Question

I am writing a simple digital image processing program. To do this I have embedded a mpl widget in my qt application. The user can perform some simple analysis on the image such as box car filter, FFT etc. Every thing is working fine until I would like to switch from displaying an image to displaying a plot.

If I display a plot first, the axis are fine (see bottom plot in image). But if I display an image first, followed by a plot (top plot in image), the scale compresses.

https://picasaweb.google.com/105163945296073520628/Temp <– sorry I can’t post images yet

The code is hosted here https://code.launchpad.net/~marrabld/pymi/trunk

I am using imshow() to display the image. and plot(x,y) for the plots.

This is the main update method

def updateImage(self):
    self.ui.mplWidget.canvas.PlotTitle = self.plotTitle
    self.ui.mplWidget.canvas.xtitle = self.xTitle
    self.ui.mplWidget.canvas.ytitle = self.yTitle
    #self.ui.mplWidget.canvas.ax.visible(False)

    self.ui.mplWidget.canvas.format_labels()
    if self.projectProperty == globals.IMAGE:
        if self.lastProjectProperty == globals.PLOT:
            self.myImage = imageFuncs.basic(self.imageFileName)

        self.imPlot = self.ui.mplWidget.canvas.ax.imshow(self.myImage.image,cmap=matplotlib.cm.gray,origin='upper')

    elif self.projectProperty == globals.PLOT:

        if self.lastProjectProperty == globals.IMAGE: # we need to reload the GUI

            self.ui.mplWidget.canvas.ax.hold(False) 

        self.ui.mplWidget.canvas.ax.plot(self.xData,self.yData)

    self.ui.mplWidget.canvas.draw()

And the mpl widget I am using

#!/usr/bin/env python
from PyQt4.QtCore import *
from PyQt4.QtGui import *

from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
#from matplotlib.backends.backend_qt4 import NavigationToolbar2QT as NavigationToolbar
from matplotlib.backend_bases import NavigationToolbar2

from matplotlib.figure import Figure
from matplotlib import rc

import numpy as N

class MyMplCanvas(FigureCanvas):
    def __init__(self, parent=None, width = 10, height = 12, dpi = 125, sharex = None, sharey = None):

            rc('text', usetex=True)
            rc('font', family='sans-serif')
            rc('legend',fontsize='small' )
            rc('legend',shadow='true')

            self.fig = Figure(figsize = (width, height), dpi=dpi, facecolor = '#FFFFFF')

            self.ax = self.fig.add_subplot(111, sharex = sharex, sharey = sharey)
            self.fig.subplots_adjust(left=0.15, bottom=0.15, right=0.9, top=0.9)
            self.fig.add_axes(yscale='symlog')
            self.xtitle=r"x-Axis"
            self.ytitle=r"y-Axis"
            self.PlotTitle = r"Title"
            self.grid_status = True
            self.xaxis_style = 'linear'
            self.yaxis_style = 'linear'
            #self.fig.yscale = 'log'
            self.format_labels()
            self.ax.hold(True)
            FigureCanvas.__init__(self, self.fig)
            #self.fc = FigureCanvas(self.fig)
            #FigureCanvas.setSizePolicy(self,
             #       QSizePolicy.Expanding,
              #      QSizePolicy.Expanding)
            FigureCanvas.updateGeometry(self)

    def format_labels(self):
            self.ax.set_title(self.PlotTitle)
            self.ax.title.set_fontsize(5)
            self.ax.set_xlabel(self.xtitle, fontsize = 4)
            self.ax.set_ylabel(self.ytitle, fontsize = 4)
            labels_x = self.ax.get_xticklabels()
            labels_y = self.ax.get_yticklabels()

            for xlabel in labels_x:
                    xlabel.set_fontsize(4)
            for ylabel in labels_y:
                    ylabel.set_fontsize(4)
                    ylabel.set_color('b')

    def sizeHint(self):
            w, h = self.get_width_height()
            return QSize(w, h)

    def minimumSizeHint(self):
            return QSize(10, 10)

    def sizeHint(self):
            w, h = self.get_width_height()
            return QSize(w, h)

    def minimumSizeHint(self):
            return QSize(10, 10)




    #mouseClick = pyqtProperty("QPoint",mouseClick,click)






class mplWidget(QWidget):
    def __init__(self, parent = None):
            QWidget.__init__(self, parent)
            self.canvas = MyMplCanvas()
            #self.toolbar = MyNavigationToolbar(self.canvas, self.canvas, direction = 'v')
            self.hbox = QHBoxLayout()
            #self.hbox.addWidget(self.toolbar)
            self.hbox.addWidget(self.canvas)
            self.setLayout(self.hbox)

    def savePlot(self,filePath):
            self.canvas.fig.savefig(filePath)

    def setLegend(self,handle, label):
            self.canvas.fig.legend(handle,label,'upper right')

    def clearPlot(self):
            self.canvas.fig.clear()

            width = 10
            height = 12
            dpi = 125
            sharex = None
            sharey = None

            self.canvas.fig = Figure(figsize = (width, height), dpi=dpi, facecolor = '#FFFFFF')

            self.canvas.ax = self.canvas.fig.add_subplot(111, sharex = sharex, sharey = sharey)
            self.canvas.fig.subplots_adjust(left=0.15, bottom=0.15, right=0.9, top=0.9)
            self.canvas.fig.add_axes(yscale='symlog')
            self.canvas.xtitle=r"x-Axis"
            self.canvas.ytitle=r"y-Axis"
            self.canvas.PlotTitle = r"Title"
            self.canvas.grid_status = True
            self.canvas.xaxis_style = 'linear'
            self.canvas.yaxis_style = 'linear'
            #self.fig.yscale = 'log'
            self.canvas.format_labels()
            self.canvas.ax.hold(True)

            FigureCanvas.__init__(self.canvas, self.canvas.fig)
            #self.fc = FigureCanvas(self.fig)
            FigureCanvas.setSizePolicy(self,
                    QSizePolicy.Expanding,
                    QSizePolicy.Expanding)
            FigureCanvas.updateGeometry(self)

Any Help would be greatly appreciated.

Answer 1

you can use aspect parameter of imshow() to adjust the ratio between the height & weight:

from pylab import *
a = np.zeros((100,10)) # height=100, weight=10
subplot(211)
imshow(a)  # ratio = 10
subplot(212)
imshow(a, aspect=0.1) # ratio = 1
show()

but it will stretch the image.

or you can use xlim(), ylim() the set the range of x-y axis.

imshow(a)
xlim(-50,50)

EDIT:

imshow() will set the aspect property of axe to “equal”. you need reset it before calling plot():

self.ui.mplWidget.canvas.ax.set_aspect("auto")
self.ui.mplWidget.canvas.ax.plot(self.xData,self.yData)