lg_astc_loader.c File Reference

Functions
void *	lg_load_astc (const char *path, lg_tc_format *tc_format, size_t *size, int *w, int *h, int *n_mipmaps)
void *	lg_load_etc1 (const char *path, lg_tc_format *tc_format, size_t *size, int *w, int *h, int *n_mipmaps)

Detailed Description

 === Loading of ASTC and ETC1 compressed textures on Android ===

Function Documentation

lg_load_astc()

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

Load an ASTC compressed texture

Returned data must be freed afterwards

 Android: ASTC      ->      GL_KHR_texture_compression_astc_ldr/hdr
                    GL_EXT_texture_compression_astc_decode_mode
    16 bytes per compressed block
    Not available on all devices

 (https://github.com/ARM-software/astc-encoder/blob/main/Docs/FileFormat.md)

 === ASTC layout ===

    struct  ASTC_Header
    void    *data

 sizeof(ASTC_Header) = 16 bytes

 See: lg_astc_loader.h

 Using ASTC encoder from https://launchpad.net/~roehling/+archive/ubuntu/open3d?field.series_filter=focal
    - Enable PPA
    - Install astenc

    astcenc -cl wallpaper2_1024x512.png wallpaper2_1024x512.astc 4x4 -thorough

 Doc: astcenc -help |less

 If no ASTC support, fallback to ETC1 (available on most devices)

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

lg_load_etc1()

void* lg_load_etc1	(	const char *	path,
		lg_tc_format *	tc_format,
		size_t *	size,
		int *	w,
		int *	h,
		int *	n_mipmaps
	)

Load an ETC1 compressed texture

Fallback if no ASTC support

Returned data must be freed afterwards

 Android: ETC1      ->      GL_OES_compressed_ETC1_RGB8_texture
    6:1 compression ratio
    4x4 pixels block -> 64 bits = 8 bytes
    Container: PKM file, header size = 16
    Available on most devices

 === PKM/ETC1 layout ===

    struct  PKM_Header
    void    *data

 sizeof(PKM_Header) = 16 bytes

 See: lg_astc_loader.h

 To create PKM/ETC1 files:
    etc1tool (in Android SDK)

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