OpenCV image quality

• Start Docker

After entering the Raspberry Pi 5 desktop, open a terminal and run the following command to start the container corresponding to Dofbot:

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./Docker_Ros.sh

Access Jupyter Lab within Docker:

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IP:9999 // Example: 192.168.1.11:9999

Code path:/root/Dofbot/4.opencv/1.OpenCV_basic/03_quality_pic.ipynb

1. Compression method.

cv2.imwrite('yahboomTest.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, 50])

cv2.CV_IMWRITE_JPEG_QUALITY: Set the image quality of the image format to .jpeg or .jpg, the value is 0---100 (the larger the value, the higher the quality), the default is 95

cv2.CV_IMWRITE_WEBP_QUALITY: Set the image format to .webp format image quality, the value is 0--100

cv2.CV_IMWRITE_PNG_COMPRESSION: Set the compression ratio of .png format, the value is 0--9 (the larger the value, the greater the compression ratio), the default is 3

The main code is as follows:

import cv2
img = cv2.imread('yahboom.jpg',1)
cv2.imwrite('yahboomTest.jpg', img, [cv2.IMWRITE_JPEG_QUALITY, 50])
#1M 100k 10k 0-100 Lossy compression

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# 1 lossless 2 transparency attribute
import cv2
img = cv2.imread('yahboom.jpg',1)
cv2.imwrite('yahboomTest.png', img, [cv2.IMWRITE_PNG_COMPRESSION,0])
# jpg 0 compression ratio higher 0-100 png 0 compression ratio lower 0-9

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#bgr8 to jpeg format
import enum
import cv2
def bgr8_to_jpeg(value, quality=75):
       return bytes(cv2.imencode('.jpg', value)[1])

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import ipywidgets.widgets as widgets
image_widget1 = widgets.Image(format='jpg', )
image_widget2 = widgets.Image(format='jpg', )
# create a horizontal box container to place the image widget next to each other
image_container = widgets.HBox([image_widget1, image_widget2])
# display the container in this cell's output
display(image_container)
img1 = cv2.imread('yahboomTest.jpg',1)
img2 = cv2.imread('yahboomTest.png',1)
image_widget1.value = bgr8_to_jpeg(img1)
image_widget2.value = bgr8_to_jpeg(img2)

When the code block runs to the end, you can see the comparison of the two photos.