Replace Matplotlib legend's labels with image

问题:

I would like to use image instead of labels in the legend.

For example, I draw 2 lines and show a legend :

import matplotlib.pyplot as plt
plt.plot([1,2],label="first_image")
plt.plot([2,1],label="second_image")
plt.legend()
plot.show()

But I would like to have something like this :

Note that this is not a duplicate of Insert image in matplotlib legend , My issue is "change the label into an image", while the other is "change the legend's symbol into an image"

回答1:

The concept for creating an image in a legend is already presented in this question (Insert image in matplotlib legend) where an image is used as an artist for a legend entry.

In case you want a line handle and an image in the legend, the idea would be to create a handle that consists of both of them, positionned next to each other. The only problem is then to fine tune the parameters such that this looks appealing.

import matplotlib.pyplot as plt
import matplotlib.lines
from matplotlib.transforms import Bbox, TransformedBbox
from matplotlib.legend_handler import HandlerBase
from matplotlib.image import BboxImage

class HandlerLineImage(HandlerBase):

    def __init__(self, path, space=15, offset = 10 ):
        self.space=space
        self.offset=offset
        self.image_data = plt.imread(path)        
        super(HandlerLineImage, self).__init__()

    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize, trans):

        l = matplotlib.lines.Line2D([xdescent+self.offset,xdescent+(width-self.space)/3.+self.offset],
                                     [ydescent+height/2., ydescent+height/2.])
        l.update_from(orig_handle)
        l.set_clip_on(False)
        l.set_transform(trans)

        bb = Bbox.from_bounds(xdescent +(width+self.space)/3.+self.offset,
                              ydescent,
                              height*self.image_data.shape[1]/self.image_data.shape[0],
                              height)

        tbb = TransformedBbox(bb, trans)
        image = BboxImage(tbb)
        image.set_data(self.image_data)

        self.update_prop(image, orig_handle, legend)
        return [l,image]


plt.figure(figsize=(4.8,3.2))
line,  = plt.plot([1,2],[1.5,3], color="#1f66e0", lw=1.3)
line2,  = plt.plot([1,2],[1,2], color="#efe400", lw=1.3)
plt.ylabel("Flower power")

plt.legend([line, line2], ["", ""],
   handler_map={ line: HandlerLineImage("icon1.png"), line2: HandlerLineImage("icon2.png")}, 
   handlelength=2, labelspacing=0.0, fontsize=36, borderpad=0.15, loc=2, 
    handletextpad=0.2, borderaxespad=0.15)

plt.show()