Leetcode_Python 661 图片平滑器

# 661
class Solution(object):
    def imageSmoother(self, M):
        """
        :type M: List[List[int]]
        :rtype: List[List[int]]
        """
        #定义图片的高与宽
        length_h,length_w = len(M),len(M[0])
        #在给定图片的外围添加"_"
        '''
        [['_', '_', '_', '_', '_'],
         ['_',  1,   1,   1,  '_'],
         ['_',  1,   0,   1,  '_'],
         ['_',  1,   1,   1,  '_'],
         ['_', '_', '_', '_', '_']]
        '''    
        mask = []
        for i in range(length_h + 2):
            if i in [0,length_h+1]:
                mask.append(["_"]*(length_w+2))
            else:
                mask.append(["_"]+M[i - 1]+["_"])
        #类似卷积定理通过滑窗求平均值
        column = []
        for i in range(length_h):
            row = []
            for j in range(length_w):
                count,sum = 0,0  #count为计数，sum求子窗的和
                cell = [mask[i][j],  mask[i][j+1],  mask[i][j+2],
                        mask[i+1][j],mask[i+1][j+1],mask[i+1][j+2],
                        mask[i+2][j],mask[i+2][j+1],mask[i+2][j+2]]  #求出子窗的数列
                for num in cell:  #统计子窗平均值
                    if num in range(0,256):
                        count += 1
                        sum += num
                mean = sum//count
                row.append(mean)
            column.append(row)
        return column