soil.lua

local ffi = require "ffi"
soil = soil or {}

-- SOIL DDS loader
-- FFI bindings by swyter :)
ffi.cdef[[
/**
	The format of images that may be loaded (force_channels).
	SOIL_LOAD_AUTO leaves the image in whatever format it was found.
	SOIL_LOAD_L forces the image to load as Luminous (greyscale)
	SOIL_LOAD_LA forces the image to load as Luminous with Alpha
	SOIL_LOAD_RGB forces the image to load as Red Green Blue
	SOIL_LOAD_RGBA forces the image to load as Red Green Blue Alpha
**/
enum
{
	SOIL_LOAD_AUTO = 0,
	SOIL_LOAD_L = 1,
	SOIL_LOAD_LA = 2,
	SOIL_LOAD_RGB = 3,
	SOIL_LOAD_RGBA = 4
};

/**
	Passed in as reuse_texture_ID, will cause SOIL to
	register a new texture ID using glGenTextures().
	If the value passed into reuse_texture_ID > 0 then
	SOIL will just re-use that texture ID (great for
	reloading image assets in-game!)
**/
enum
{
	SOIL_CREATE_NEW_ID = 0
};


/**
	flags you can pass into SOIL_load_OGL_texture()
	and SOIL_create_OGL_texture().
	(note that if SOIL_FLAG_DDS_LOAD_DIRECT is used
	the rest of the flags with the exception of
	SOIL_FLAG_TEXTURE_REPEATS will be ignored while
	loading already-compressed DDS files.)

	SOIL_FLAG_POWER_OF_TWO: force the image to be POT
	SOIL_FLAG_MIPMAPS: generate mipmaps for the texture
	SOIL_FLAG_TEXTURE_REPEATS: otherwise will clamp
	SOIL_FLAG_MULTIPLY_ALPHA: for using (GL_ONE,GL_ONE_MINUS_SRC_ALPHA) blending
	SOIL_FLAG_INVERT_Y: flip the image vertically
	SOIL_FLAG_COMPRESS_TO_DXT: if the card can display them, will convert RGB to DXT1, RGBA to DXT5
	SOIL_FLAG_DDS_LOAD_DIRECT: will load DDS files directly without _ANY_ additional processing
	SOIL_FLAG_NTSC_SAFE_RGB: clamps RGB components to the range [16,235]
	SOIL_FLAG_CoCg_Y: Google YCoCg; RGB=>CoYCg, RGBA=>CoCgAY
	SOIL_FLAG_TEXTURE_RECTANGE: uses ARB_texture_rectangle ; pixel indexed & no repeat or MIPmaps or cubemaps
**/
enum
{
	SOIL_FLAG_POWER_OF_TWO = 1,
	SOIL_FLAG_MIPMAPS = 2,
	SOIL_FLAG_TEXTURE_REPEATS = 4,
	SOIL_FLAG_MULTIPLY_ALPHA = 8,
	SOIL_FLAG_INVERT_Y = 16,
	SOIL_FLAG_COMPRESS_TO_DXT = 32,
	SOIL_FLAG_DDS_LOAD_DIRECT = 64,
	SOIL_FLAG_NTSC_SAFE_RGB = 128,
	SOIL_FLAG_CoCg_Y = 256,
	SOIL_FLAG_TEXTURE_RECTANGLE = 512
};

/**
	Loads an image from disk into an OpenGL texture.
	\param filename the name of the file to upload as a texture
	\param force_channels 0-image format, 1-luminous, 2-luminous/alpha, 3-RGB, 4-RGBA
	\param reuse_texture_ID 0-generate a new texture ID, otherwise reuse the texture ID (overwriting the old texture)
	\param flags can be any of SOIL_FLAG_POWER_OF_TWO | SOIL_FLAG_MIPMAPS | SOIL_FLAG_TEXTURE_REPEATS | SOIL_FLAG_MULTIPLY_ALPHA | SOIL_FLAG_INVERT_Y | SOIL_FLAG_COMPRESS_TO_DXT | SOIL_FLAG_DDS_LOAD_DIRECT
	\return 0-failed, otherwise returns the OpenGL texture handle
**/
	unsigned int
	SOIL_load_OGL_texture
	(
		const char *filename,
		int force_channels,
		unsigned int reuse_texture_ID,
		unsigned int flags
	);
	
]]
soilffi = ffi.load("soil")


if soilffi then
	--- Loads an image file to a texture, using SOIL
	-- @param filepath Path to file to load texture from / DDS-DXT1-3-5 / PNG / BMP / JPG / TGA / ...
	-- @return Texture ID
	function soil.loadTexture(filepath)

		local image = soilffi.SOIL_load_OGL_texture(filepath, soilffi.SOIL_LOAD_AUTO, soilffi.SOIL_CREATE_NEW_ID, soilffi.SOIL_FLAG_MIPMAPS+soilffi.SOIL_FLAG_TEXTURE_REPEATS+soilffi.SOIL_FLAG_INVERT_Y)
		
		if image == 0 then
			error("SOIL DDS failed")
		else
			print("SOIL DDS created a new texture with handle "..image)
		end
		
		return image
	end
end