get pose(x,y) of any unoccupied cell from 2D occupancy grid [closed]

edit

I wish to be able to calculate the pose(x,y) of any unoccupied grid in the occupancy grid from the occupancyGrid message type here . I wish to use the map int8[ ] data which contains the probability of occupancy of each grid. I need to do so for an algorithm I'm working on. Here are several snippets on how I plan to accomplish this, please be aware that alot of the code before and inbetween have been skipped to cut out information unimportant to the focus of this question:

   ...............................
    self.occ_gridmap = rospy.wait_for_message("/map", OccupancyGrid)
    self.fullmap = np.array(self.occ_gridmap.data)
    self.free_grid=np.where(self.fullmap==0)
    self.width = self.occ_gridmap.info.width
    self.height = self.occ_gridmap.info.height
    self.origin_x = self.occ_gridmap.info.origin.position.x
    self.origin_y = self.occ_gridmap.info.origin.position.y

    ...............................
    def cell_grid(self, index):
        e_row = index % self.height
        e_column = ((index - e_row) / self.width)
        return [e_row, e_column]


    ....................................
    def pose_calculator(self,grid_location):
        x=(grid_location[0]*self.resolution)+self.origin_x
        y=(grid_location[1] * self.resolution) + self.origin_y
        #print("x,y",[x,y])
        return [x,y]


    ................................
    def mapmaker(self):
        q=[]

        for i in range(len(self.free_grid[0])):
            #self.cells.append(self.grid_calculator(self.free_grid[0][i]))
            self.cells.append(self.cell_grid(self.free_grid[0][i]))
        for i in range(len(self.cells)):
            self.cells_array.append(self.pose_calculator(self.cells[i]))

As seen above self.free_grid is supposed to hold all cells with value 0(unoccupied cells) and I try to use map,resolution,origin,width and height. The problem is this doesn't seem to work. for instance, when I recalculate occupancy grid data from some of the poses (x,y) I calculated from self.free_grid, I end up with cells that do not have a value of 0. Is there a more accurate way to do this?