load extra from png.c

static void ccv_convnet_read_extra(ccv_convnet_t* convnet, const char* filename)
{
	sqlite3* db = 0;
	if (SQLITE_OK == sqlite3_open(filename, &db))
	{
		sqlite3_stmt* layer_quant_stmt = 0;
		const char layer_quant_qs[] =
			"SELECT layer, quant FROM layer_quant;";
		if (SQLITE_OK == sqlite3_prepare_v2(db, layer_quant_qs, sizeof(layer_quant_qs), &layer_quant_stmt, 0))
		{
			while (sqlite3_step(layer_quant_stmt) == SQLITE_ROW)
			{
				ccv_convnet_layer_t* layer = convnet->layers + sqlite3_column_int(layer_quant_stmt, 0);
				int qnum = sqlite3_column_bytes(layer_quant_stmt, 1) / sizeof(uint16_t);
				// if weights available, load weights
				ccv_dense_matrix_t* w = 0;
				char wname[256];
				switch (qnum)
				{
					case 0x10:
						sprintf(wname, "layer-%d-4bit-crush.png", sqlite3_column_int(layer_quant_stmt, 0));
						break;
					case 0x100:
						sprintf(wname, "layer-%d-crush.png", sqlite3_column_int(layer_quant_stmt, 0));
						break;
				}
				ccv_read(wname, &w, CCV_IO_ANY_FILE | CCV_IO_GRAY);
				const void* q = sqlite3_column_blob(layer_quant_stmt, 1);
				float f[256];
				ccv_half_precision_to_float((uint16_t*)q, f, qnum);
				int j, k;
				for (j = 0; j < w->rows; j++)
					for (k = 0; k < w->cols; k++)
						layer->w[j * w->cols + k] = f[w->data.u8[j * w->cols + k]];
				ccv_matrix_free(w);
			}
			sqlite3_finalize(layer_quant_stmt);
		}
	}
	sqlite3_close(db);
}