使用略图库调整图像大小而不拉伸

Question

嘿，我正在尝试调整图像的大小，而不是拉伸它，而是添加白色像素。我看起来很傲慢，但我没有发现任何东西能说明如何在撇油的情况下做到这一点。所以我使用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 我们可以看到列已经被添加，但是在我用

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

这些图像看起来像负片，调整大小后的图像看起来完全是白色的（在站点背景上看不见的黑色旁边）。有什么想法吗？

Answer 1

下面的代码应该可以工作。请注意，为了查看上载图像中的图像边界，填充区域的颜色并非完全为白色。对于白色填充集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)