How To Get File In Assets From Android NDK

You can read the image from an asset with AAssetManager_open & AAsset_read, but since asset lies in apk you can't get a file path name for it - it is also compressed there. You can save the data to a file and read from that file later or you can directly process the chunk you got from your asset file if OSG allows.

From here:

AAssetDir* assetDir = AAssetManager_openDir(mgr, "");
const char* filename = (const char*)NULL;
while ((filename = AAssetDir_getNextFileName(assetDir)) != NULL) {
    AAsset* asset = AAssetManager_open(mgr, filename, AASSET_MODE_STREAMING);
    char buf[BUFSIZ];
    int nb_read = 0;
    FILE* out = fopen(filename, "w");
    while ((nb_read = AAsset_read(asset, buf, BUFSIZ)) > 0)
        fwrite(buf, nb_read, 1, out);
    fclose(out);
    AAsset_close(asset);
}
AAssetDir_close(assetDir);

One more thing worth mentioning is that android puts restriction on asset size that can be read at time, to 1Mb. In case your file is bigger than that, you have to split it into chunks. Here is my working solution which loads file in chunks to vector of chars:

AAssetManager * mgr = app->activity->assetManager; 
AAssetDir* assetDir = AAssetManager_openDir(mgr, "");

const char* filename;
std::vector<char> buffer;

while ((filename = AAssetDir_getNextFileName(assetDir)) != NULL) 
{
    //search for desired file
    if(!strcmp(filename, /* searched file name */)) 
    {
        AAsset *asset = AAssetManager_open(mgr, filename, AASSET_MODE_STREAMING);

        //holds size of searched file
        off64_t length = AAsset_getLength64(asset);
        //keeps track of remaining bytes to read
        off64_t remaining = AAsset_getRemainingLength64(asset);
        size_t Mb = 1000 *1024; // 1Mb is maximum chunk size for compressed assets
        size_t currChunk;
        buffer.reserve(length);

        //while we have still some data to read
        while (remaining != 0) 
        {
            //set proper size for our next chunk
            if(remaining >= Mb)
            {
                currChunk = Mb;
            }
            else
            {
                currChunk = remaining;
            }
            char chunk[currChunk];

            //read data chunk
            if(AAsset_read(asset, chunk, currChunk) > 0) // returns less than 0 on error
            {
                //and append it to our vector
                buffer.insert(buffer.end(),chunk, chunk + currChunk);
                remaining = AAsset_getRemainingLength64(asset);
            }
        }
        AAsset_close(asset);
    }

}