source: sasview/guiframe/local_perspectives/plotting/boxSum.py @ d0d2ab5

import math
import wx
from copy import deepcopy
from BaseInteractor import _BaseInteractor
from sans.guicomm.events import SlicerParamUpdateEvent,EVT_SLICER_PARS,StatusEvent


class BoxSum(_BaseInteractor):
    """
        Boxsum Class: determine 2 rectangular area to compute the sum of pixel of
        a Data. 
        Uses PointerInteractor , VerticalDoubleLine,HorizontalDoubleLine.
        @param zorder:  Artists with lower zorder values are drawn first.
        @param x_min: the minimum value of the x coordinate
        @param x_max: the maximum value of the x coordinate
        @param y_min: the minimum value of the y coordinate
        @param y_max: the maximum value of the y coordinate

    """
    def __init__(self,base,axes,color='black', zorder=3, x_min=0.008,
                  x_max=0.008, y_min=0.0025, y_max=0.0025):
        
        _BaseInteractor.__init__(self, base, axes, color=color)
        ## class initialization
        ## list of Boxsmun markers
        self.markers = []
        self.axes = axes
        ## connect the artist for the motion
        self.connect = self.base.connect
        ## when qmax is reached the selected line is reset the its previous value
        self.qmax = min(self.base.data2D.xmax, self.base.data2D.xmin)
        ## Define the boxsum limits
        self.xmin= -1* 0.5*min(math.fabs(self.base.data2D.xmax),math.fabs( self.base.data2D.xmin))
        self.ymin= -1* 0.5*min(math.fabs(self.base.data2D.xmax),math.fabs( self.base.data2D.xmin))
       
        self.xmax= 0.5*min(math.fabs(self.base.data2D.xmax),math.fabs( self.base.data2D.xmin))
        self.ymax=  0.5*min(math.fabs(self.base.data2D.xmax),math.fabs( self.base.data2D.xmin))
        ## center of the boxSum
        self.center_x= 0.0002
        self.center_y= 0.0003
        ## Number of points on the plot
        self.nbins = 20
        ## Define initial result the summation 
        self.count=0
        self.error=0
        ## Flag to determine if the current figure has moved
        ## set to False == no motion , set to True== motion
        self.has_move= False
        ## Create Boxsum edges 
        self.horizontal_lines= HorizontalDoubleLine(self, self.base.subplot,color='blue',
                                                      zorder=zorder,
                                    y= self.ymax,
                                    x= self.xmax,
                                    center_x= self.center_x,
                                    center_y= self.center_y)
        self.horizontal_lines.qmax = self.qmax
        
        self.vertical_lines= VerticalDoubleLine(self, self.base.subplot,color='black',
                                                      zorder=zorder,
                                    y= self.ymax,
                                    x= self.xmax,
                                    center_x= self.center_x,
                                    center_y= self.center_y)
        self.vertical_lines.qmax = self.qmax
        
        self.center= PointInteractor(self, self.base.subplot,color='grey',
                                                      zorder=zorder,
                                    center_x= self.center_x,
                                    center_y= self.center_y)
        ## Save the name of the slicer panel associate with this slicer 
        self.panel_name=""    
        ## Update and post slicer parameters  
        self.update()
        self._post_data()
        ## Bind to slice parameter events
        self.base.Bind(EVT_SLICER_PARS, self._onEVT_SLICER_PARS)
        
        
    def set_panel_name(self, name):
        """
            Store the name of the panel associated to this slicer
            @param name: the name of this panel
        """
        self.panel_name= name
        
        
    def _onEVT_SLICER_PARS(self, event):
        """
            receive an event containing parameters values to reset the slicer
            @param event: event of type SlicerParameterEvent with params as 
            attribute
        """
        ## Post e message to declare what kind of event has being received
        wx.PostEvent(self.base.parent, StatusEvent(status="Boxsum._onEVT_SLICER_PARS"))
        event.Skip()
        ## reset the slicer with the values contains the event.params dictionary
        if event.type == self.__class__.__name__:
            self.set_params(event.params)
            self.base.update()


    def set_layer(self, n):
        """
             Allow adding plot to the same panel
             @param n: the number of layer
        """
        self.layernum = n
        self.update()
        
        
    def clear(self):
        """
            Clear the slicer and all connected events related to this slicer
        """
        self.clear_markers()
        self.horizontal_lines.clear()
        self.vertical_lines.clear()
        self.center.clear()
        self.base.connect.clearall()
        self.base.Unbind(EVT_SLICER_PARS)
        
