图片由opencv加载错误

Question

灾难！

如您所见，图像未正确加载。原本的：

代码：

import cv2
import imutils
a=imutils.url_to_image("https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_272x92dp.png", readFlag=-1)
cv2.imshow("goog", a)
cv2.waitKey()

在imutils中实现url_to_image：

def url_to_image(url, readFlag=cv2.IMREAD_COLOR):
    # download the image, convert it to a NumPy array, and then read
    # it into OpenCV format
    resp = urlopen(url)
    image = np.asarray(bytearray(resp.read()), dtype="uint8")
    image = cv2.imdecode(image, readFlag)

    # return the image
    return image

我还尝试了readFlag = cv2.IMREAD_UNCHANGED，但这也没有解决问题。

请发送帮助

Answer 1

好帮派，我们做到了

所以我尝试了另一种显示方式：

plt.figure("Correct")
plt.imshow(imutils.opencv2matplotlib(a))
plt.show()

不会出现运气。但是，然后查看opencv2matplotlib源，我们发现：

def opencv2matplotlib(image):
    # OpenCV represents images in BGR order; however, Matplotlib
    # expects the image in RGB order, so simply convert from BGR
    # to RGB and return
    return cv2.cvtColor(image, cv2.COLOR_BGR2RGB)

啊哈，但是我们有4个通道的颜色（alpha），所以从常识上讲我们需要cv2.COLOR_BGRA2RGBA而不是cv2.COLOR_BGR2RGB !!

检验这一理论：

plt.figure("Correct")
plt.imshow(cv2.cvtColor(a, cv2.COLOR_BGRA2RGBA))
plt.show()

我们得到...

呜呼嘘声！

Answer 2

# import the necessary packages
import numpy as np
import urllib
import cv2

def url_to_image(url):
    # download the image, convert it to a NumPy array, and then read
    # it into OpenCV format
    resp = urllib.request.urlopen(url)
    image = np.asarray(bytearray(resp.read()), dtype="uint8")
    image = cv2.imdecode(image, cv2.IMREAD_COLOR)

    # return the image
    return image


# initialize the list of image URLs to download
url="http://i.dailymail.co.uk/i/pix/2015/09/01/18/2BE1E88B00000578-3218613-image-m-5_1441127035222.jpg"

print ("downloading %s" % (url))
image = url_to_image(url)
cv2.imshow("Image", image)
cv2.waitKey(0)

输出为：