Python嵌套while循环不会按预期增加

Question

我正在Python中编写一个函数来使图像像素化，但由于某些原因，xx和x不会增加。两个变量始终保持值0，并没有任何反应。

xx = 0 
yy = 0 

while xx < width: 
    while yy < height: 
     print ("---", xx, yy) 
     offsetX = xx + block_size_half 
     offsetY = yy + block_size_half 

     while (xx + offsetX >= width): 
      offsetX -= 1 
     while (yy + offsetY >= height): 
      offsetY -= 1 

     r, g, b = matrix[xx + offsetX][yy + offsetY] 

     x = xx 
     y = yy 
     while x < xx + block_size and x < width: 
      while y < yy + block_size and y < height: 
       print (x, y) 
       matrix[x][y] = (r, g, b) 
       y += 1 

      x += 1 

     yy += block_size 

    xx += block_size 

感谢@Elazar的帮助！这里是整个工作的功能：

def pixelate(matrix, block_size): 
    width = len(matrix) 
    height = len(matrix[0]) 
    block_size_half = int(block_size/2) 

    for xx in range(0, width, block_size): 
     for yy in range(0, height, block_size): 

      offsetX = min(xx + block_size_half, width - 1) 
      offsetY = min(yy + block_size_half, height - 1) 

      r, g, b = matrix[offsetX][offsetY] 

      for x in range(xx, min(xx + block_size, width)): 
       for y in range(yy, min(yy + block_size, height)): 
        matrix[x][y] = (r, g, b) 

我的灵感来自这个C＃实现的算法： http://notes.ericwillis.com/2009/11/pixelate-an-image-with-csharp/

Answer 1

我可以看到你为什么不使用xrange()（或range()）没有理由

for xx in range(0, width, block_size): 
    for yy in range(0, height, block_size): 
     ... 

[编辑]

重写整个例子，你会得到一些东西如：

for xx in range(0, width, block_size): 
    for yy in range(0, height, block_size): 
     print ("---", xx, yy) 
     offsetX = min(width, xx + block_size_half) 
     offsetY = min(height, yy + block_size_half) 

     r, g, b = matrix[xx + offsetX][yy + offsetY] 

     for x in range(xx, min(xx + block_size, width)): 
      for y in range(yy, min(yy + block_size, height)): 
       print (x, y) 
       matrix[x][y] = (r, g, b) 

它可能会变得更短。