Python 如何使用matplotlib在绘图的角落插入小图像？
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How to insert a small image on the corner of a plot with matplotlib?
提问by pleasedontbelong
What I want is really simple: I have a small image file called "logo.png" that I want to display on the upper left corner of my plots. But you can't find any example of that in the matplotlib examples gallery.
我想要的非常简单：我有一个名为“logo.png”的小图像文件，我想将其显示在绘图的左上角。但是您在 matplotlib 示例库中找不到任何示例。
I'm using django, and my code is something like this:
我正在使用 django，我的代码是这样的：
def get_bars(request)
...
fig = Figure(facecolor='#F0F0F0',figsize=(4.6,4))
...
ax1 = fig.add_subplot(111,ylabel="Valeur",xlabel="Code",autoscale_on=True)
ax1.bar(ind,values,width=width, color='#FFCC00',edgecolor='#B33600',linewidth=1)
...
canvas = FigureCanvas(fig)
response = HttpResponse(content_type='image/png')
canvas.print_png(response)
return response
采纳答案by Joe Kington
If you want the image at the corner of your actual figure (rather than the corner of your axis), look into figimage.
如果您希望图像位于实际图形的角落（而不是轴的角落），请查看figimage.
Perhaps something like this? (using PIL to read the image):
也许像这样？（使用 PIL 读取图像）：
import matplotlib.pyplot as plt
import Image
import numpy as np
im = Image.open('/home/jofer/logo.png')
height = im.size[1]
# We need a float array between 0-1, rather than
# a uint8 array between 0-255
im = np.array(im).astype(np.float) / 255
fig = plt.figure()
plt.plot(np.arange(10), 4 * np.arange(10))
# With newer (1.0) versions of matplotlib, you can
# use the "zorder" kwarg to make the image overlay
# the plot, rather than hide behind it... (e.g. zorder=10)
fig.figimage(im, 0, fig.bbox.ymax - height)
# (Saving with the same dpi as the screen default to
# avoid displacing the logo image)
fig.savefig('/home/jofer/temp.png', dpi=80)
plt.show()
Another option, if you'd like to have the image be a fixed fraction of the figure's width/height is to create a "dummy" axes and place the image in it with imshow. This way the image's size and position is independent of DPI and the figure's absolute size:
另一种选择，如果您想让图像成为图形宽度/高度的固定分数，则创建一个“虚拟”轴并将图像放在其中imshow。这样图像的大小和位置就独立于 DPI 和图形的绝对大小：
import matplotlib.pyplot as plt
from matplotlib.cbook import get_sample_data
im = plt.imread(get_sample_data('grace_hopper.jpg'))
fig, ax = plt.subplots()
ax.plot(range(10))
# Place the image in the upper-right corner of the figure
#--------------------------------------------------------
# We're specifying the position and size in _figure_ coordinates, so the image
# will shrink/grow as the figure is resized. Remove "zorder=-1" to place the
# image in front of the axes.
newax = fig.add_axes([0.8, 0.8, 0.2, 0.2], anchor='NE', zorder=-1)
newax.imshow(im)
newax.axis('off')
plt.show()
