1.np.where 返回滿足條件的位置
aa[np.where(array1>doubleThreshold)]=1
2.圖像處理中，灰度圖顯示并不是按實(shí)際的灰度值進(jìn)行顯示：
a=np.zeros([512,512]) for i in range(512): for j in range(512): a[i,j]=255
灰度值的范圍為0-255:0：黑色 255:白色。
現(xiàn)在本來應(yīng)該全顯示為白色，卻都顯示為黑色，下面一探究竟。
PIL官方文檔PIL
pyplot的顯示有自己的配色方案，所以可能顯示并不是灰度值，正確的做法如下
a=np.zeros([512,512]) I=Image.fromarray(a).convert('L') I.save('test.png')
3.Mode #
The mode of an image defines the type and depth of a pixel in the image. The current release supports the following standard modes:
1 (1-bit pixels, black and white, stored with one pixel per byte)
L (8-bit pixels, black and white)
P (8-bit pixels, mapped to any other mode using a colour palette)
RGB (3x8-bit pixels, true colour)
RGBA (4x8-bit pixels, true colour with transparency mask)
CMYK (4x8-bit pixels, colour separation)
YCbCr (3x8-bit pixels, colour video format)
I (32-bit signed integer pixels)
F (32-bit floating point pixels)
3.pickle
寫入文件
f1 = file('temp.pkl', 'wb') pickle.dump(a1, f1, True)
讀pickle文件
import cPickle as pickle f2 = file('dcmdata.pkl', 'rb') dcmdata=pickle.load(f2)
numpy.nonzero 返回坐標(biāo)
x = np.array([[1,0,0], [0,2,0], [1,1,0]]) x
array([[1, 0, 0], [0, 2, 0], [1, 1, 0]])
np.nonzero(x)
`
(array([0, 1, 2, 2], dtype=int64), array([0, 1, 0, 1], dtype=int64))
`
numpy.count_nonzero 返回個數(shù)
np.count_nonzero(np.eye(4))
4
np.count_nonzero([[0,1,7,0,0],[3,0,0,2,19]])
5
np.count_nonzero([[0,1,7,0,0],[3,0,0,2,19]], axis=0)
array([1, 1, 1, 1, 1])
np.count_nonzero([[0,1,7,0,0],[3,0,0,2,19]], axis=1)
array([2, 3])
可用來判斷符合某一條件的個數(shù)：
np.count_nonzero(examplearray==5)
5.安裝keras,使用
`
pip install keras
`
6.pickle在python2與python3之間的兼容性問題：
直接load會出現(xiàn)
``
UnicodeDecodeError: 'ascii' codec can't decode byte 0xca in position 0: ordinal not in range(128)
``
的問題。
解決方法：
airway=pickle.load(f2,encoding='latin1')