        
    def update(self):
        """
            Respond to changes in the model by recalculating the profiles and
            resetting the widgets.
        """
        ## check if the center point has moved and update the figure accordingly 
        if self.center.has_move:
            self.center.update()
            self.horizontal_lines.update( center= self.center)
            self.vertical_lines.update( center= self.center)
        ## check if the horizontal lines have moved and update the figure accordingly    
        if self.horizontal_lines.has_move:
            self.horizontal_lines.update()
            self.vertical_lines.update(y1=self.horizontal_lines.y1,
                                       y2=self.horizontal_lines.y2,
                                       height= self.horizontal_lines.half_height )
        ## check if the vertical lines have moved and update the figure accordingly    
        if self.vertical_lines.has_move:
            self.vertical_lines.update()
            self.horizontal_lines.update(x1=self.vertical_lines.x1,
                                         x2=self.vertical_lines.x2,
                                         width=self.vertical_lines.half_width)
            

    def save(self, ev):
        """
        Remember the roughness for this layer and the next so that we
        can restore on Esc.
        """
        self.base.freeze_axes()
        self.horizontal_lines.save(ev)
        self.vertical_lines.save(ev)
        self.center.save(ev)
        
    def _post_data(self):
        """
            Get the limits of the boxsum and compute the sum of the pixel
            contained in that region and the error on that sum
        """
        ## Data 2D for which the pixel will be summed
        data = self.base.data2D
        ## the region of the summation
        x_min= self.horizontal_lines.x2 
        x_max= self.horizontal_lines.x1 
        y_min= self.vertical_lines.y2
        y_max= self.vertical_lines.y1
        ##computation of the sum and its error
        from DataLoader.manipulations import  Boxavg
        box =  Boxavg (x_min=x_min, x_max=x_max, y_min=y_min, y_max=y_max)
        self.count, self.error = box(self.base.data2D)

                          
    def moveend(self, ev):
        """
            After a dragging motion this function is called to compute
            the error and the sum of pixel of a given data 2D 
        """
        self.base.thaw_axes()
        ## compute error an d sum of data's pixel
        self._post_data()
        ## Create and event ( posted to guiframe)that  set the 
        ##current slicer parameter to a panel of name self.panel_name
        self.type= self.__class__.__name__
        params= self.get_params()
        event = SlicerParamUpdateEvent(type=self.type, params=params,
                                       panel_name= self.panel_name)
        wx.PostEvent(self.base.parent, event)
        
            
    def restore(self):
        """
        Restore the roughness for this layer.
        """
        self.horizontal_lines.restore()
        self.vertical_lines.restore()
        self.center.restore()
        
        
    def move(self, x, y, ev):
        """
        Process move to a new position, making sure that the move is allowed.
        """
        pass
    
    
    def set_cursor(self, x, y):
        pass
        
        
    def get_params(self):
        """
            Store a copy of values of parameters of the slicer into a dictionary.
            @return params: the dictionary created
        """
        params = {}
        params["Width"] = math.fabs(self.vertical_lines.half_width)*2
        params["Height"] = math.fabs(self.horizontal_lines.half_height)*2 
        params["center_x"] = self.center.x
        params["center_y"] =self.center.y
        params["count"] = self.count
        params["errors"]= self.error
        return params
    
    
    def get_result(self):
        """
            return the result of box summation
        """
        result={}
        result["count"] = self.count
        result["error"] = self.error
        return result
        
        
    def set_params(self, params):
        """
            Receive a dictionary and reset the slicer with values contained 
            in the values of the dictionary.
            @param params: a dictionary containing name of slicer parameters and 
            values the user assigned to the slicer.
        """
        x_max = math.fabs(params["Width"] )/2
        y_max = math.fabs(params["Height"] )/2
        
        self.center_x=params["center_x"] 
        self.center_y=params["center_y"]
        #update the slicer given values of params
        self.center.update(center_x=self.center_x,center_y=self.center_y)
        self.horizontal_lines.update(center= self.center,
                                     width=x_max,
                                     height=y_max)
        self.vertical_lines.update(center= self.center,
                                    width=x_max,
                                    height=y_max)
        #compute the new error and sum given values of params
        self._post_data()
        
