如何將 canvas 的（行、列）position 的邊界框作為網格元組返回

Question

我正在嘗試編寫一個最終看起來像這樣的代碼：

畫布只是像素的海洋，所以我要做的就是添加一點額外的功能，讓導航更容易。 稍后我將在 canvas 上繪制矩形（好吧，正方形）來表示實體。

為此，我需要一個左上角和一個右下角像素坐標。 所以 get_bbox 允許從 Position(x,y) class 的實例（這是我們喜歡使用的，因為它存儲在我們的網格字典中）到這些像素坐標的轉換，使我們能夠輕松地使用 canvas 就像它的網格一樣.

class AbstractGrid(tk.Canvas):
    
    def __init__(self, master, rows, cols, width, height, **kwargs):
        """

        master: The window in which the grid should be drawn. 
        rows: The integer number of rows in the grid.
        cols: The integer number of columns in the grid.
        width: The width of the grid canvas (in pixels). 
        height: The height of the grid canvas (in pixels). 
        **kwargs: Any other additional named parameters appropriate to tk.Canvas.
        """
        master=self._master
        rows=self._rows
        cols=self._cols
        width=self._width
        height=self._height

        super().__init__(master, rows, cols, width, height, **kwargs)  
        
    def get_bbox(self, position):
        """
        Returns the bounding box for the (row, column) position;
        this is a tuple containing information about the pixel positions of the edges of the shape,
        in the form (x min, y min, x max, y max).

        """

我不知道如何寫這個get_bbox function。你能幫我一個辦法嗎？

謝謝

Answer 1

這是簡單的數學：

class AbstractGrid(tk.Canvas):

    def __init__(self, master, rows, cols, width, height, **kwargs):
        """

        master: The window in which the grid should be drawn.
        rows: The integer number of rows in the grid.
        cols: The integer number of columns in the grid.
        width: The width of the grid canvas (in pixels).
        height: The height of the grid canvas (in pixels).
        **kwargs: Any other additional named parameters appropriate to tk.Canvas.
        """
        super().__init__(master, width=width, height=height, **kwargs)

        self._rows = rows
        self._cols = cols
        self._width = width
        self._height = height
        # calculate the grid width and height
        self._grid_w = width / cols
        self._grid_h = height / rows

    def get_bbox(self, position):
        """
        Returns the bounding box for the (row, column) position;
        this is a tuple containing information about the pixel positions of the edges of the shape,
        in the form (x min, y min, x max, y max).

        """
        row, col = position
        x, y = col*self._grid_w, row*self._grid_h
        return x, y, x+self._grid_w, y+self._grid_h

請注意，我在__init__()內的以下幾行中修復了問題：

        master=self._master # self.master is created implicitly
        rows=self._rows     # should swap LHS and RHS on these four lines
        cols=self._cols
        width=self._width
        height=self._height

另請注意，如果您想要方形網格，最好指定單個網格大小而不是rows ， cols 。