"""module for producing astronomical plots

(c) 2007-2013 Matt Hilton 

U{http://astlib.sourceforge.net}

This module provides the matplotlib powered ImagePlot class, which is designed to be flexible. 
ImagePlots can have RA, Dec. coordinate axes, contour overlays, and have objects marked in them, 
using WCS coordinates. RGB plots are supported too.

@var DEC_TICK_STEPS: Defines the possible coordinate label steps on the delination axis in
sexagesimal mode. Dictionary format: {'deg', 'unit'}
@type DEC_TICK_STEPS: dictionary list

@var RA_TICK_STEPS: Defines the possible coordinate label steps on the right ascension axis in
sexagesimal mode. Dictionary format: {'deg', 'unit'}
@type RA_TICK_STEPS: dictionary list

@var DECIMAL_TICK_STEPS: Defines the possible coordinate label steps on both coordinate axes in
decimal degrees mode.
@type DECIMAL_TICK_STEPS: list

@var DEG: Variable to stand in for the degrees symbol.
@type DEG: string

@var PRIME: Variable to stand in for the prime symbol.
@type PRIME: string

@var DOUBLE_PRIME: Variable to stand in for the double prime symbol.
@type DOUBLE_PRIME: string

"""

import math
from . import astImages
from . import astWCS
from . import astCoords
import numpy
import pyfits
from scipy import interpolate
import pylab
import matplotlib.patches as patches
import sys

# Handle unicode python 2 and 3
if sys.version < '3':
    import codecs
    def u(x):
        return codecs.unicode_escape_decode(x)[0]
else:
    def u(x):
        return x
    
DEC_TICK_STEPS=[{'deg': 1.0/60.0/60.0,  'unit': "s"}, 
                {'deg': 2.0/60.0/60.0,  'unit': "s"},
                {'deg': 5.0/60.0/60.0,  'unit': "s"}, 
                {'deg': 10.0/60.0/60.0, 'unit': "s"},
                {'deg': 30.0/60.0/60.0, 'unit': "s"},
                {'deg': 1.0/60.0,       'unit': "m"},
                {'deg': 2.0/60.0,       'unit': "m"},
                {'deg': 5.0/60.0,       'unit': "m"},
                {'deg': 15.0/60.0,      'unit': "m"},
                {'deg': 30.0/60.0,      'unit': "m"}, 
                {'deg': 1.0,            'unit': "d"},
                {'deg': 2.0,            'unit': "d"},
                {'deg': 4.0,            'unit': "d"},
                {'deg': 5.0,            'unit': "d"},
                {'deg': 10.0,           'unit': "d"},
                {'deg': 20.0,           'unit': "d"},
                {'deg': 30.0,           'unit': "d"}]

RA_TICK_STEPS=[ {'deg': (0.5/60.0/60.0/24.0)*360.0,  'unit': "s"},
                {'deg': (1.0/60.0/60.0/24.0)*360.0,  'unit': "s"},
                {'deg': (2.0/60.0/60.0/24.0)*360.0,  'unit': "s"}, 
                {'deg': (4.0/60.0/60.0/24.0)*360.0,  'unit': "s"}, 
                {'deg': (5.0/60.0/60.0/24.0)*360.0,  'unit': "s"}, 
                {'deg': (10.0/60.0/60.0/24.0)*360.0, 'unit': "s"},
                {'deg': (20.0/60.0/60.0/24.0)*360.0, 'unit': "s"},
                {'deg': (30.0/60.0/60.0/24.0)*360.0, 'unit': "s"},
                {'deg': (1.0/60.0/24.0)*360.0,       'unit': "m"},
                {'deg': (2.0/60.0/24.0)*360.0,       'unit': "m"},
                {'deg': (5.0/60.0/24.0)*360.0,       'unit': "m"},
                {'deg': (10.0/60.0/24.0)*360.0,      'unit': "m"},
                {'deg': (20.0/60.0/24.0)*360.0,      'unit': "m"},
                {'deg': (30.0/60.0/24.0)*360.0,      'unit': "m"}, 
                {'deg': (1.0/24.0)*360.0,            'unit': "h"},
                {'deg': (3.0/24.0)*360.0,            'unit': "h"},
                {'deg': (6.0/24.0)*360.0,            'unit': "h"},
                {'deg': (12.0/24.0)*360.0,           'unit': "h"}]

DECIMAL_TICK_STEPS=[0.001, 0.0025, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.0, 2.5, 5.0, 10.0, 30.0, 90.0]

DEG = u("\N{DEGREE SIGN}")
PRIME = "$^\prime$"
DOUBLE_PRIME = "$^{\prime\prime}$"

#---------------------------------------------------------------------------------------------------
class ImagePlot:
    """This class describes a matplotlib image plot containing an astronomical image with an
    associated WCS.
    
    Objects within the image boundaries can be marked by passing their WCS coordinates to 
    L{ImagePlot.addPlotObjects}.
    
    Other images can be overlaid using L{ImagePlot.addContourOverlay}.
    
    For images rotated with North at the top, East at the left (as can be done using
    L{astImages.clipRotatedImageSectionWCS} or L{astImages.resampleToTanProjection}, WCS coordinate
    axes can be plotted, with tick marks set appropriately for the image size. Otherwise, a compass 
    can be plotted showing the directions of North and East in the image.

    RGB images are also supported.
    
    The plot can of course be tweaked further after creation using matplotlib/pylab commands.
    
    """
    def __init__(self, imageData, imageWCS, axes = [0.1,0.1,0.8,0.8], \
        cutLevels = ["smart", 99.5], colorMapName = "gray", title = None, axesLabels = "sexagesimal", \
        axesFontFamily="serif", axesFontSize=12.0, RATickSteps="auto", decTickSteps="auto",
        colorBar = False, interpolation = "bilinear"):
        """Makes an ImagePlot from the given image array and astWCS. For coordinate axes to work, the
        image and WCS should have been rotated such that East is at the left, North is at the top
        (see e.g. L{astImages.clipRotatedImageSectionWCS}, or L{astImages.resampleToTanProjection}).
        