       
        
    def freeze_axes(self):
        self.base.freeze_axes()
        
        
    def thaw_axes(self):
        self.base.thaw_axes()


    def draw(self):
        self.base.draw()
        
        
        
class PointInteractor(_BaseInteractor):
    """
         Draw a point that can be dragged with the marker.
         this class controls the motion the center of the BoxSum 
    """
    def __init__(self,base,axes,color='black', zorder=5,
                 center_x= 0.0,
                 center_y= 0.0):
        
        _BaseInteractor.__init__(self, base, axes, color=color)
        ## Initialization the class 
        self.markers = []
        self.axes = axes
        # center coordinates
        self.x = center_x
        self.y = center_y
        ## saved value of the center coordinates
        self.save_x = center_x
        self.save_y = center_y
        ## Create a marker 
        try:
            self.center_marker = self.axes.plot([self.x],[self.y], linestyle='',
                                          marker='s', markersize=10,
                                          color=self.color, alpha=0.6,
                                          pickradius=5, label="pick", 
                                          zorder=zorder, # Prefer this to other lines
                                          visible=True)[0]
        except:
            self.center_marker = self.axes.plot([self.x],[self.y], linestyle='',
                                          marker='s', markersize=10,
                                          color=self.color, alpha=0.6,
                                          label="pick", 
                                          visible=True)[0]
            message  = "\nTHIS PROTOTYPE NEEDS THE LATEST VERSION OF MATPLOTLIB\n"
            message += "Get the SVN version that is at least as recent as June 1, 2007"
            owner=self.base.base.parent
            wx.PostEvent(owner, StatusEvent(status="AnnulusSlicer: %s"%message))
            
        ## Draw a point
        self.center = self.axes.plot([self.x],[self.y],
                                      linestyle='-', marker='',
                                      color=self.color,
                                      visible=True)[0]
        ## Flag to determine the motion this point 
        self.has_move=False   
        ## connecting the marker to allow them to move 
        self.connect_markers([self.center_marker])
        ## Update the figure
        self.update()
    
    
    def set_layer(self, n):
        """
            Allow adding plot to the same panel
            @param n: the number of layer
        """
        self.layernum = n
        self.update()
        
        
    def clear(self):
        """
            Clear this figure and its markers
        """
        self.clear_markers()
        try:
            self.center.remove()
            self.center_marker.remove()
        except:
            # Old version of matplotlib
            for item in range(len(self.axes.lines)):
                del self.axes.lines[0]
  
   
    def update(self, center_x=None,center_y=None):
        """
            Draw the new roughness on the graph.
        """
        if center_x !=None: self.x= center_x
        if center_y !=None: self.y= center_y
   
        self.center_marker.set(xdata=[self.x], ydata=[self.y])
        self.center.set(xdata=[self.x], ydata=[self.y])
        
        
    def save(self, ev):
        """
        Remember the roughness for this layer and the next so that we
        can restore on Esc.
        """
        self.save_x= self.x
        self.save_y= self.y
        self.base.freeze_axes()


    def moveend(self, ev):
        
        self.has_move=False
        self.base.moveend(ev)
            
    def restore(self):
        """
        Restore the roughness for this layer.
        """
        self.y= self.save_y
        self.x= self.save_x
        
        
    def move(self, x, y, ev):
        """
        Process move to a new position, making sure that the move is allowed.
        """
        self.x= x
        self.y= y
       
        self.has_move=True
        self.base.base.update()
        
        
    def set_cursor(self, x, y):
        self.move(x, y, None)
        self.update()
        
        
    def get_params(self):
        params = {}
        params["x"] = self.x
        params["y"] = self.y
        return params
    
    
    def set_params(self, params):
        center_x = params["x"] 
        center_y = params["y"] 
        self.update(center_x=center_x,center_y=center_y)
       
        
class VerticalDoubleLine(_BaseInteractor):
    """
         Draw 2 vertical lines moving in opposite direction and centered on 
         a point (PointInteractor)
    """
    def __init__(self,base,axes,color='black', zorder=5, x=0.5,y=0.5,
                 center_x= 0.0,
                 center_y= 0.0):
        
