如何在python中调整输出图像的大小？

Question

嗨，我用python运行这个模糊检测代码(来源：https://www.pyimagesearch.com/2015/09/07/blur-detection-with-opencv/ )

# import the necessary packages
from imutils import paths
import argparse
import cv2

def variance_of_laplacian(image):
    # compute the Laplacian of the image and then return the focus
    # measure, which is simply the variance of the Laplacian
    return cv2.Laplacian(image, cv2.CV_64F).var()

# loop over the input images
for imagePath in paths.list_images("images/"):
    # load the image, convert it to grayscale, and compute the
    # focus measure of the image using the Variance of Laplacian
    # method
    image = cv2.imread(imagePath)
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    fm = variance_of_laplacian(gray)
    text = "Not Blurry"

    # if the focus measure is less than the supplied threshold,
    # then the image should be considered "blurry"
    if fm < 100:
        text = "Blurry"

        # show the image
    cv2.putText(image, "{}: {:.2f}".format(text, fm), (10, 30),
    cv2.FONT_HERSHEY_SIMPLEX, 0.8, (0, 0, 255), 3)
    cv2.imshow("Image", image)
    print("{}: {:.2f}".format(text, fm))
    key = cv2.waitKey(0)

使用此2173x3161输入文件input image

这是输出，the output image，图像是放大的，没有完整显示。

在源代码中，它们使用450x600px输入图像：input in source code，输出是：output in source code

我认为图像的像素会影响输出。那么，我如何才能得到像源代码中的输出一样的输出到所有图像呢？我必须调整输入图像的大小吗？怎么做？但如果我这样做，恐怕会影响他模糊的结果

Answer 1

摘自DOCUMENTATION。

有一种特殊的情况，在这种情况下，您可以创建一个窗口，然后将图像加载到其中。在这种情况下，您可以指定窗口是否可调整大小。这是通过cv2.namedWindow()函数完成的。缺省情况下，该标志为cv2.WINDOW_AUTOSIZE.但是，如果将标志指定为cv2.WINDOW_NORMAL，，则可以调整窗口大小。当图像尺寸太大，并向窗口添加跟踪条时，这将是很有帮助的。

我只使用了问题中的代码，但添加了注释中提到的cv2.namedWindow("Image", cv2.WINDOW_NORMAL)行。

# import the necessary packages
from imutils import paths
import argparse
import cv2

def variance_of_laplacian(image):
    # compute the Laplacian of the image and then return the focus
    # measure, which is simply the variance of the Laplacian
    return cv2.Laplacian(image, cv2.CV_64F).var()

# loop over the input images
for imagePath in paths.list_images("images/"):
    # load the image, convert it to grayscale, and compute the
    # focus measure of the image using the Variance of Laplacian
    # method
    image = cv2.imread(imagePath)
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    fm = variance_of_laplacian(gray)
    text = "Not Blurry"

    # if the focus measure is less than the supplied threshold,
    # then the image should be considered "blurry"
    if fm < 100:
        text = "Blurry"

        # show the image
    cv2.putText(image, "{}: {:.2f}".format(text, fm), (10, 30),
    cv2.FONT_HERSHEY_SIMPLEX, 0.8, (0, 0, 255), 3)
    cv2.namedWindow("Image", cv2.WINDOW_NORMAL)       #---- Added THIS line
    cv2.imshow("Image", image)
    print("{}: {:.2f}".format(text, fm))
    key = cv2.waitKey(0)

Answer 2

如果希望使用与所给示例完全相同的分辨率，则可以只使用cv2.resize() https://docs.opencv.org/2.4/modules/imgproc/doc/geometric_transformations.html#resize方法，或者(如果希望保持x/y坐标的比率)使用https://www.pyimagesearch.com/2015/02/02/just-open-sourced-personal-imutils-package-series-opencv-convenience-functions/中提供的imutils类

您仍然需要决定是否要先调整大小。灰度化或调整大小的顺序应该无关紧要。

可以添加的命令：resized_image = cv2.resize(image, (450, 600))