        If imageData is given as a list in the format [r, g, b], a color RGB plot will be made. However,
        in this case the cutLevels must be specified manually for each component as a list -
        i.e. cutLevels = [[r min, r max], [g min, g max], [b min, b max]]. In this case of course, the
        colorMap will be ignored. All r, g, b image arrays must have the same dimensions.
        
        Set axesLabels = None to make a plot without coordinate axes plotted.
        
        The axes can be marked in either sexagesimal or decimal celestial coordinates. If RATickSteps
        or decTickSteps are set to "auto", the appropriate axis scales will be determined automatically 
        from the size of the image array and associated WCS. The tick step sizes can be overidden. 
        If the coordinate axes are in sexagesimal format a dictionary in the format {'deg', 'unit'} is 
        needed (see L{RA_TICK_STEPS} and L{DEC_TICK_STEPS} for examples). If the coordinate axes are in
        decimal format, the tick step size is specified simply in RA, dec decimal degrees.
        
        @type imageData: numpy array or list
        @param imageData: image data array or list of numpy arrays [r, g, b]
        @type imageWCS: astWCS.WCS
        @param imageWCS: astWCS.WCS object
        @type axes: list
        @param axes: specifies where in the current figure to draw the finder chart (see pylab.axes)
        @type cutLevels: list
        @param cutLevels: sets the image scaling - available options:
            - pixel values: cutLevels=[low value, high value].
            - histogram equalisation: cutLevels=["histEq", number of bins ( e.g. 1024)]
            - relative: cutLevels=["relative", cut per cent level (e.g. 99.5)]
            - smart: cutLevels=["smart", cut per cent level (e.g. 99.5)]
        ["smart", 99.5] seems to provide good scaling over a range of different images.
        Note that for RGB images, cut levels must be specified manually i.e. as a list:
        [[r min, rmax], [g min, g max], [b min, b max]]
        @type colorMapName: string
        @param colorMapName: name of a standard matplotlib colormap, e.g. "hot", "cool", "gray"
        etc. (do "help(pylab.colormaps)" in the Python interpreter to see available options)
        @type title: string
        @param title: optional title for the plot
        @type axesLabels: string
        @param axesLabels: either "sexagesimal" (for H:M:S, D:M:S), "decimal" (for decimal degrees)
        or None (for no coordinate axes labels)
        @type axesFontFamily: string
        @param axesFontFamily: matplotlib fontfamily, e.g. 'serif', 'sans-serif' etc.
        @type axesFontSize: float
        @param axesFontSize: font size of axes labels and titles (in points)
        @type colorBar: bool
        @param colorBar: if True, plot a vertical color bar at the side of the image indicating the intensity
        scale.
        @type interpolation: string
        @param interpolation: interpolation to apply to the image plot (see the documentation for
                              the matplotlib.pylab.imshow command)
        
        """
                
        self.RADeg, self.decDeg=imageWCS.getCentreWCSCoords()
        self.wcs=imageWCS
        
        # Handle case where imageData is [r, g, b]
        if type(imageData) == list:
            if len(imageData) == 3:
                if len(cutLevels) == 3:
                    r=astImages.normalise(imageData[0], cutLevels[0])
                    g=astImages.normalise(imageData[1], cutLevels[1])
                    b=astImages.normalise(imageData[2], cutLevels[2])
                    rgb=numpy.array([r.transpose(), g.transpose(), b.transpose()])
                    rgb=rgb.transpose()
                    self.data=rgb
                    self.rgbImage=True
                else:
                    raise Exception("tried to create a RGB array, but cutLevels is not a list of 3 lists")

            else:
                raise Exception("tried to create a RGB array but imageData is not a list of 3 arrays")
        else:
            self.data=imageData
            self.rgbImage=False
        
        self.axes=pylab.axes(axes)
        self.cutLevels=cutLevels
        self.colorMapName=colorMapName
        self.title=title
        self.axesLabels=axesLabels
        self.colorBar=colorBar
        self.axesFontSize=axesFontSize
        self.axesFontFamily=axesFontFamily
        
        self.flipXAxis=False
        self.flipYAxis=False
                
        self.interpolation=interpolation
        
        if self.axesLabels != None:
            
            # Allow user to override the automatic coord tick spacing
            if self.axesLabels == "sexagesimal":
                if RATickSteps != "auto":
                    if type(RATickSteps) != dict or "deg" not in list(RATickSteps.keys()) \
                            or "unit" not in list(RATickSteps.keys()):
                        raise Exception("RATickSteps needs to be in format {'deg', 'unit'} for sexagesimal axes labels")
                if decTickSteps != "auto":
                    if type(decTickSteps) != dict or "deg" not in list(decTickSteps.keys()) \
                            or "unit" not in list(decTickSteps.keys()):
                        raise Exception("decTickSteps needs to be in format {'deg', 'unit'} for sexagesimal axes labels")
            elif self.axesLabels == "decimal":
                if RATickSteps != "auto":
                    if type(RATickSteps) != float:
                        raise Exception("RATickSteps needs to be a float (if not 'auto') for decimal axes labels")
                if decTickSteps != "auto":
                    if type(decTickSteps) != float:
                        raise Exception("decTickSteps needs to be a float (if not 'auto') for decimal axes labels")
            self.RATickSteps=RATickSteps
            self.decTickSteps=decTickSteps
        
            self.calcWCSAxisLabels(axesLabels = self.axesLabels)
        
        # this list stores objects to overplot, add to it using addPlotObjects()
        self.plotObjects=[] 
        
        # this list stores image data to overlay as contours, add to it using addContourOverlay()
        self.contourOverlays=[]
        
        self.draw()


    def draw(self):
        """Redraws the ImagePlot.
        
