lg_dds_loader.c File Reference

Functions
void *	lg_load_dds (const char *path, lg_tc_format *tc_format, size_t *size, int *w, int *h, int *n_mipmaps)

Detailed Description

 === Loading of DDS (DXT1 and DXT3) compressed textures on Linux and Win32 ===

Function Documentation

lg_load_dds()

void* lg_load_dds	(	const char *	path,
		lg_tc_format *	tc_format,
		size_t *	size,
		int *	w,
		int *	h,
		int *	n_mipmaps
	)

Load a DDS (DXT1 and DXT3 formats) compressed texture

Returned data must be freed afterwards

 Linux: S3TC (DDS files with DXT1/3 compression format)     ->      GL_EXT_texture_compression_s3tc
    DXT1:   8:1 compression ratio
            4x4 pixels block -> 64 bits = 8 bytes
    DXT3:   4:1 compression ratio
            4x4 pixels block -> 128 bits = 16 bytes

 (https://learn.microsoft.com/en-us/windows/win32/direct3ddds/dx-graphics-dds-pguide#dds-file-layout)
 DDS = DirectDrawSurface

 === DDS layout ===

    uint32_t        dds_magic;      // -> 'DDS ' (0x20534444)
    DDS_Header      header;
    void            *data;
    void            *data2;

 (No DDS_Header_dxt10 header10)

 sizeof(magic) + sizeof(DDS_Header) = 128

 See: lg_dds_loader.h

 To create DDS DXT1/DXT3 files using nvidia tex tools:
            - without mipmpas
            nvcompress -bc1 -noalpha -nomips -production wallpaper1_1024x512.png wallpaper1_1024x512_dxt1.dds
            - without mipmpas
            nvcompress -bc2 -nomips -production wallpaper1_1024x512.png wallpaper1_1024x512_dxt3.dds
            - with mipmpas
            nvcompress -bc2 -production wallpaper1_1024x512.png wallpaper1_1024x512_w_mips_dxt3.dds

 (https://developer.nvidia.com/gpu-accelerated-texture-compression)

Parameters

path
tc_format	Pointer to lg_tc_format which will store compressed texture format
size	Pointer to size_t which will store compressed texture size (cumulative size, ie of all levels, but excluding magic and header)
w	Pointer to int which will store width (of level 0)
h	Pointer to int which will store height (of level 0)
n_mipmaps	Pointer to int which will store number of generated mipmaps

Returns

Pointer to compressed texture data if OK, NULL on error