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cv::imread - Camera orientation problem

asked 2016-01-08 17:33:26 -0500

Sid23 gravatar image

updated 2016-01-09 10:05:40 -0500

I'm following this guide here to try out CLAHE in Python, so I have the following code:

import numpy as np
import cv2

img = cv2.imread('t1.JPG',0)
clahe = cv2.createCLAHE(clipLimit=2.0, tileGridSize=(8,8))
cl1 = clahe.apply(img)

cv2.imwrite('t1-clahe.JPG',cl1)

Before (t1.JPG):
t1.JPG

After (t1-clahe.JPG):
image description

So, if you see the links provided, the image has been reshaped. There doesn't seem to be any indication in the guide that this should happen. Am I missing something here? I don't want to reshape the image.

Funny thing is that if I output the shape of the image then there seems to be no change. I get the following:

Before: (2448, 3264)
After: (2448, 3264)

But if you look at the after image, it has clearly been reshaped. I noticed another thing. This problem is only happening with images taken from my iPhone 5S. I tried other images and they did not have the same issue. I tried to find differences between the images that are being reshaped and ones that aren't. So, I noticed the following difference:

reshaped    : JPEG image data, EXIF standard 2.21
not reshaped: JPEG image data, JFIF standard 1.01

Any help with this problem would be greatly appreciated.

OpenCV version being used: 2.4.8

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Comments

2

i do not see any reshape here ?

berak gravatar imageberak ( 2016-01-09 03:51:40 -0500 )edit
1

also, please, for the future, spare us such ridiculous large images

berak gravatar imageberak ( 2016-01-09 03:52:51 -0500 )edit

I guess 'reshape' wasn't the correct terminology for this problem. What I meant was that the 'orientation' has changed. As for the images, I didn't think that they would be imbedded into the notification emails since I provided external links

Sid23 gravatar imageSid23 ( 2016-01-09 09:50:04 -0500 )edit

maybe we should rephrase the whole question (as CLAHE has absolutely nothing to do with it) to "problems with image orientation due to EXIF headers" or the like ?

berak gravatar imageberak ( 2016-01-09 10:03:30 -0500 )edit

@berak i was editing the question when you were commenting. @Sid23 i edited label of the question but it will be better if you rephrase the whole question.

sturkmen gravatar imagesturkmen ( 2016-01-09 10:08:15 -0500 )edit

imho, it's perfect, already ;)

berak gravatar imageberak ( 2016-01-09 10:20:05 -0500 )edit

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answered 2016-01-09 06:11:52 -0500

updated 2016-01-09 06:45:55 -0500

just to clarify the question

test code

#include "opencv2/highgui.hpp"

using namespace cv;

int main( int argc, char** argv )
{
    Mat src1 = imread( "t1.JPG" );
    Mat src2 = imread( "t1-clahe2.JPG" );

    imwrite("imwrite-t1.jpg",src1);
    imwrite("imwrite-t1-clahe2.jpg",src2);

    imshow("t1.JPG",src1);
    imshow("t1-clahe2.JPG",src2);
    waitKey(0);

    return 0;
}

screenshot of Windows7 Explorer window image description

EDIT :

Camera orientation handling is newly added to OpenCV

my result is as following reverting Camera orientation handling

image description

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Comments

1

yes, you are right. It is due to the camera orientation issue. My version of OpenCV doesn't handle orientation properly. I've found a workaround though, which is good enough for my purposes. Thank you for your help.

Sid23 gravatar imageSid23 ( 2016-01-09 09:46:53 -0500 )edit

Windows7 also doesn't handle orientation properly. what about Windows8,Windows10 and Linux?

sturkmen gravatar imagesturkmen ( 2016-01-09 10:23:44 -0500 )edit

Linux reads the exif data correctly and expects users to handle that, which is actually how it should be.

StevenPuttemans gravatar imageStevenPuttemans ( 2016-01-11 06:58:07 -0500 )edit
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Asked: 2016-01-08 15:34:31 -0500

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Last updated: Jan 09 '16