        """
        
        pylab.axes(self.axes)
        pylab.cla()
        
        if self.title != None:
            pylab.title(self.title)
        try:
            colorMap=pylab.cm.get_cmap(self.colorMapName)
        except AssertionError:
            raise Exception(self.colorMapName+"is not a defined matplotlib colormap.")
        
        if self.rgbImage == False:
            self.cutImage=astImages.intensityCutImage(self.data, self.cutLevels)
            if self.cutLevels[0]=="histEq":
                pylab.imshow(self.cutImage['image'],  interpolation=self.interpolation, origin='lower', cmap=colorMap)
            else:
                pylab.imshow(self.cutImage['image'],  interpolation=self.interpolation,  norm=self.cutImage['norm'], \
                            origin='lower', cmap=colorMap)
        else:
            pylab.imshow(self.data, interpolation="bilinear", origin='lower')
        
        if self.colorBar == True:
            pylab.colorbar(shrink=0.8)
        
        for c in self.contourOverlays:
            pylab.contour(c['contourData']['scaledImage'], c['contourData']['contourLevels'], 
                            colors=c['color'], linewidths=c['width'])
        
        for p in self.plotObjects:
            for x, y, l in zip(p['x'], p['y'], p['objLabels']):
                if p['symbol'] == "circle":
                    c=patches.Circle((x, y), radius=p['sizePix']/2.0, fill=False, edgecolor=p['color'], 
                                        linewidth=p['width'])
                    self.axes.add_patch(c)
                elif p['symbol'] == "box":
                    c=patches.Rectangle((x-p['sizePix']/2, y-p['sizePix']/2), p['sizePix'], p['sizePix'], 
                        fill=False, edgecolor=p['color'], linewidth=p['width'])
                    self.axes.add_patch(c)
                elif p['symbol'] == "cross":
                    pylab.plot([x-p['sizePix']/2, x+p['sizePix']/2], [y, y], linestyle='-', 
                        linewidth=p['width'], color= p['color'])
                    pylab.plot([x, x], [y-p['sizePix']/2, y+p['sizePix']/2], linestyle='-', 
                        linewidth=p['width'], color= p['color'])
                elif p['symbol'] == "diamond":
                    c=patches.RegularPolygon([x, y], 4, radius=p['sizePix']/2, orientation=0, 
                                            edgecolor=p['color'], fill=False, linewidth=p['width'])
                    self.axes.add_patch(c)
                if l != None:
                    pylab.text(x, y+p['sizePix']/1.5, l, horizontalalignment='center', \
                                fontsize=p['objLabelSize'], color=p['color'])
            
            if p['symbol'] == "compass":
                x=p['x'][0]
                y=p['y'][0]
                ra=p['RA'][0]
                dec=p['dec'][0]
                
                westPoint,eastPoint,southPoint,northPoint=astCoords.calcRADecSearchBox(ra, dec, p['sizeArcSec']/3600.0/2.0)
                northPix=self.wcs.wcs2pix(ra, northPoint)
                eastPix=self.wcs.wcs2pix(eastPoint, dec)
                                
                edx=eastPix[0]-x
                edy=eastPix[1]-y
                ndx=northPix[0]-x
                ndy=northPix[1]-y
                nArrow=patches.Arrow(x, y, ndx, ndy, edgecolor=p['color'], facecolor=p['color'], width=p['width'])
                eArrow=patches.Arrow(x, y, edx, edy, edgecolor=p['color'], facecolor=p['color'], width=p['width'])                
                self.axes.add_patch(nArrow)
                self.axes.add_patch(eArrow)
                pylab.text(x+ndx+ndx*0.2, y+ndy+ndy*0.2, "N", horizontalalignment='center', 
                                verticalalignment='center', fontsize=p['objLabelSize'], color=p['color'])
                pylab.text(x+edx+edx*0.2, y+edy+edy*0.2, "E", horizontalalignment='center', 
                                verticalalignment='center', fontsize=p['objLabelSize'], color=p['color'])

            if p['symbol'] == "scaleBar":
                x=p['x'][0]
                y=p['y'][0]
                ra=p['RA'][0]
                dec=p['dec'][0]
                
                westPoint,eastPoint,southPoint,northPoint=astCoords.calcRADecSearchBox(ra, dec, p['sizeArcSec']/3600.0/2.0)
                northPix=self.wcs.wcs2pix(ra, northPoint)
                eastPix=self.wcs.wcs2pix(eastPoint, dec)
                edx=eastPix[0]-x
                edy=eastPix[1]-y
                ndx=northPix[0]-x
                ndy=northPix[1]-y
                                
                eArrow=patches.Arrow(x, y, edx, edy, edgecolor=p['color'], facecolor=p['color'], width=p['width'])  
                wArrow=patches.Arrow(x, y, -edx, edy, edgecolor=p['color'], facecolor=p['color'], width=p['width'])                

                self.axes.add_patch(eArrow)
                self.axes.add_patch(wArrow)
                
                # Work out label
                scaleLabel=None
                if p['sizeArcSec'] < 60.0:
                    scaleLabel="%.0f %s" % (p['sizeArcSec'], DOUBLE_PRIME)
                elif p['sizeArcSec'] >= 60.0 and p['sizeArcSec'] <  3600.0:
                    scaleLabel="%.0f %s" % (p['sizeArcSec']/60.0, PRIME)
                else:
                    scaleLabel="%.0f %s" % (p['sizeArcSec']/3600.0, DEG)
                    
                pylab.text(x, y+0.025*self.data.shape[1], scaleLabel, horizontalalignment='center', 
                                verticalalignment='center', fontsize=p['objLabelSize'], color=p['color'])
                                
