为什么提取深度数据的代码需要把y写前面x写后面 depth_frame[y, x] 或者get_distance(j, i)

ChatGPT的回答：

The code line distance = depth_frame[y_coordinate, x_coordinate] suggests that depth_frame is accessed using row-major order, which is typical in many programming languages and libraries dealing with matrices or two-dimensional arrays. In this context, the first index (y_coordinate) selects the row, and the second index (x_coordinate) selects the column within that row. This ordering convention is rooted in the way matrices are conventionally represented in mathematics, where a position within a matrix is often denoted as (row, column) or (i, j), with i indicating the row and j the column.

This approach also aligns with the Cartesian coordinate system used in images, where the origin (0, 0) is typically at the top-left corner. The y-coordinate then indicates how far down from the top the pixel is (the row in the image data), and the x-coordinate indicates how far to the right from the left edge the pixel is (the column in the image data).

In many programming languages and libraries that process images or matrices (such as NumPy in Python, MATLAB, and OpenCV), this convention is used because it reflects the underlying data structure of an image or a matrix as a series of rows, where each row is a series of elements. Thus, accessing an element through [row, column] or [y, x] is both intuitive in terms of mathematical notation and efficient for accessing contiguous memory locations in row-major storage systems.

画个图示意一下：

简言之，图片的深度值存在一个矩阵中，按照像素坐标调取矩阵中相应位置的元素。

举例：
假如你想要获得深度值的这个像素在像素坐标中的表示为 (x0, y0) = (500, 300)，那么这个像素点对应的深度值，可以按照去深度矩阵中的第300行(row)，第500列(column)去找。如果像素矩阵的名称表示为depth_frame，那么该像素的深度值即为depth_frame[300, 500]