBSection(hdc, ref info, 0, out ppvBits, IntPtr.Zero, 0);
SelectObject(memoryHdc, dib);
return(memoryHdc);
}
public static extern IntPtr CreateDIBSection(IntPtr hdc, [In] ref BitMapInfo pbmi, uint iUsage, out IntPtr ppvBits, IntPtr hSection, uint dwOffset);