        if self.axesLabels != None:
            pylab.xticks(self.ticsRA[0], self.ticsRA[1], weight='normal', family=self.axesFontFamily, \
                                    fontsize=self.axesFontSize)
            pylab.yticks(self.ticsDec[0], self.ticsDec[1], weight='normal', family=self.axesFontFamily, \
                                    fontsize=self.axesFontSize)
            pylab.xlabel(self.RAAxisLabel, family=self.axesFontFamily, fontsize=self.axesFontSize)
            pylab.ylabel(self.decAxisLabel, family=self.axesFontFamily, fontsize=self.axesFontSize)
        else:
            pylab.xticks([], [])
            pylab.yticks([], [])
            pylab.xlabel("")
            pylab.ylabel("")
        
        if self.flipXAxis == False:
            pylab.xlim(0, self.data.shape[1]-1)
        else:
            pylab.xlim(self.data.shape[1]-1, 0)
        if self.flipYAxis == False:
            pylab.ylim(0, self.data.shape[0]-1)
        else:
            pylab.ylim(self.data.shape[0]-1, 0)


    def addContourOverlay(self, contourImageData, contourWCS, tag, levels = ["linear", "min", "max", 5],
                             width = 1, color = "white", smooth = 0, highAccuracy = False):
        """Adds image data to the ImagePlot as a contour overlay. The contours can be removed using 
        L{removeContourOverlay}. If a contour overlay already exists with this tag, it will be replaced.
        
        @type contourImageData: numpy array
        @param contourImageData: image data array from which contours are to be generated
        @type contourWCS: astWCS.WCS
        @param contourWCS: astWCS.WCS object for the image to be contoured
        @type tag: string
        @param tag: identifying tag for this set of contours
        @type levels: list
        @param levels: sets the contour levels - available options:
            - values: contourLevels=[list of values specifying each level]
            - linear spacing: contourLevels=['linear', min level value, max level value, number
            of levels] - can use "min", "max" to automatically set min, max levels from image data
            - log spacing: contourLevels=['log', min level value, max level value, number of
            levels] - can use "min", "max" to automatically set min, max levels from image data
        @type width: int
        @param width: width of the overlaid contours
        @type color: string
        @param color: color of the overlaid contours, specified by the name of a standard
            matplotlib color, e.g., "black", "white", "cyan"
            etc. (do "help(pylab.colors)" in the Python interpreter to see available options)
        @type smooth: float
        @param smooth: standard deviation (in arcsec) of Gaussian filter for
            pre-smoothing of contour image data (set to 0 for no smoothing)
        @type highAccuracy: bool
        @param highAccuracy: if True, sample every corresponding pixel in each image; otherwise, sample
            every nth pixel, where n = the ratio of the image scales.
        
        """
                
        if self.rgbImage == True:
            backgroundData=self.data[:,:,0]
        else:
            backgroundData=self.data
        contourData=astImages.generateContourOverlay(backgroundData, self.wcs, contourImageData, \
                                              contourWCS, levels, smooth, highAccuracy = highAccuracy)
        
        alreadyGot=False
        for c in self.contourOverlays:
            if c['tag'] == tag:
                c['contourData']=contourData
                c['tag']=tag
                c['color']=color
                c['width']=width
                alreadyGot=True
                
        if alreadyGot == False:
            self.contourOverlays.append({'contourData': contourData, 'tag': tag, 'color': color, \
                                            'width': width})
        self.draw()

    
    def removeContourOverlay(self, tag):
        """Removes the contourOverlay from the ImagePlot corresponding to the tag.
        
        @type tag: string
        @param tag: tag for contour overlay in ImagePlot.contourOverlays to be removed
        
        """
        
        index=0
        for p in self.contourOverlays:
            if p['tag'] == tag:
                self.plotObjects.remove(self.plotObjects[index])
            index=index+1
        self.draw()
        
        
    def addPlotObjects(self, objRAs, objDecs, tag, symbol="circle", size=4.0, width=1.0, color="yellow",                                           
                                    objLabels = None, objLabelSize = 12.0):
        """Add objects with RA, dec coords objRAs, objDecs to the ImagePlot. Only objects that fall within 
        the image boundaries will be plotted.
        
        symbol specifies the type of symbol with which to mark the object in the image. The following
        values are allowed:
            - "circle"
            - "box"
            - "cross"
            - "diamond"
        
        size specifies the diameter in arcsec of the symbol (if plotSymbol == "circle"), or the width
        of the box in arcsec (if plotSymbol == "box")
        
        width specifies the thickness of the symbol lines in pixels
        
        color can be any valid matplotlib color (e.g. "red", "green", etc.)
        
        The objects can be removed from the plot by using removePlotObjects(), and then calling
        draw(). If the ImagePlot already has a set of plotObjects with the same tag, they will be 
        replaced.
        
        @type objRAs: numpy array or list
        @param objRAs: object RA coords in decimal degrees
        @type objDecs: numpy array or list
        @param objDecs: corresponding object Dec. coords in decimal degrees
        @type tag: string
        @param tag: identifying tag for this set of objects
        @type symbol: string
        @param symbol: either "circle", "box", "cross", or "diamond"
        @type size: float
        @param size: size of symbols to plot (radius in arcsec, or width of box)
        @type width: float
        @param width: width of symbols in pixels
        @type color: string
        @param color: any valid matplotlib color string, e.g. "red", "green" etc.
        @type objLabels: list
        @param objLabels: text labels to plot next to objects in figure
        @type objLabelSize: float
        @param objLabelSize: size of font used for object labels (in points)
        
        """
        
        pixCoords=self.wcs.wcs2pix(objRAs, objDecs)
        
        xMax=self.data.shape[1]
        yMax=self.data.shape[0]
        
        if objLabels == None:
            objLabels=[None]*len(objRAs)
            
        xInPlot=[]
        yInPlot=[]
        RAInPlot=[]
        decInPlot=[]
        labelInPlot=[]
        for p, r, d, l in zip(pixCoords, objRAs, objDecs, objLabels):
            if p[0] >= 0 and p[0] < xMax and p[1] >= 0 and p[1] < yMax:
                xInPlot.append(p[0])
                yInPlot.append(p[1])
                RAInPlot.append(r)
                decInPlot.append(d)
                labelInPlot.append(l)
        
        xInPlot=numpy.array(xInPlot)
        yInPlot=numpy.array(yInPlot)
        RAInPlot=numpy.array(RAInPlot)
        decInPlot=numpy.array(decInPlot)
        
