openCV set color is not displaying Red

Asked May 10 '17 at 16:38

Active May 10 '17 at 16:40

Viewed 136 times

Why when i set a specific color of a pixel does it not show solid red? And it also appears to affect the surrounding pixels and not just the specific pixel I chose.

code

import cv2
import numpy
import os
print cv2.__version__

width = 60
height = 40

# create simple RGB images
img = numpy.zeros((height,width,3), numpy.uint8)
img[30,20] = [0,0,255]

cv2.imwrite('RGB.jpg', img, [int(cv2.IMWRITE_JPEG_QUALITY), 100])
os.startfile('RGB.jpg')

edited May 10 '17 at 16:40

9000

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asked May 10 '17 at 16:38

JokerMartini

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Does the same thing happen if you save an e.g. PNG? – 9000 May 10 '17 at 16:43
PNG works just fine. I wonder why JPEG does this – JokerMartini May 10 '17 at 16:44
For me even .jpg works with your code. – Rick M. May 10 '17 at 16:46
@RickM. it works for me but the pixel is not a solid Red color and it appears to adjust the surrounding pixels colors as well. – JokerMartini May 10 '17 at 16:57
Relevant - [`Is JPEG lossless when quality is set to 100? `](http://stackoverflow.com/questions/7982409/is-jpeg-lossless-when-quality-is-set-to-100). – Divakar May 10 '17 at 16:59
@JokerMartini It works for me as it should. I have one red pixel at the center. What version of OpenCV/Python/numpy are you using? – Rick M. May 10 '17 at 17:01
both are the latest ones. – JokerMartini May 10 '17 at 17:15
I am using Python 2.7 and OpenCV 3.2.0 and with your code it works like a charm. "both are the latest ones" is dubious. – Rick M. May 10 '17 at 18:25

openCV set color is not displaying Red

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