internal static extern IntPtr CreateDIBSection(
IntPtr hdc,
ref NativeStructs.BITMAPINFO pbmi,
uint iUsage,
out IntPtr ppvBits,
IntPtr hSection,
uint dwOffset);
/// <summary>
/// Allocates a bitmap of the given height and width. Pixel data may be read/written directly,
/// and it may be drawn to the screen using PdnGraphics.DrawBitmap().
/// </summary>
/// <param name="width">The width of the bitmap to allocate.</param>
/// <param name="height">The height of the bitmap to allocate.</param>
/// <param name="handle">Receives a handle to the bitmap.</param>
/// <returns>A pointer to the bitmap's pixel data.</returns>
/// <remarks>
/// The following invariants may be useful for implementors:
/// * The bitmap is always 32-bits per pixel, BGRA.
/// * Stride for the bitmap is always width * 4.
/// * The upper-left pixel of the bitmap (0,0) is located at the first memory location pointed to by the returned pointer.
/// * The bitmap is top-down ("memory correct" ordering).
/// * The 'handle' may be any type of data you want, but must be unique for the lifetime of the bitmap, and must not be IntPtr.Zero.
/// * The handle's value must be understanded by PdnGraphics.DrawBitmap().
/// * The bitmap is always modified by directly reading and writing to the memory pointed to by the return value.
/// * PdnGraphics.DrawBitmap() must always render from this memory location (i.e. it must treat the memory as 'volatile')
/// </remarks>
public static IntPtr AllocateBitmap(int width, int height, out IntPtr handle)
{
NativeStructs.BITMAPINFO bmi = new NativeStructs.BITMAPINFO();
bmi.bmiHeader.biSize = (uint)sizeof(NativeStructs.BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = width;
bmi.bmiHeader.biHeight = -height;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = NativeConstants.BI_RGB;
bmi.bmiHeader.biSizeImage = 0;
bmi.bmiHeader.biXPelsPerMeter = 96;
bmi.bmiHeader.biYPelsPerMeter = 96;
bmi.bmiHeader.biClrUsed = 0;
bmi.bmiHeader.biClrImportant = 0;
IntPtr pvBits;
IntPtr hBitmap = SafeNativeMethods.CreateDIBSection(
IntPtr.Zero,
ref bmi,
NativeConstants.DIB_RGB_COLORS,
out pvBits,
IntPtr.Zero,
0);
if (hBitmap == IntPtr.Zero)
{
throw new OutOfMemoryException("CreateDIBSection returned NULL (" + Marshal.GetLastWin32Error().ToString() + ") while attempting to allocate " + width + "x" + height + " bitmap");
}
handle = hBitmap;
long bytes = (long)width * (long)height * 4;
if (bytes > 0)
{
GC.AddMemoryPressure(bytes);
}
return(pvBits);
}