        # Size of symbols in pixels in plot - converted from arcsec
        sizePix=(size/3600.0)/self.wcs.getPixelSizeDeg()
        
        alreadyGot=False
        for p in self.plotObjects:
            if p['tag'] == tag:
                p['x']=xInPlot
                p['y']=yInPlot
                p['RA']=RAInPlot
                p['dec']=decInPlot
                p['tag']=tag
                p['objLabels']=objLabels
                p['symbol']=symbol
                p['sizePix']=sizePix
                p['sizeArcSec']=size
                p['width']=width
                p['color']=color
                p['objLabelSize']=objLabelSize
                alreadyGot=True
        
        if alreadyGot == False:
            self.plotObjects.append({'x': xInPlot, 'y': yInPlot, 'RA': RAInPlot, 'dec': decInPlot,
                                'tag': tag, 'objLabels': labelInPlot, 'symbol': symbol, 
                                'sizePix': sizePix, 'width': width, 'color': color,
                                'objLabelSize': objLabelSize, 'sizeArcSec': size})
        self.draw()
        
        
    def removePlotObjects(self, tag):
        """Removes the plotObjects from the ImagePlot corresponding to the tag. The plot must be redrawn
        for the change to take effect.
        
        @type tag: string
        @param tag: tag for set of objects in ImagePlot.plotObjects to be removed
        
        """
        
        index=0
        for p in self.plotObjects:
            if p['tag'] == tag:
                self.plotObjects.remove(self.plotObjects[index])
            index=index+1
        self.draw()
  
        
    def addCompass(self, location, sizeArcSec, color = "white", fontSize = 12, \
                        width = 20.0):
        """Adds a compass to the ImagePlot at the given location ('N', 'NE', 'E', 'SE', 'S', 
        'SW', 'W', or 'NW'). Note these aren't directions on the WCS coordinate grid, they are 
        relative positions on the plot - so N is top centre, NE is top right, SW is bottom right etc.. 
        Alternatively, pixel coordinates (x, y) in the image can be given.
        
        @type location: string or tuple
        @param location: location in the plot where the compass is drawn:
            - string: N, NE, E, SE, S, SW, W or NW
            - tuple: (x, y)
        @type sizeArcSec: float
        @param sizeArcSec: length of the compass arrows on the plot in arc seconds
        @type color: string
        @param color: any valid matplotlib color string
        @type fontSize: float
        @param fontSize: size of font used to label N and E, in points
        @type width: float
        @param width: width of arrows used to mark compass
        
        """
        
        if type(location) == str:
            cRADeg, cDecDeg=self.wcs.getCentreWCSCoords()
            RAMin, RAMax, decMin, decMax=self.wcs.getImageMinMaxWCSCoords()
            westPoint,eastPoint,southPoint,northPoint=astCoords.calcRADecSearchBox(cRADeg, cDecDeg, sizeArcSec/3600.0/2.0)
            sizeRADeg=eastPoint-westPoint
            sizeDecDeg=northPoint-southPoint
            xSizePix=(sizeArcSec/3600.0)/self.wcs.getXPixelSizeDeg()
            ySizePix=(sizeArcSec/3600.0)/self.wcs.getYPixelSizeDeg()
            X=self.data.shape[1]
            Y=self.data.shape[0]
            xBufferPix=0.5*xSizePix
            yBufferPix=0.5*ySizePix
            cx, cy=self.wcs.wcs2pix(cRADeg, cDecDeg)
            foundLocation=False
            x=cy
            y=cx
            if self.wcs.isFlipped() == False:              
                if location.find("N") != -1:
                    y=Y-2*yBufferPix
                    foundLocation=True
                if location.find("S") != -1:
                    y=yBufferPix
                    foundLocation=True
                if location.find("E") != -1:
                    x=xBufferPix*2
                    foundLocation=True
                if location.find("W") != -1:
                    x=X-xBufferPix
                    foundLocation=True
            else:
                if location.find("S") != -1:
                    y=Y-2*yBufferPix
                    foundLocation=True
                if location.find("N") != -1:
                    y=yBufferPix
                    foundLocation=True
                if location.find("W") != -1:
                    x=xBufferPix*2
                    foundLocation=True
                if location.find("E") != -1:
                    x=X-xBufferPix
                    foundLocation=True
            if foundLocation == False:
                raise Exception("didn't understand location string for scale bar (should be e.g. N, S, E, W).")
            RADeg, decDeg=self.wcs.pix2wcs(x, y)
        elif type(location) == tuple or type(location) == list:
            x, y=location
            RADeg, decDeg=self.wcs.pix2wcs(x, y)
        else:
            raise Exception("didn't understand location for scale bar - should be string or tuple.")
        
        alreadyGot=False
        for p in self.plotObjects:
            if p['tag'] == "compass":
                p['x']=[x]
                p['y']=[y]
                p['RA']=[RADeg]
                p['dec']=[decDeg]
                p['tag']="compass"
                p['objLabels']=[None]
                p['symbol']="compass"
                p['sizeArcSec']=sizeArcSec
                p['width']=width
                p['color']=color
                p['objLabelSize']=fontSize
                alreadyGot=True
        
        if alreadyGot == False:
            self.plotObjects.append({'x': [x], 'y': [y], 'RA': [RADeg], 'dec': [decDeg],
                                'tag': "compass", 'objLabels': [None], 'symbol': "compass", 
                                'width': width, 'color': color,
                                'objLabelSize': fontSize, 'sizeArcSec': sizeArcSec})
        self.draw()


    def addScaleBar(self, location, sizeArcSec, color = "white", fontSize = 12, \
                        width = 20.0):
        """Adds a scale bar to the ImagePlot at the given location ('N', 'NE', 'E', 'SE', 'S', 
        'SW', 'W', or 'NW'). Note these aren't directions on the WCS coordinate grid, they are 
        relative positions on the plot - so N is top centre, NE is top right, SW is bottom right etc.. 
        Alternatively, pixel coordinates (x, y) in the image can be given.
        
