在C ++中从头开始创建DirectDraw Surface

Question

I'm trying to convert a 2d array to a DDS and saving it to a file. Array is full of Color structs (each having a red, green, blue and alpha component). Once I get the array to the correct format, I'm sure the saving it to file part won't be a problem.

I'm fine with either using a lib for this (as long as its license allows me to use it in a closed source project and works on both Linux and Windows) or doing it manually, if I can find a nice resource explaining how to do it.

If anyone can point me in the right direction, I'd really appreciate it.

Answer 1

In DirectDraw you can create a surface from the data in memory, by setting up certain fields in the DDSURFACEDESC structure and passing it to the CreateSurface method of the IDirectDraw interface.

First you need to tell DirectDraw which fields of the DDSURFACEDESC structure contain the correct information by setting the dwFlags field to the following set of flags: DDSD_WIDTH | DDSD_HEIGHT | DDSD_PIXELFORMAT | DDSD_LPSURFACE | DDSD_PITCH DDSD_WIDTH | DDSD_HEIGHT | DDSD_PIXELFORMAT | DDSD_LPSURFACE | DDSD_PITCH DDSD_WIDTH | DDSD_HEIGHT | DDSD_PIXELFORMAT | DDSD_LPSURFACE | DDSD_PITCH .

Oh, and this only works for system-memory surfaces, so it's probably needed to add the DDSCAPS_SYSTEMMEMORY flag in the ddsCaps.dwCaps field (if DirectDraw won't do it by default).

Then you specify the address of the beginning of your pixel data array in the lpSurface field. If your buffer is continuous, just set the lPitch to 0. Else you set the correct pitch there (the distance in bytes between the beginnings of two subsequent scanlines).

Set the correct pixel format in ddpfPixelFormat field, with correct bit depth in dwRGBBitCount and RGB masks in dwRBitMask , dwGBitMask and dwBBitMask .

Then set the lXPitch to the number of bytes your pixel has (3 for RGB). It depends on the pixel format you use.

Then pass the filled structure into CreateSurface and see if it works.

When you create the surface this way, keep in mind that DirectDraw will not manage its data buffer himself, and won't free this memory once you call Release on your surface. You need to free this memory yourself when it's no longer used by the surface.

If you want this pixel data to be placed in video memory, on the other hand, you need to create an offscreen surface in a usual way and then lock it, copy your pixels to its own buffer in video memory (you'll find its address in the lpSurface field, and remember to take lPitch in count!), and then unlock it.