Is there a way to know original image was RGB vs RGBA? about astc-encoder HOT 4 CLOSED

No, this isn't possible via something simple like a header look up. The color endpoint format may vary on a per-block basis in the compressed data, so to determine this you'd have to read the entire file and decode all blocks.

from astc-encoder.

Yeah, parsing all the endpoints is what i ended up doing. Slows down loading of the file, but then i at least have the information i need. please keep this need in mind when designing future iterations of this format or other formats in the future.

from astc-encoder.

use KTX container format instead. here's astc header:

typedef struct __attribute__((packed))
{
    uint8_t magic[4];
    uint8_t blockDimX;
    uint8_t blockDimY;
    uint8_t blockDimZ;
    uint8_t xSize[3];
    uint8_t ySize[3];
    uint8_t zSize[3];
} astc_header;

and here's ktx header:

typedef struct __attribute__((packed))
{
    uint8_t identifier[12];
    uint32_t endianness;
    uint32_t glType;
    uint32_t glTypeSize;
    uint32_t glFormat;
    uint32_t glInternalFormat;
    uint32_t glBaseInternalFormat;
    uint32_t pixelWidth;
    uint32_t pixelHeight;
    uint32_t pixelDepth;
    uint32_t arrayElementCount;
    uint32_t faceCount;
    uint32_t mipmapLevelCount;
    uint32_t keyValueDataLength;
} ktx_header;

Note, astc is an encoding, also is a file format.
KTX is a container format it can contains various of pixel format such as astc.
you can use ktx container to store astc content. original format is in it's header (glFormat , glInternalFormat , glBaseInternalFormat )

from astc-encoder.

Closing - original question was answered.

from astc-encoder.