        @type location: string or tuple
        @param location: location in the plot where the compass is drawn:
            - string: N, NE, E, SE, S, SW, W or NW
            - tuple: (x, y)
        @type sizeArcSec: float
        @param sizeArcSec: scale length to indicate on the plot in arc seconds
        @type color: string
        @param color: any valid matplotlib color string
        @type fontSize: float
        @param fontSize: size of font used to label N and E, in points
        @type width: float
        @param width: width of arrow used to mark scale
        
        """
        
        # Work out where the scale bar is going in WCS coords from the relative location given
        if type(location) == str:
            cRADeg, cDecDeg=self.wcs.getCentreWCSCoords()
            RAMin, RAMax, decMin, decMax=self.wcs.getImageMinMaxWCSCoords()
            westPoint,eastPoint,southPoint,northPoint=astCoords.calcRADecSearchBox(cRADeg, cDecDeg, sizeArcSec/3600.0/2.0)
            sizeRADeg=eastPoint-westPoint
            sizeDecDeg=northPoint-southPoint
            xSizePix=(sizeArcSec/3600.0)/self.wcs.getXPixelSizeDeg()
            ySizePix=(sizeArcSec/3600.0)/self.wcs.getYPixelSizeDeg()
            X=self.data.shape[1]
            Y=self.data.shape[0]
            xBufferPix=0.6*ySizePix
            yBufferPix=0.05*Y
            cx, cy=self.wcs.wcs2pix(cRADeg, cDecDeg)
            foundLocation=False
            x=cy
            y=cx
            if self.wcs.isFlipped() == False:
                if location.find("N") != -1:
                    y=Y-1.5*yBufferPix
                    foundLocation=True
                if location.find("S") != -1:
                    y=yBufferPix
                    foundLocation=True
                if location.find("E") != -1:
                    x=xBufferPix
                    foundLocation=True
                if location.find("W") != -1:
                    x=X-xBufferPix
                    foundLocation=True
            else:
                if location.find("S") != -1:
                    y=Y-1.5*yBufferPix
                    foundLocation=True
                if location.find("N") != -1:
                    y=yBufferPix
                    foundLocation=True
                if location.find("W") != -1:
                    x=xBufferPix
                    foundLocation=True
                if location.find("E") != -1:
                    x=X-xBufferPix
                    foundLocation=True
            if foundLocation == False:
                raise Exception("didn't understand location string for scale bar (should be e.g. N, S, E, W).")
            RADeg, decDeg=self.wcs.pix2wcs(x, y)
        elif type(location) == tuple or type(location) == list:
            x, y=location
            RADeg, decDeg=self.wcs.pix2wcs(x, y)
        else:
            raise Exception("didn't understand location for scale bar - should be string or tuple.")
        
        alreadyGot=False
        for p in self.plotObjects:
            if p['tag'] == "scaleBar":
                p['x']=[x]
                p['y']=[y]
                p['RA']=[RADeg]
                p['dec']=[decDeg]
                p['tag']="scaleBar"
                p['objLabels']=[None]
                p['symbol']="scaleBar"
                p['sizeArcSec']=sizeArcSec
                p['width']=width
                p['color']=color
                p['objLabelSize']=fontSize
                alreadyGot=True
        
        if alreadyGot == False:
            self.plotObjects.append({'x': [x], 'y': [y], 'RA': [RADeg], 'dec': [decDeg],
                                'tag': "scaleBar", 'objLabels': [None], 'symbol': "scaleBar", 
                                'width': width, 'color': color,
                                'objLabelSize': fontSize, 'sizeArcSec': sizeArcSec})
        self.draw()
                                

    def calcWCSAxisLabels(self, axesLabels = "decimal"):
        """This function calculates the positions of coordinate labels for the RA and Dec axes of the 
        ImagePlot. The tick steps are calculated automatically unless self.RATickSteps,
        self.decTickSteps are set to values other than "auto" (see L{ImagePlot.__init__}). 
        
        The ImagePlot must be redrawn for changes to be applied.
        
        @type axesLabels: string
        @param axesLabels: either "sexagesimal" (for H:M:S, D:M:S), "decimal" (for decimal degrees),
        or None for no coordinate axes labels
        
        """
        
        # Label equinox on axes
        equinox=self.wcs.getEquinox()
        if equinox<1984:
            equinoxLabel="B"+str(int(equinox))
        else:
            equinoxLabel="J"+str(int(equinox))
           
        self.axesLabels=axesLabels
        
        ticsDict=self.getTickSteps()
        
        # Manual override - note: no minor tick marks anymore, but may want to bring them back
        if self.RATickSteps != "auto":
            ticsDict['major']['RA']=self.RATickSteps
        if self.decTickSteps != "auto":
            ticsDict['major']['dec']=self.decTickSteps
        
