Matplotlib绘图用滚轮缩放

Question

当光标悬停在matplotlib图上时,是否可以绑定滚轮来放大/缩小？

Answer 1

这应该工作.滚动时,它会将图形重新定位在指针位置上.

import matplotlib.pyplot as plt


def zoom_factory(ax,base_scale = 2.):
    def zoom_fun(event):
        # get the current x and y limits
        cur_xlim = ax.get_xlim()
        cur_ylim = ax.get_ylim()
        cur_xrange = (cur_xlim[1] - cur_xlim[0])*.5
        cur_yrange = (cur_ylim[1] - cur_ylim[0])*.5
        xdata = event.xdata # get event x location
        ydata = event.ydata # get event y location
        if event.button == 'up':
            # deal with zoom in
            scale_factor = 1/base_scale
        elif event.button == 'down':
            # deal with zoom out
            scale_factor = base_scale
        else:
            # deal with something that should never happen
            scale_factor = 1
            print event.button
        # set new limits
        ax.set_xlim([xdata - cur_xrange*scale_factor,
                     xdata + cur_xrange*scale_factor])
        ax.set_ylim([ydata - cur_yrange*scale_factor,
                     ydata + cur_yrange*scale_factor])
        plt.draw() # force re-draw

    fig = ax.get_figure() # get the figure of interest
    # attach the call back
    fig.canvas.mpl_connect('scroll_event',zoom_fun)

    #return the function
    return zoom_fun

假设你有一个轴对象 ax

 ax.plot(range(10))
 scale = 1.5
 f = zoom_factory(ax,base_scale = scale)

可选参数base_scale允许您将比例因子设置为您想要的.

确保你保留一份副本f.回调使用弱参考,所以如果你不保留f它的副本可能是垃圾收集.

在写完这个答案后,我认为这实际上非常有用,并把它放在一个要点

Answer 2

谢谢大家,这些例子非常有帮助.我不得不做一些改变来使用散点图,我添加了一个左按钮拖动平移.希望有人会觉得这很有用.

from matplotlib.pyplot import figure, show
import numpy

class ZoomPan:
    def __init__(self):
        self.press = None
        self.cur_xlim = None
        self.cur_ylim = None
        self.x0 = None
        self.y0 = None
        self.x1 = None
        self.y1 = None
        self.xpress = None
        self.ypress = None


    def zoom_factory(self, ax, base_scale = 2.):
        def zoom(event):
            cur_xlim = ax.get_xlim()
            cur_ylim = ax.get_ylim()

            xdata = event.xdata # get event x location
            ydata = event.ydata # get event y location

            if event.button == 'down':
                # deal with zoom in
                scale_factor = 1 / base_scale
            elif event.button == 'up':
                # deal with zoom out
                scale_factor = base_scale
            else:
                # deal with something that should never happen
                scale_factor = 1
                print event.button

            new_width = (cur_xlim[1] - cur_xlim[0]) * scale_factor
            new_height = (cur_ylim[1] - cur_ylim[0]) * scale_factor

            relx = (cur_xlim[1] - xdata)/(cur_xlim[1] - cur_xlim[0])
            rely = (cur_ylim[1] - ydata)/(cur_ylim[1] - cur_ylim[0])

            ax.set_xlim([xdata - new_width * (1-relx), xdata + new_width * (relx)])
            ax.set_ylim([ydata - new_height * (1-rely), ydata + new_height * (rely)])
            ax.figure.canvas.draw()

        fig = ax.get_figure() # get the figure of interest
        fig.canvas.mpl_connect('scroll_event', zoom)

        return zoom

    def pan_factory(self, ax):
        def onPress(event):
            if event.inaxes != ax: return
            self.cur_xlim = ax.get_xlim()
            self.cur_ylim = ax.get_ylim()
            self.press = self.x0, self.y0, event.xdata, event.ydata
            self.x0, self.y0, self.xpress, self.ypress = self.press

        def onRelease(event):
            self.press = None
            ax.figure.canvas.draw()

        def onMotion(event):
            if self.press is None: return
            if event.inaxes != ax: return
            dx = event.xdata - self.xpress
            dy = event.ydata - self.ypress
            self.cur_xlim -= dx
            self.cur_ylim -= dy
            ax.set_xlim(self.cur_xlim)
            ax.set_ylim(self.cur_ylim)

            ax.figure.canvas.draw()

        fig = ax.get_figure() # get the figure of interest

        # attach the call back
        fig.canvas.mpl_connect('button_press_event',onPress)
        fig.canvas.mpl_connect('button_release_event',onRelease)
        fig.canvas.mpl_connect('motion_notify_event',onMotion)

        #return the function
        return onMotion


fig = figure()

ax = fig.add_subplot(111, xlim=(0,1), ylim=(0,1), autoscale_on=False)

ax.set_title('Click to zoom')
x,y,s,c = numpy.random.rand(4,200)
s *= 200

ax.scatter(x,y,s,c)
scale = 1.1
zp = ZoomPan()
figZoom = zp.zoom_factory(ax, base_scale = scale)
figPan = zp.pan_factory(ax)
show()

Answer 3

def zoom(self, event, factor):
    curr_xlim = self.ax.get_xlim()
    curr_ylim = self.ax.get_ylim()

    new_width = (curr_xlim[1]-curr_ylim[0])*factor
    new_height= (curr_xlim[1]-curr_ylim[0])*factor

    relx = (curr_xlim[1]-event.xdata)/(curr_xlim[1]-curr_xlim[0])
    rely = (curr_ylim[1]-event.ydata)/(curr_ylim[1]-curr_ylim[0])

    self.ax.set_xlim([event.xdata-new_width*(1-relx),
                event.xdata+new_width*(relx)])
    self.ax.set_ylim([event.ydata-new_width*(1-rely),
                        event.ydata+new_width*(rely)])
    self.draw()

略微更改代码的目的是跟踪光标相对于新缩放中心的位置。这样，如果您在中心以外的其他位置放大和缩小图片，则您将保持在同一点。