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python_matplotlib

  • 複数の図(subplot)の全体についてタイトルをつける:
plt.suptitle
  • 複数の図(subplot)どうしの間隔を調整:
plt.subplots_adjust(wspace=0.4, hspace=0.6)
  • 新規ウィンドウ(複数の図を別々のウィンドウで出す時) / Display two images in different windows
plt.imshow(im1)
plt.figure()    # <---- This is the key!!!
plt.imshow(im2)
plt.show()
  • plt.show()せずにウィンドウをキャッシュから消す:
plt.close()
  • RGB画像を出したいときは, データをnp.arrayでastype(uint8)にすること。uint16やfloatでは色が変になる。たとえvmin, vmaxを指定しても。

drawing a map (plt.imshow)

  • change aspect (narrower, for example):
plt.imshow(img, aspect=2) # ... vertical length is 2 times of horizontal.

drawing a RGB map

plt.imshow(x[:,:,[4,2,1]]/np.max(x[:,:,[4,2,1]]))
  • Here, x is np.ndarray with a shape of (lines, pixels, bands).
  • The data must be represented by real numbers ranging from 0 to 1. No "int" or "uint", please!
  • By setting the third index as [4, 2, 1], the band 4, band 2, and band 1 are assigned to R, G, B, respectively.

Label

  • give title of the picture:
plt.title("title")
  • x-axis label:
plt.xlabel("PRVI (dB)")
  • y-axis label:
plt.ylabel("NDVI")
  • erase labels:
plt.tick_params(labelbottom=False, labelleft=False, labelright=False, labeltop=False)

Color

help(matplotlib.cm)
  • Change color table of a map:
plt.imshow(x, cmap=matplotlib.cm.gray) # このgrayのところをカラーテーブル名にする。
  • Reverse the color map: Put "_r" at the end of the color map name.
plt.imshow(x, cmap=matplotlib.cm.rainbow_r)

output

  • create a png file:
plt.savefig(title+'_LC.png', bbox_inches="tight")
# ("bbox_inches="tight" is good for removing big empty space surrounding the picture)
Last modified:2020/03/23 12:13:02
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