[PYTHON] I want to display an image on Jupyter Notebook using OpenCV (mac)

Image analysis for python beginners

Record what you failed and what you could improve from a beginner's point of view.

This time, on the Jupyter Notebook launched from Anaconda Contents that caused an error when displaying an image using OpenCV. (The image below is a successful example)

Also, when the image quality was displayed, the resolution had dropped, so I'm looking for ways to improve it. (If anyone knows, please teach me ...)

conditions

・ Using macOS ・ I want to display it on Jupyter Notebook on Anaconda -Use Python 3.7 -Use OpenCV 4.1.1 -Use matplotlib -Images (shimarisu.jpg) are stored in a folder on the desktop of mac. 　/Desktop/detect_ai/data/shimarisu.jpg

OpenCV installation

Since only OpenCV was not installed in Anaconda https://rightcode.co.jp/blog/information-technology/opencv-jupyternotebook-face-recognition I tried it with reference to, but for some reason I couldn't. You can select OpenCV and press the Apply button to start the installation I cannot press the Apply button after the installation is complete.

So, enter `$ pip install opencv-python` in the terminal and execute. In yellow letters, it is displayed as WARNING, Since it is "Successfully installed opencv-python-4.1.1.26" The installation seems to be successful.

Display images using OpenCV

Display the image on Jupyter Notebook. This time, the image of chipmunk.

Source code

I referred to this. https://teratail.com/questions/169009

opencv.ipynb

import matplotlib.pyplot as plt
import numpy as np
import cv2

#Inline display
%matplotlib inline

#image(shimarisu.jpg)Loading
img = cv2.imread("shimarisu.jpg ")

#Image display
plt.imshow(cv2.cvtColor(img, cv2.COLOR_BGR2RGB)) #OpenCV colors are in GBR order, so sort them in RGB order
plt.show()

However, I got the following error.

opencv.ipynb

error                                     Traceback (most recent call last)
<ipython-input-33-7c8a2c33eec7> in <module>
     10 
     11 #Image display
---> 12 plt.imshow(cv2.cvtColor(img, cv2.COLOR_BGR2RGB)) #OpenCV colors are in GBR order, so sort them in RGB order
     13 plt.show()

error: OpenCV(4.1.1) /Users/travis/build/skvark/opencv-python/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'

◆ After investigating the cause, the location of the python file that is currently up (on Anaconda) and The location (on Desktop) of the image (shimarisu.jpg) you want to display is different. https://ja.stackoverflow.com/questions/49260/python3-6-6%E3%81%AB%E3%81%A6cv2%E3%82%A8%E3%83%A9%E3%83%BC%E3%81%8C%E7%99%BA%E7%94%9F%E3%81%97%E3%81%BE%E3%81%99

The image I wanted to display (shimarisu.jpg) was stored in a folder on the desktop of the mac. /Desktop/detect_ai/data/shimarisu.jpg

What I tried

In the 5th line of the 1st image, the reading part of the image (shimarisu.jpg)

img = cv2.imread ("shimarisu.jpg ") img = cv2.imread("/Users/name/Desktop/detect_ai/data/shimarisu.jpg ")

After replacing it with, the image was displayed!

Points to note

It is necessary to align the location of the python file that is up and the hierarchy of the storage location of the image. It is necessary to describe "The image (shimarisu.jpg) is stored in the folder on the desktop of mac". In this case /Users/(name displayed in the terminal) /Desktop/detect_ai/data/shimarisu.jpg

(The name displayed in the terminal) varies from person to person. The image below is just described as "name" as an example, so please change it at any time.

problem

However, the resolution of the image quality will be reduced and displayed, so keep the resolution of the original image. We are currently verifying whether the image can be displayed. (I will update if there is progress)

Other reference sites

-Source code for displaying images with OpenCV http://peaceandhilightandpython.hatenablog.com/entry/2015/12/23/214840 http://rasp.hateblo.jp/entry/2016/01/22/201534