        _BaseInteractor.__init__(self, base, axes, color=color)
        ## Initialization the class 
        self.markers = []
        self.axes = axes
        ## Center coordinates
        self.center_x = center_x
        self.center_y = center_y
        ## defined end points vertical lignes and their saved values
        self.y1     = y + self.center_y
        self.save_y1= self.y1
        
        delta= self.y1- self.center_y
        self.y2= self.center_y - delta
        self.save_y2= self.y2
        
        self.x1      = x + self.center_x
        self.save_x1 = self.x1
         
        delta= self.x1- self.center_x
        self.x2= self.center_x - delta
        self.save_x2 = self.x2
        ## save the color of the line
        self.color = color
        ## the height of the rectangle
        self.half_height= math.fabs(y)
        self.save_half_height= math.fabs(y)
        ## the with of the rectangle
        self.half_width= math.fabs(self.x1- self.x2)/2
        self.save_half_width=math.fabs(self.x1- self.x2)/2
        ## Create marker 
        try:
            self.right_marker = self.axes.plot([self.x1],[0], linestyle='',
                                          marker='s', markersize=10,
                                          color=self.color, alpha=0.6,
                                          pickradius=5, label="pick", 
                                          zorder=zorder, # Prefer this to other lines
                                          visible=True)[0]
        except:
            self.right_marker = self.axes.plot([self.x1],[0], linestyle='',
                                          marker='s', markersize=10,
                                          color=self.color, alpha=0.6,
                                          label="pick", 
                                          visible=True)[0]
            message  = "\nTHIS PROTOTYPE NEEDS THE LATEST VERSION OF MATPLOTLIB\n"
            message += "Get the SVN version that is at least as recent as June 1, 2007"
            owner=self.base.base.parent
            wx.PostEvent(owner, StatusEvent(status="AnnulusSlicer: %s"%message))
            
        ## define the left and right lines of the rectangle
        self.right_line = self.axes.plot([self.x1,self.x1],[self.y1,self.y2],
                                      linestyle='-', marker='',
                                      color=self.color,
                                      visible=True)[0]
        self.left_line = self.axes.plot([self.x2,self.x2],[self.y1,self.y2],
                                      linestyle='-', marker='',
                                      color=self.color,
                                      visible=True)[0]
        ## Flag to determine if the lines have moved
        self.has_move=False  
        ## connection the marker and draw the pictures  
        self.connect_markers([self.right_marker])
        self.update()


    def set_layer(self, n):
        """
            Allow adding plot to the same panel
            @param n: the number of layer
        """
        self.layernum = n
        self.update()
        
        
    def clear(self):
        """
            Clear this slicer  and its markers
        """
        self.clear_markers()
        try:
            self.right_marker.remove()
            self.right_line.remove()
            self.left_line.remove()
        except:
            # Old version of matplotlib
            for item in range(len(self.axes.lines)):
                del self.axes.lines[0]
   
   
    def update(self,x1=None,x2=None, y1=None,y2=None,width=None, height=None, center=None):
        """
            Draw the new roughness on the graph.
            @param x1: new maximum value of x coordinates
            @param x2: new minimum value of x coordinates
            @param y1: new maximum value of y coordinates
            @param y2: new minimum value of y coordinates
            @param width: is the width of the new rectangle
            @param height: is the height of the new rectangle
            @param center: provided x, y  coordinates of the center point
        """
        ## save the new height, witdh of the rectangle if given as a param
        if width!=None:
            self.half_width= width
        if height!=None:
            self.half_height= height
        ## If new  center coordinates are given draw the rectangle 
        ##given these value 
        if center!=None:
            self.center_x= center.x
            self.center_y= center.y
            
            self.x1 = self.half_width + self.center_x
            self.x2= -self.half_width + self.center_x
            
            self.y1 = self.half_height + self.center_y
            self.y2= -self.half_height + self.center_y
         
            self.right_marker.set(xdata=[self.x1],ydata=[self.center_y])
            self.right_line.set(xdata=[self.x1,self.x1], ydata=[self.y1,self.y2])
            self.left_line.set(xdata=[self.x2,self.x2], ydata=[self.y1,self.y2])
            return 
        ## if x1, y1, y2, y3 are given draw the rectangle with this value
        if x1 !=None: 
            self.x1= x1
        if x2 !=None: 
            self.x2= x2
        if y1 !=None: 
            self.y1= y1
        if y2 !=None: 
            self.y2= y2
        ## Draw 2 vertical lines and a marker 
        self.right_marker.set(xdata=[self.x1],ydata=[self.center_y])
        self.right_line.set(xdata=[self.x1,self.x1], ydata=[self.y1,self.y2])
        self.left_line.set(xdata=[self.x2,self.x2], ydata=[self.y1,self.y2])
        
