python - OpenCV .imshow() 未显示正确大小的图像

Question

我正在尝试使用 opencv 读取图像，进行一些转换(调整大小和偏移)，然后作为最后一步，对图像进行裁剪。在我的最后一行 crop_img = offset_image[0:1080, 0:1920].copy() 中，我希望创建一个裁剪后的 1920x1080 图像。我的 crop_img.size 打印输出表明这是正确的。但是，当我执行 .imshow() 时，它会显示完整尺寸的原始图像。

import numpy as np
import cv2 as cv
import copy

original = cv.imread("IMG_0015_guides.jpg", cv.IMREAD_UNCHANGED)
img_resize = cv.resize(original, (0,0), fx=.9, fy=.9) 


rows,cols,_ = img_resize.shape
M = np.float32([[1,0,100],[0,1,50]])
offset_image = cv.warpAffine(img_resize,M,(cols,rows))

crop_img = offset_image[0:1080, 0:1920].copy()

print('img_resize {}'.format(img_resize.shape))
print('offset_image {}'.format(offset_image.shape))
print('cropped {}'.format(crop_img.shape))

cv.imshow('image',crop_img)
cv.waitKey(0)
cv.destroyAllWindows()

>>> img_resize (3110, 4666, 3)
>>> offset_image (3110, 4666, 3)
>>> cropped (1080, 1920, 3)

我完全不知所措。为什么它不显示裁剪后的 1920x1080 图片？

Answer 1

在使用 OpenCV 的 imshow 进行可视化时，处理大量图像可能会让人感到困惑。 我运行了你的代码，它似乎在做你期望它做的事情。我建议仅出于可视化目的再次调整图像大小。以下代码在此 image 上成功运行.

import numpy as np
import cv2 as cv
import copy

original = cv.imread("4k-image-tiger-jumping.jpg", cv.IMREAD_UNCHANGED)

# resize original for visualization purposes only
print('original {}'.format(original.shape))
original_resized = cv.resize(original, (0,0), fx=.1, fy=.1) 
cv.imshow('original_resize',original_resized)


img_resize = cv.resize(original, (0,0), fx=.9, fy=.9) 

rows,cols,_ = img_resize.shape
M = np.float32([[1,0,100],[0,1,50]])
offset_image = cv.warpAffine(img_resize,M,(cols,rows))

crop_img = offset_image[0:1080, 0:1920].copy()

print('img_resize {}'.format(img_resize.shape))
print('offset_image {}'.format(offset_image.shape))
print('cropped {}'.format(crop_img.shape))


# resize cropped for visualization purposes only
vis_r,vis_c,_ = original_resized.shape
cropped_resized = cv.resize(crop_img, (vis_c, vis_r))
cv.imshow('cropped_resized',cropped_resized)


# cv.imshow('image',crop_img)

cv.waitKey(0)
cv.destroyAllWindows()