切片numpy数组的不同部分

Question

我正在导入图像并将它们转换为 numpy 数组。我想分析它们，但它们对于我程序的下一步来说太大了。输入图像为 640 x 480，我正在分析 400x400。我想裁剪这些图像的部分而不是调整大小，这样我就不会丢失任何细节。我想在整个图像上创建分析大小为 400x400 的“蒙版”。 例如，这张图片中应该有 4 个蒙版

0:400,0:400
0:400,80:480
240:640,0:400
240:640:80:480

我当前的代码是这样的： frame 是图像的 numpy 数组

frmwidth = frame.shape[0]
frmheight = frame.shape[1]
# print(frmwidth)
# print(frmheight)
res_width, res_height = 400,400

number_width = math.ceil(frmwidth/res_width)
number_height = math.ceil(frmheight/res_height)
iter = max(number_width, number_height)
print(number_width)
print(number_height)


print('\n\nBOUNDS')
topbound = 0
for i in range(number_width):
    leftbound = 0

    for j in range(number_height):
        if leftbound == 0 and topbound == 0:
            rightbound = leftbound + 400
            print('width')
            print(leftbound)
            print(rightbound)
            leftbound = rightbound

            bottombound = topbound+400
            print('heigth')
            print(topbound)
            print(bottombound)
            topbound = bottombound

        elif leftbound == 0 and topbound != 0:
            rightbound = leftbound + 400
            print('width')
            print(leftbound)
            print(rightbound)
            leftbound = rightbound

            topbound = topbound - ((res_height*number_height)-frmheight)/(number_height-1)
            bottombound = topbound+400
            print('height')
            print(topbound)
            print(bottombound)

        elif topbound == 0 and leftbound != 0:
            leftbound = leftbound - ((res_width*number_width)-frmwidth)/(number_width-1)
            rightbound = leftbound+400
            print('width')
            print(leftbound)
            print(rightbound)
            bottombound = topbound+400

            print('heigth')
            print(topbound)
            print(bottombound)
            topbound = bottombound
        else:
            leftbound = leftbound - ((res_width*number_width)-frmwidth)/(number_width-1)
            rightbound = leftbound+400
            print('width')
            print(leftbound)
            print(rightbound)

            topbound = topbound - ((res_height*number_height)-frmheight)/(number_height-1)
            bottombound = topbound+400
            print('height')
            print(topbound)
            print(bottombound)

我已将 leftbound=0 和 rightbound=0 移入和移出 for 循环。这是我得到的最接近 3/4 的“面具”正确。

BOUNDS
width
0
400
heigth
0
400
width
80.0
480.0
height
240.0
640.0
width
0
400
height
80.0
480.0
width
80.0
480.0
height
-80.0
320.0

我为所有的印刷声明道歉，它让一切井井有条

这部分(res_width*number_width)-frmwidth)/(number_width-1) 计算每个作物与前一个作物的重叠程度。

Answer 1

这不能回答您的问题吗？ （如果尺寸和切口始终相同）：

sub_img1 = frame[0:400,0:400]
sub_img2 = frame[0:400,80:480]
sub_img3 = frame[240:640,0:400]
sub_img4 = frame[240:640:80:480]

有时简单的硬编码比概括情况更容易。

编辑：对于一般情况，此代码为您提供图像窗口数组：

from skimage.util.shape import view_as_windows
window_shape = (400,400)
step = 400
B1 = view_as_windows(frame, window_shape, step)
B2 = view_as_windows(frame[-window_shape[0]:,:], window_shape, step)
B3 = view_as_windows(frame[:,-window_shape[1]:], window_shape, step)
B4 = view_as_windows(frame[-window_shape[0]:,-window_shape[1]:], window_shape, step)
arr_sub_images = np.vstack((B1.reshape(-1,*window_shape),B2.reshape(-1,*window_shape),B3.reshape(-1,*window_shape),B4.reshape(-1,*window_shape)))

Answer 2

我想出了一个使用np.linspace 的解决方案。 linspace 找到每个裁剪的中心点，然后我针对 x 和 y 轴中的每一个遍历 linspace 并将它们用作组合来获取位置。然后我们加或减 200（在本例中为 400x400 裁剪）得到裁剪。

frmwidth = frame.shape[0]
frmheight = frame.shape[1]
print(frame.shape)
res_width, res_height = 400,400

number_width = math.ceil(frmwidth/res_width)
number_height = math.ceil(frmheight/res_height)
iter = max(number_width, number_height)

y_centers = np.linspace((res_height/2), (frmheight-(res_height/2)), math.ceil(frmheight/res_height))
x_centers = np.linspace((res_width/2), (frmwidth-(res_width/2)), math.ceil(frmwidth/res_width))
for i in y_centers:
    for j in x_centers:
        i = int(i)
        j = int(j)
        topbound = i-200
        bottombound = i+200
        leftbound = j-200
        rightbound = j+200
        frame = frame[i-200:i+200,j-200:j+200]