        RALocs=[]
        decLocs=[]
        RALabels=[]
        decLabels=[]
        key="major"
        #for key in ticsDict.keys(): # key is major or minor
        if self.axesLabels == "sexagesimal":
            self.RAAxisLabel="R.A. ("+equinoxLabel+")"
            self.decAxisLabel="Dec. ("+equinoxLabel+")"
            RADegStep=ticsDict[key]['RA']['deg']
            decDegStep=ticsDict[key]['dec']['deg']
        elif self.axesLabels == "decimal":
            self.RAAxisLabel="R.A. Degrees ("+equinoxLabel+")"
            self.decAxisLabel="Dec. Degrees ("+equinoxLabel+")"
            RADegStep=ticsDict[key]['RA']
            decDegStep=ticsDict[key]['dec']
        else:
            raise Exception("axesLabels must be either 'sexagesimal' or 'decimal'")
        
        xArray=numpy.arange(0, self.data.shape[1], 1)
        yArray=numpy.arange(0, self.data.shape[0], 1)
        xWCS=self.wcs.pix2wcs(xArray, numpy.zeros(xArray.shape[0], dtype=float))
        yWCS=self.wcs.pix2wcs(numpy.zeros(yArray.shape[0], dtype=float), yArray)
        xWCS=numpy.array(xWCS)
        yWCS=numpy.array(yWCS)
        ras=xWCS[:,0]
        decs=yWCS[:,1]
        RAEdges=numpy.array([ras[0], ras[-1]])
        RAMin=RAEdges.min()
        RAMax=RAEdges.max()
        decMin=decs.min()
        decMax=decs.max()
        
        # Work out if wrapped around
        midRAPix, midDecPix=self.wcs.wcs2pix((RAEdges[1]+RAEdges[0])/2.0, (decMax+decMin)/2.0)
        if midRAPix < 0 or midRAPix > self.wcs.header['NAXIS1']:
            wrappedRA=True
        else:
            wrappedRA=False
            
        # Note RA, dec work in opposite sense below because E at left
        if ras[1] < ras[0]:
            self.flipXAxis=False
            ra2x=interpolate.interp1d(ras[::-1], xArray[::-1], kind='linear')
        else:
            self.flipXAxis=True
            ra2x=interpolate.interp1d(ras, xArray, kind='linear')
        if decs[1] < decs[0]:
            self.flipYAxis=True
            dec2y=interpolate.interp1d(decs[::-1], yArray[::-1], kind='linear')
        else:
            self.flipYAxis=False
            dec2y=interpolate.interp1d(decs, yArray, kind='linear')
        
        if wrappedRA == False:
            RAPlotMin=RADegStep*math.modf(RAMin/RADegStep)[1]
            RAPlotMax=RADegStep*math.modf(RAMax/RADegStep)[1]
            if RAPlotMin < RAMin:
                RAPlotMin=RAPlotMin+RADegStep
            if RAPlotMax >= RAMax:
                RAPlotMax=RAPlotMax-RADegStep
            RADegs=numpy.arange(RAPlotMin, RAPlotMax+0.0001, RADegStep)
        else:
            RAPlotMin=RADegStep*math.modf(RAMin/RADegStep)[1]
            RAPlotMax=RADegStep*math.modf(RAMax/RADegStep)[1]
            if RAPlotMin > RAMin:
                RAPlotMin=RAPlotMin-RADegStep
            if RAPlotMax <= RAMax:
                RAPlotMax=RAPlotMax+RADegStep
            for i in range(ras.shape[0]):
                if ras[i] >= RAMax and ras[i] <= 360.0:
                    ras[i]=ras[i]-360.0
            if ras[1] < ras[0]:
                ra2x=interpolate.interp1d(ras[::-1], xArray[::-1], kind='linear')
            else:
                ra2x=interpolate.interp1d(ras, xArray, kind='linear')
            RADegs=numpy.arange(RAPlotMin, RAPlotMax-360.0-0.0001, -RADegStep)

        decPlotMin=decDegStep*math.modf(decMin/decDegStep)[1]
        decPlotMax=decDegStep*math.modf(decMax/decDegStep)[1]
        if decPlotMin < decMin:
            decPlotMin=decPlotMin+decDegStep
        if decPlotMax >= decMax:
            decPlotMax=decPlotMax-decDegStep
        decDegs=numpy.arange(decPlotMin, decPlotMax+0.0001, decDegStep)
        
        if key == "major":
            if axesLabels == "sexagesimal":
                for r in RADegs:
                    if r < 0:
                        r=r+360.0
                    h, m, s=astCoords.decimal2hms(r, ":").split(":")
                    hInt=int(round(float(h)))
                    if ticsDict[key]['RA']['unit'] == 'h' and (60.0-float(m)) < 0.01: # Check for rounding error
                        hInt=hInt+1
                    if hInt < 10:
                        hString="0"+str(hInt)
                    else:
                        hString=str(hInt)
                    mInt=int(round(float(m)))
                    if ticsDict[key]['RA']['unit'] == 'm' and (60.0-float(s)) < 0.01: # Check for rounding error
                        mInt=mInt+1
                    if mInt < 10:
                        mString="0"+str(mInt)
                    else:
                        mString=str(mInt)
                    sInt=int(round(float(s)))
                    if sInt < 10:
                        sString="0"+str(sInt)
                    else:
                        sString=str(sInt)
                    if ticsDict[key]['RA']['unit'] == 'h':
                        rString=hString+"$^{\sf{h}}$"
                    elif ticsDict[key]['RA']['unit'] == 'm':
                        rString=hString+"$^{\sf{h}}$"+mString+"$^{\sf{m}}$"
                    else:
                        rString=hString+"$^{\sf{h}}$"+mString+"$^{\sf{m}}$"+sString+"$^{\sf{s}}$"
                    RALabels.append(rString)
                for D in decDegs:
                    d, m, s=astCoords.decimal2dms(D, ":").split(":")
                    dInt=int(round(float(d)))
                    if ticsDict[key]['dec']['unit'] == 'd' and (60.0-float(m)) < 0.01: # Check for rounding error
                        dInt=dInt+1
                    if dInt < 10 and dInt >= 0 and D > 0:
                        dString="+0"+str(dInt)
                    elif dInt > -10 and dInt <= 0 and D < 0:
                        dString="-0"+str(abs(dInt))
                    elif dInt >= 10:
                        dString="+"+str(dInt)
                    else:
                        dString=str(dInt)
                    mInt=int(round(float(m)))
                    if ticsDict[key]['dec']['unit'] == 'm' and (60.0-float(s)) < 0.01: # Check for rounding error
                        mInt=mInt+1
                    if mInt < 10:
                        mString="0"+str(mInt)
                    else:
                        mString=str(mInt)
                    sInt=int(round(float(s)))
                    if sInt < 10:
                        sString="0"+str(sInt)
                    else:
                        sString=str(sInt)
                    if ticsDict[key]['dec']['unit'] == 'd':
                        dString=dString+DEG
                    elif ticsDict[key]['dec']['unit'] == 'm':
                        dString=dString+DEG+mString+PRIME
                    else:
                        dString=dString+DEG+mString+PRIME+sString+DOUBLE_PRIME               
                    decLabels.append(dString)
            elif axesLabels == "decimal":
                                
