I am making a 2D game with Direct3D,and use D3DXCreateTextureFromFileInMemoryEx to load my images of game.There are 221KB size of images in my game. But when I use D3DXCreateTextureFromFileInMemoryEx to load the image to memory.They are becoming Dozens of times in the memory of use.
So,how can i to reduce the memory of use?
The D3DX Texture loading functions by default are very accomodating and will try and be helpful by performing all kinds of format conversions, compression / decompression, scaling, mip-map generation and other tasks for you to turn an arbitrary source image into a usable texture.
If you want to prevent any of that conversion (which can be expensive in both CPU cost and memory usage) then you need to ensure that your source textures are already in exactly the format you want and then pass flags to D3DX to tell it not to perform any conversions or scaling.
Generally the only file format that supports all of the texture formats that D3D uses is the D3D format DDS so you will want to save all of your source assets as DDS files. If the software you use to make your textures does not directly support saving DDS files you can use the tools that come with the DirectX SDK to do the conversion for you, write your own tools or use other third party conversion tools.
If you have the full DirectX SDK installed (the June 2010 SDK, the last standalone release) you can use the DirectX Texture Tool which is installed along with it. This isn't shipped with the Windows 8 SDK though (the DirectX SDK is now part of the Windows SDK and doesn't ship as a standalone SDK).
Once you have converted your source assets to DDS files with exactly the format you want to use at runtime (perhaps DXT compressed, with a full mipmap chain pre-generated) you want to pass the right flags to D3DX texture loading functions to avoid any conversions. This means you should pass:
D3DX_DEFAULT_NONPOW2 for the Width and Height parameters and D3DX_DEFAULT for the MipLevels parameter (meaning take the dimensions from the file and don't round the size to a power of 2)*. D3DFMT_FROM_FILE for the Format parameter (meaning use the exact texture format from the file).D3DX_FILTER_NONE for the Filter and MipFilter parameters (meaning don't perform any scaling or filtering).If you pre-process your source assets to be in the exact format you want to use at runtime, save them as DDS files and set all the flags above to tell D3DX not to perform any conversions then you should find your textures load much faster and without excessive memory usage.
*This requires your target hardware supports non power of 2 textures or you only use power of 2 textures. Almost all hardware from the last 5 years supports non power of 2 textures though so this should be pretty safe.
