2-5 シンプルなコントラスト改善方法「コントラスト伸長」
img_src = cv2.imread("data/Mandrill.png")
#最小値
min = 70
#最大
max = 200
look_up_table = np.arange(256, dtype = np.uint8)
for i in range(0,255):
if i < min:
look_up_table[i] = 0
elif min <= i < max:
look_up_table[i] = 255 * (i - min)/(max - min)
else:
look_up_table[i] = 255
img_dst = cv2.LUT(img_src, look_up_table)
#描画する
cv2.imshow("img_src",img_src)
cv2.imshow("img_dst",img_dst)
cv2.waitKey(0)
cv2.destroyAllWindows()
#ヒストグラム
fig = plt.figure()
ax1 = fig.add_subplot(311) #総行数,総列数、サブプロット番号
ax2 = fig.add_subplot(312)
ax3 = fig.add_subplot(313)
color_list = ["blue","green","red"]
for i,j in enumerate(color_list):
hist = cv2.calcHist([img_src],[i],None,[256],[0,256])
ax1.plot(hist,color = j)
ax2.set_ylim(0,600)
for i,j in enumerate(color_list):
hist = cv2.calcHist([img_dst],[i],None,[256],[0,256])
ax2.plot(hist,color = j)
x = [x for x in range(256)]
ax3.plot(x,look_up_table)