        
    def save(self, ev):
        """
        Remember the roughness for this layer and the next so that we
        can restore on Esc.
        """
        self.save_x2= self.x2
        self.save_y2= self.y2
        
        self.save_x1= self.x1
        self.save_y1= self.y1
        
        self.save_half_height= self.half_height
        self.save_half_width = self.half_width
        
        self.base.freeze_axes()


    def moveend(self, ev):
        """
            After a dragging motion reset the flag self.has_move to False
        """
        self.has_move=False
        self.base.moveend(ev)
            
            
    def restore(self):
        """
        Restore the roughness for this layer.
        """
        self.y2= self.save_y2
        self.x2= self.save_x2
        
        self.y1= self.save_y1
        self.x1= self.save_x1
        
        self.half_height= self.save_half_height
        self.half_width= self.save_half_width
       
       
    def move(self, x, y, ev):
        """
        Process move to a new position, making sure that the move is allowed.
        """
        self.x1= x
        delta= self.x1- self.center_x
        self.x2= self.center_x - delta
        
        self.half_width= math.fabs(self.x1-self.x2)/2
        
        self.has_move=True
        self.base.base.update()
        
        
    def set_cursor(self, x, y):
        """
            Update the figure given x and y 
        """
        self.move(x, y, None)
        self.update()
        
        
    def get_params(self):
        """
            Store a copy of values of parameters of the slicer into a dictionary.
            @return params: the dictionary created
        """
        params = {}
        params["x"] = self.x1
        params["y"] = self.y1
        
        return params
    
    def set_params(self, params):
        """
            Receive a dictionary and reset the slicer with values contained 
            in the values of the dictionary.
            @param params: a dictionary containing name of slicer parameters and 
            values the user assigned to the slicer.
        """
        x = params["x"] 
        y = params["y"] 
        self.update(x=x, y=y, center_x=None,center_y=None)


class HorizontalDoubleLine(_BaseInteractor):
    """
         Select an annulus through a 2D plot
    """
    def __init__(self,base,axes,color='black', zorder=5, x=0.5,y=0.5,
                 center_x= 0.0,
                 center_y= 0.0):
        
        _BaseInteractor.__init__(self, base, axes, color=color)
        ## Initialization the class 
        self.markers = []
        self.axes = axes
        ## Center coordinates
        self.center_x = center_x
        self.center_y = center_y
        
        self.y1     = y + self.center_y
        self.save_y1= self.y1
        
        delta= self.y1- self.center_y
        self.y2=  self.center_y - delta
        self.save_y2= self.y2
        
        self.x1      = x + self.center_x
        self.save_x1 = self.x1
        
        delta= self.x1- self.center_x
        self.x2=  self.center_x - delta
        self.save_x2 = self.x2
        
        self.color=color
        
        self.half_height= math.fabs(y)
        self.save_half_height= math.fabs(y)
        
        self.half_width= math.fabs(x)
        self.save_half_width=math.fabs(x)
    
        try:
            self.top_marker = self.axes.plot([0],[self.y1], linestyle='',
                                          marker='s', markersize=10,
                                          color=self.color, alpha=0.6,
                                          pickradius=5, label="pick", 
                                          zorder=zorder, # Prefer this to other lines
                                          visible=True)[0]
        except:
            self.top_marker = self.axes.plot([0],[self.y1], linestyle='',
                                          marker='s', markersize=10,
                                          color=self.color, alpha=0.6,
                                          label="pick", 
                                          visible=True)[0]
            message  = "\nTHIS PROTOTYPE NEEDS THE LATEST VERSION OF MATPLOTLIB\n"
            message += "Get the SVN version that is at least as recent as June 1, 2007"
            owner=self.base.base.parent
            wx.PostEvent(owner, StatusEvent(status="AnnulusSlicer: %s"%message))
            
