Question

我有许多不同大小的图像，就像 images = [np.array(shape=(100, 200)), np.array(shape=(150, 100)), np.array(shape=200, 50)...]

是否有任何有效且便捷的方法将零填充到小图像（右下角填充零）并获得大小为（3，200，200）的numpy数组？

Answer 1

要向Numpy数组添加填充，可以使用以下命令：

中心填充：

shape = (200,200)
padded_images = [np.pad(a, np.subtract(shape, a.shape), 'constant', constant_values=0) for a in images]

右下角填充：

def pad(a):
    """Return bottom right padding."""
    zeros = np.zeros((200,200))
    zeros[:a.shape[0], :a.shape[1]] = a
    return zeros

vectorized_pad = np.vectorize(pad)
padded_images = vectorized_pad(images)

Answer 2

基于this solution，您可以执行以下操作在右侧和底部用零填充图像：

shape=(200,200)

new_images = [np.zeros(shape) for _ in range(len(images))]

for i,image in enumerate(images):
    new_images[i][:image.shape[0], :image.shape[1]] = image

示例：

举一个最小的例子，填充一组小图像以形成(5,5)的形状：

# Create random small images
images=[np.random.randn(2,3), np.random.randn(3,3), np.random.randn(5,5)]

# Print out the shape of each image just to demonstrate
>>> [image.shape for image in images]
[(2, 3), (3, 3), (5, 5)]
# Print out first image just to demonstrate
>>> images[0]
array([[-0.49739434,  1.06979644, -0.52647292],
       [ 1.21681931, -0.96205689,  0.050574  ]])

# Set your desired shape
shape=(5,5)

# Create array of zeros of your desired shape
new_images = [np.zeros(shape) for _ in range(len(images))]

# loop through and put in your original image values in the beginning
for i,image in enumerate(images):
    new_images[i][:image.shape[0], :image.shape[1]] = image

# print out new image shapes to demonstrate
>>> [image.shape for image in new_images]
[(5, 5), (5, 5), (5, 5)]
# print out first image of new_images to demonstrate:
>>> new_images[0]
array([[-0.49739434,  1.06979644, -0.52647292,  0.        ,  0.        ],
       [ 1.21681931, -0.96205689,  0.050574  ,  0.        ,  0.        ],
       [ 0.        ,  0.        ,  0.        ,  0.        ,  0.        ],
       [ 0.        ,  0.        ,  0.        ,  0.        ,  0.        ],
       [ 0.        ,  0.        ,  0.        ,  0.        ,  0.        ]])

填充图像的动态尺寸

2 个答案: