Function ILAPIENTRY ilNVidiaCompressDXT

DevIL/src-IL/src/il_nvidia.cpp:85–136

Compresses data to a DXT format using nVidia's Texture Tools library. The data must be in unsigned byte RGBA format. The alpha channel will be ignored if DxtType is IL_DXT1. DxtSize is used to return the size in bytes of the DXTC data returned.

//  The data must be in unsigned byte RGBA format.  The alpha channel will be ignored if DxtType is IL_DXT1.
//  DxtSize is used to return the size in bytes of the DXTC data returned.
ILAPI ILubyte* ILAPIENTRY ilNVidiaCompressDXT(ILubyte *Data, ILuint Width, ILuint Height, ILuint Depth, ILenum DxtFormat, ILuint *DxtSize)
{
	if (Data == NULL) {  // We cannot operate on a null pointer.
		ilSetError(IL_INVALID_PARAM);
		return NULL;
	}

	// The nVidia Texture Tools library does not support volume textures yet.
	if (Depth != 1) {
		ilSetError(IL_INVALID_PARAM);
		return NULL;
	}

	InputOptions inputOptions;
	inputOptions.setTextureLayout(TextureType_2D, Width, Height);
	inputOptions.setMipmapData(Data, Width, Height);
	inputOptions.setMipmapGeneration(false, -1);  //@TODO: Use this in certain cases.

	OutputOptions outputOptions;
	ilOutputHandlerMem outputHandler(Width, Height, DxtFormat);
	outputOptions.setOutputHeader(false);
	outputOptions.setOutputHandler(&outputHandler);

	if (outputHandler.NewData == NULL)
		return NULL;

	CompressionOptions compressionOptions;
	switch (DxtFormat)
	{
		case IL_DXT1:
			compressionOptions.setFormat(Format_DXT1);
			break;
		case IL_DXT1A:
			compressionOptions.setFormat(Format_DXT1a);
			break;
		case IL_DXT3:
			compressionOptions.setFormat(Format_DXT1);
			break;
		case IL_DXT5:
			compressionOptions.setFormat(Format_DXT5);
			break;
		default:  // Does not support DXT2 or DXT4.
			ilSetError(IL_INVALID_PARAM);
			break;
	}

	Compressor compressor;
	compressor.process(inputOptions, compressionOptions, outputOptions);

	*DxtSize = outputHandler.Size;
	return outputHandler.NewData;
}