使用 skimage 库调整图像大小而不拉伸

Question

嘿，我正在尝试调整图像大小而不拉伸它，而是添加白色像素。我环顾四周，但没有发现任何具体说明如何从 skimage 中实现这一点。因此，我使用 numpy 在调整大小之前添加额外的像素作为 [float(255)] 数组。

from skimage.io import imread
from skimage.io import imsave
from skimage.transform import resize
from matplotlib import pyplot as plt
from pylab import cm
import numpy as np
from skimage import morphology
from skimage import measure
from scipy import misc
def process(file_):
    im = imread(file_, as_grey=True)
    #im = misc.imread(file_)
    #im=np.fromfile(file_, dtype=np.int64)

    #Filler to avoid stretching
    orig_rows, orig_cols = im.shape
    print orig_rows, orig_cols
    if orig_rows < orig_cols:
        for addition in range(0,orig_cols-orig_rows):
            #adding white rows
            lst = np.array(list(float(255) for x in range(0,orig_cols)))
            im= np.vstack((im,lst))
    if orig_rows > orig_cols:
        for addition in range(0,orig_rows-orig_cols):
            #adding white columns
            lst = np.array(list([float(255)] for x in range(0,orig_rows)))
            im= np.hstack((im,lst))
    image = resize(im, (48, 48))
    imsave('test.jpg',im)
    imsave('test1.jpg',image)
    plt.imshow(im, cmap=cm.gray)
    plt.show()

当我用 pyplot 查看图像时，它看起来像这样 我们可以看到列已添加，但是在我保存图像后

image = resize(im, (48, 48))
    imsave('test.jpg',im)
    imsave('test1.jpg',image)

图像看起来像底片，调整大小后的图像看起来完全是白色的（在黑暗旁边，它在网站背景上不可见）。有任何想法吗？

Answer 1

下面的代码应该可以工作。请注意，填充区域的颜色并不完全是白色，以便在上传的图像中看到图像边界。适用于白色衬垫套装fill_cval = np.max(img)。

def resize_padded(img, new_shape, fill_cval=None, order=1):
    import numpy as np
    from skimage.transform import resize
    if fill_cval is None:
        fill_cval = np.max(img)
    ratio = np.min([n / i for n, i in zip(new_shape, img.shape)])
    interm_shape = np.rint([s * ratio for s in img.shape]).astype(np.int)
    interm_img = resize(img, interm_shape, order=order, cval=fill_cval)

    new_img = np.empty(new_shape, dtype=interm_img.dtype)
    new_img.fill(fill_cval)

    pad = [(n - s) >> 1 for n, s in zip(new_shape, interm_shape)]
    new_img[[slice(p, -p, None) if 0 != p else slice(None, None, None) 
             for p in pad]] = interm_img

    return new_img

import numpy as np
import matplotlib.pylab as plt
from skimage.data import astronaut
from skimage.color import rgb2gray  # using luminance
from skimage.io import imsave
img = rgb2gray(astronaut())

# set desired image size
out_size = (30, 100)  # height, width

# set the color of the padded area. Here: "95% luminance"
fill_cval = np.max(img) * 0.95

resized_img = resize_padded(img, out_size, fill_cval=fill_cval)

imsave('img.png', img)
imsave('img_res.png', resized_img)