Save JPEG With Specific Quality | OpenCV vs Pillow | Python
This tutorial will show you how to write/save images in jpg format and specify the image quality in both OpenCV (cv2) and Pillow (PIL).
Specify JPEG Quality
The recommended range for image quality is from 1 (worst) to 95 (best). Values above 95 should be avoided since 100 will disable portions of the JPEG compression algorithm, and result in large files without better image quality.
# Pillow
pil_img.save("new_image.jpg", quality=95)
# OpenCV
cv2.imwrite("new_image.jpg", cv2_img, [cv2.IMWRITE_JPEG_QUALITY, 95])If the JPEG quality is not specified, they will save the image in the following default quality:
| Pillow (PIL) | OpenCV (cv2) | |
|---|---|---|
| Default JPEG Quality | 75 | 95 |
Full Example
You might also want to learn how to read images using cv2 and PIL.
Pillow
from PIL import Image
# read images
pil_img = Image.open("test_images/test1.jpg")
# write jpeg with quality=50
pil_img.save("test_images/pil_compressed_image.jpg", quality=50)OpenCV
import cv2
# read images
cv2_img = cv2.imread("test_images/test1.jpg")
# write jpeg with quality=50
cv2.imwrite("test_images/cv2_compressed_image.jpg", cv2_img, [cv2.IMWRITE_JPEG_QUALITY, 50])Syntax
Pillow
Image.save(fp, format=None, **params)Parameters:
fp: A filename (string),pathlib.Pathobject or file object.format: Optional format override. If omitted, the format to use is determined from the filename extension. This parameter should always be used if a file object is used instead of a filename.params: Extra parameters to the image writer. See the documentation for available options for each writer.
Returns:
None
OpenCV
cv2.imwrite(filename, img[, params])Parameters:
filename: Name of the file.img: Image or Images to be saved (Numpy array).params: Format-specific parameters encoded as pairs (paramId_1, paramValue_1, paramId_2, paramValue_2, … .) see cv::ImwriteFlags.
Returns:
Trueif succeeded, OtherwiseFalse.