        # Define 2 horizotnal lines
        self.top_line = self.axes.plot([self.x1,-self.x1],[self.y1,self.y1],
                                      linestyle='-', marker='',
                                      color=self.color,
                                      visible=True)[0]
        self.bottom_line = self.axes.plot([self.x1,-self.x1],[self.y2,self.y2],
                                      linestyle='-', marker='',
                                      color=self.color,
                                      visible=True)[0]
        ## Flag to determine if the lines have moved
        self.has_move=False    
        ## connection the marker and draw the pictures 
        self.connect_markers([self.top_marker])
        self.update()


    def set_layer(self, n):
        """
            Allow adding plot to the same panel
            @param n: the number of layer
        """
        self.layernum = n
        self.update()
        
        
    def clear(self):
        """
            Clear this figure and its markers
        """
        self.clear_markers()
        try:
            self.top_marker.remove()
            self.bottom_line.remove()
            self.top_line.remove()
        except:
            # Old version of matplotlib
            for item in range(len(self.axes.lines)):
                del self.axes.lines[0]
    
   
    def update(self,x1=None,x2=None, y1=None,y2=None,width=None,height=None, center=None):
        """
            Draw the new roughness on the graph.
            @param x1: new maximum value of x coordinates
            @param x2: new minimum value of x coordinates
            @param y1: new maximum value of y coordinates
            @param y2: new minimum value of y coordinates
            @param width: is the width of the new rectangle
            @param height: is the height of the new rectangle
            @param center: provided x, y  coordinates of the center point
        """
        ## save the new height, witdh of the rectangle if given as a param
        if width != None:
            self.half_width = width
        if height!= None:
            self.half_height= height
        ## If new  center coordinates are given draw the rectangle 
        ##given these value 
        if center!=None:
            self.center_x= center.x
            self.center_y= center.y
            
            self.x1 = self.half_width + self.center_x
            self.x2= -self.half_width + self.center_x
            
            self.y1 = self.half_height + self.center_y
            self.y2= -self.half_height + self.center_y
            
            self.top_marker.set(xdata=[self.center_x],ydata=[self.y1])
            self.top_line.set(xdata=[self.x1,self.x2], ydata=[self.y1,self.y1])
            self.bottom_line.set(xdata=[self.x1,self.x2], ydata=[self.y2,self.y2])
            return 
        ## if x1, y1, y2, y3 are given draw the rectangle with this value
        if x1 !=None: 
            self.x1= x1
        if x2 !=None: 
            self.x2= x2
        if y1 !=None: 
            self.y1= y1
        if y2 !=None: 
            self.y2= y2
        ## Draw 2 vertical lines and a marker 
        self.top_marker.set(xdata=[self.center_x],ydata=[self.y1])
        self.top_line.set(xdata=[self.x1,self.x2], ydata=[self.y1,self.y1])
        self.bottom_line.set(xdata=[self.x1,self.x2], ydata=[self.y2,self.y2])
       
        
    def save(self, ev):
        """
        Remember the roughness for this layer and the next so that we
        can restore on Esc.
        """
        self.save_x2= self.x2
        self.save_y2= self.y2
        
        self.save_x1= self.x1
        self.save_y1= self.y1
        
        self.save_half_height= self.half_height
        self.save_half_width =  self.half_width
        self.base.freeze_axes()


    def moveend(self, ev):
        """
            After a dragging motion reset the flag self.has_move to False
        """
        self.has_move=False
        self.base.moveend(ev)
           
            
    def restore(self):
        """
        Restore the roughness for this layer.
        """
        self.y2= self.save_y2
        self.x2= self.save_x2
        
        self.y1= self.save_y1
        self.x1= self.save_x1
        self.half_height= self.save_half_height
        self.half_width= self.save_half_width
        
        
    def move(self, x, y, ev):
        """
        Process move to a new position, making sure that the move is allowed.
        """
        self.y1= y
        delta= self.y1- self.center_y
        self.y2=  self.center_y - delta
        self.half_height=  math.fabs(self.y1)-self.center_y
        self.has_move=True
        self.base.base.update()
        
        
    def set_cursor(self, x, y):
        """
            Update the figure given x and y 
        """
        self.move(x, y, None)
        self.update()
        
        
    def get_params(self):
        """
            Store a copy of values of parameters of the slicer into a dictionary.
            @return params: the dictionary created
        """
        params = {}
        params["x"] = self.x
        params["y"] = self.y
        return params
    
    
    def set_params(self, params):
        """
            Receive a dictionary and reset the slicer with values contained 
            in the values of the dictionary.
            @param params: a dictionary containing name of slicer parameters and 
            values the user assigned to the slicer.
        """
        x = params["x"] 
        y = params["y"] 
        self.update(x=x, y=y, center_x=None,center_y=None)