python numpy 图片 pad 参数详解

python numpy 图片 pad 参数详解

'constant', 'edge', 'linear_ramp', 'maximum', 'mean', 'median', 'minimum', 'reflect', 'symmetric', 'wrap', 'empty'  

光看文档不太好理解，因为在网上找不到详细的例子，所以我就自己动手做了一个例子。  

为了更好的演示，我剪裁了原图右边和下边的留白区域。  

```  

mode : str or function, optional

    One of the following string values or a user supplied function.

    'constant' (default)

        Pads with a constant value.

    'edge'

        Pads with the edge values of array.

    'linear_ramp'

        Pads with the linear ramp between end_value and the array edge value.

    'maximum'

        Pads with the maximum value of all or part of the vector along each axis.

    'mean'

        Pads with the mean value of all or part of the vector along each axis.

    'median'

        Pads with the median value of all or part of the vector along each axis.

    'minimum'

        Pads with the minimum value of all or part of the vector along each axis.

    'reflect'

        Pads with the reflection of the vector mirrored on the first and last values of the vector along each axis.

    'symmetric'

        Pads with the reflection of the vector mirrored along the edge of the array.

    'wrap'

        Pads with the wrap of the vector along the axis. The first values are used to pad the end and the end values are used to pad the beginning.

    'empty'

        Pads with undefined values.

```  

modes = ['constant', 'edge', 'linear_ramp', 'maximum', 'mean', 'median', 'minimum', 'reflect', 'symmetric', 'wrap', 'empty' ]
pic = cv2.imread('D:/share/QRcode/taobao.jpg') 
pic = cv2.cvtColor(pic, cv2.COLOR_BGR2RGB)
plt.figure(figsize=(500,120))
plt.subplot(12,1,1)
plt.title('Raw(Cut right and down side)')
plt.imshow(pic)
for index, mode in enumerate(modes):
    plt.subplot(12,1,index+2)
    pic_pad = np.pad(pic, ((100,100), (100,100), (0,0)) , mode)
    plt.title(mode)
    plt.imshow(pic_pad)