你需要更好地利用numpy切片。据我所知，两个随机数组coords_r, coords_c是你想要放置星星的中心坐标。我会
1.将这些转换为矩形裁剪坐标列表
1.在坐标上循环并将星星放置在每个切片中
事

def center_to_bbox(coords, star_size):
    coords_x, coords_y = coords
    x1, y1, x2, y2 = coords_x - star_size, coords_y - star_size, coords_x + star_size + 1, 
    coords_y + star_size + 1,
    bboxes =(x1, y1, x2, y2)
    return bboxes
x_coords = np.random.randint(0, 250 - 3, 20)  
y_coords = np.random.randint(0, 250 - 3 , 20)
x1, y1, x2, y2 = bboxes
for x1_, y1_, x2_, y2_ in zip(x1, y1, x2, y2):
    matrix[y1_:y2_, x1_:x2_] = star

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还请注意，您也可以减去星星的维度，这样就不必在以后的边界处进行补偿

看起来你可能想使用scipy sparse matrices。只需定义小矩阵并将它们添加到更大的矩阵中。lil_matrix似乎是你正在寻找的合适格式。
编辑：@iantonuk我在想下面的方法，它在添加/组装矩阵时效果很好，但在替换条目时效果不好。

from scipy.sparse import coo_matrix
data1 = ((1.0,2.0,3.0),([0,1,2],[0,1,2]))
mat1  = coo_matrix(data1,shape=(3,3))
print(mat1.todense())
data2 = ((2.0,3.0),([1,2],[1,2]))
mat2  = coo_matrix(data2,shape=(3,3))
print(mat2.todense())
mat3  = mat1 + mat2
print(mat3.todense())

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我问过类似的问题：Add small image to the canvas as numpy arrays
以下是我对你的问题的解决方案：

matrix_size = 250
star_size = 3

matrix = np.ones((matrix_size, matrix_size))
star = 1 - skimage.morphology.diamond(star_size)

coords_r = np.random.randint(0, matrix_size, 20)  # row coordinates
coords_c = np.random.randint(0, matrix_size, 20)  # column coordinates

for r, c in zip(coords_r, coords_c):
    matrix[max(r - star_size, 0):r + star_size + 1, max(c - star_size, 0):c + star_size + 1] *= star[max(star_size - r, 0):star_size + matrix_size - r, max(star_size - c, 0):star_size + matrix_size - c]
matrix = 1-matrix

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这就是我得到的：

以下是你可以用矢量化的方式轻松做到这一点：

def put_rounds(image:np.array, ptsx, ptsy):
    xm1, x, xp1 = (ptsx-1,ptsx,ptsx+1)
    ym1, y, yp1 = (ptsy-1,ptsy,ptsy+1)

    #make a round, r=3 or diamond pattern or whatever you need
    ptsx3 = np.dstack((xm1, xm1, ptsx,xm1,ptsx, xp1, ptsx,xm1, xp1)).flatten()
    ptsy3 = np.dstack((ym1, yp1, ym1,ptsy,ptsy, ptsy,yp1, yp1, yp1)).flatten()

    #this at least 7.5-12 times faster then loops(at least 50+ times faster on torch)
    image[ptsy3, ptsx3] = np.array([255,255,0])

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