                if wrappedRA == False:
                    RALabels=RALabels+RADegs.tolist()
                else:
                    nonNegativeLabels=[]
                    for r in RADegs:
                        if r < 0:
                            r=r+360.0
                        nonNegativeLabels.append(r)
                    RALabels=RALabels+nonNegativeLabels
                decLabels=decLabels+decDegs.tolist()
                
                # Format RALabels, decLabels to same number of d.p.
                dpNumRA=len(str(ticsDict['major']['RA']).split(".")[-1])
                dpNumDec=len(str(ticsDict['major']['dec']).split(".")[-1])
                for i in range(len(RALabels)):
                    fString="%."+str(dpNumRA)+"f"
                    RALabels[i]=fString % (RALabels[i])
                for i in range(len(decLabels)):
                    fString="%."+str(dpNumDec)+"f"
                    decLabels[i]=fString % (decLabels[i])                                
        
        if key == 'minor':
            RALabels=RALabels+RADegs.shape[0]*['']
            decLabels=decLabels+decDegs.shape[0]*['']
        
        RALocs=RALocs+ra2x(RADegs).tolist()
        decLocs=decLocs+dec2y(decDegs).tolist()
            
        self.ticsRA=[RALocs, RALabels]
        self.ticsDec=[decLocs, decLabels]
        

    def save(self, fileName):
        """Saves the ImagePlot in any format that matplotlib can understand, as determined from the 
        fileName extension.
        
        @type fileName: string
        @param fileName: path where plot will be written
        
        """
        
        pylab.draw()
        pylab.savefig(fileName)
        
        
    def getTickSteps(self):
        """Chooses the appropriate WCS coordinate tick steps for the plot based on its size.
        Whether the ticks are decimal or sexagesimal is set by self.axesLabels.
        
        Note: minor ticks not used at the moment.
        
        @rtype: dictionary
        @return: tick step sizes for major, minor plot ticks, in format {'major', 'minor'}
                
        """
        
        # Aim for 5 major tick marks on a plot
        xArray=numpy.arange(0, self.data.shape[1], 1)
        yArray=numpy.arange(0, self.data.shape[0], 1)
        xWCS=self.wcs.pix2wcs(xArray, numpy.zeros(xArray.shape[0], dtype=float))
        yWCS=self.wcs.pix2wcs(numpy.zeros(yArray.shape[0], dtype=float), yArray)
        xWCS=numpy.array(xWCS)
        yWCS=numpy.array(yWCS)
        ras=xWCS[:,0]
        decs=yWCS[:,1]
        RAEdges=numpy.array([ras[0], ras[-1]])
        RAMin=RAEdges.min()
        RAMax=RAEdges.max()
        decMin=decs.min()
        decMax=decs.max()
        
        # Work out if wrapped around
        midRAPix, midDecPix=self.wcs.wcs2pix((RAEdges[1]+RAEdges[0])/2.0, (decMax+decMin)/2.0)
        if midRAPix < 0 or midRAPix > self.wcs.header['NAXIS1']:
            wrappedRA=True
        else:
            wrappedRA=False
        if wrappedRA == False:
            RAWidthDeg=RAMax-RAMin
        else:
            RAWidthDeg=(360.0-RAMax)+RAMin
        decHeightDeg=decMax-decMin

        ticsDict={}
        ticsDict['major']={}
        ticsDict['minor']={}
        if self.axesLabels == "sexagesimal":
            
            matchIndex = 0
            for i in range(len(RA_TICK_STEPS)):
                if RAWidthDeg/2.5 > RA_TICK_STEPS[i]['deg']:
                    matchIndex = i
            
            ticsDict['major']['RA']=RA_TICK_STEPS[matchIndex]
            ticsDict['minor']['RA']=RA_TICK_STEPS[matchIndex-1]

            matchIndex = 0
            for i in range(len(DEC_TICK_STEPS)):
                if decHeightDeg/2.5 > DEC_TICK_STEPS[i]['deg']:
                    matchIndex = i
                                
            ticsDict['major']['dec']=DEC_TICK_STEPS[matchIndex]
            ticsDict['minor']['dec']=DEC_TICK_STEPS[matchIndex-1]
            
            return ticsDict
            
        elif self.axesLabels == "decimal":
            
            matchIndex = 0
            for i in range(len(DECIMAL_TICK_STEPS)):
                if RAWidthDeg/2.5 > DECIMAL_TICK_STEPS[i]:
                    matchIndex = i
            
            ticsDict['major']['RA']=DECIMAL_TICK_STEPS[matchIndex]
            ticsDict['minor']['RA']=DECIMAL_TICK_STEPS[matchIndex-1]
            
            matchIndex = 0
            for i in range(len(DECIMAL_TICK_STEPS)):
                if decHeightDeg/2.5 > DECIMAL_TICK_STEPS[i]:
                    matchIndex = i
                    
            ticsDict['major']['dec']=DECIMAL_TICK_STEPS[matchIndex]
            ticsDict['minor']['dec']=DECIMAL_TICK_STEPS[matchIndex-1]
            
            return ticsDict
        
        else:
            raise Exception("axesLabels must be either 'sexagesimal' or 'decimal'")

