CODEWITHSUNDEEP
pythonopencvscikit-learn
Daniel
Daniel

Reputation: 4342

Determine The Orientation Of An Image

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I am trying to determine the orientation of the following image. Given an image at random between 140x140 to 150X150 pixels with no EXIF data. Is there a method to define each image as 0, 90, 180 or 270 degrees so that when I get an image of a particular orientation I can match that with my predefined images? I've looked into feature matching with opencv using the following tutorial, and it works correctly. Identify the images as the same no matter its orientation, but I have no clue how to tell them apart.

Upvotes: 3

Views: 3579

Answers (2)

PhilLab
PhilLab

Reputation: 5007

I've looked into feature matching with opencv using the following tutorial, and it works correctly

So you could establish a valid match between an image of unknown rotation and an image in your database? And the latter one is of a known rotation (i.e. upright)?

In this case you can compute a transformation matrix:

  • either a homography which defines a full planar transformation (use cv::findHomography)
  • or an affine transform which expresses translation, rotation and scaling and thus seems best for your needs (use cv::estimateRigidTransform with fullAffine=true). You can find more about affine transformations here

If you don't have any known image then this task seems mathematically unsolvable but you could use something like an Artificial-Neural-Network-based heuristic which seems like a very research-intensive project.

Upvotes: 1

Rachel L
Rachel L

Reputation: 327

If you have the random image somewhere (say, you're trying to match a certain image to a list of images you have), you could try taking the difference of your random image and your list of known images four times for each image, rotating the known image each time by 90 deg. Whichever one is closer to zero should be what you want.

If the image sizes of both your new image and the list of images are the same, you might also be able to just compare the keypoint distance differences (if the image is a match but all the keypoints are all rotated a quadrant clockwise from each other, then it's 90 deg off etc).

If you have no idea what that random image is supposed to be, I can't really think of any way to figure that out, unless you know for sure that a blob of light blue is supposed to be the sky. As far as I know, there's got to be something that you know to be up in order to determine what up is.

Upvotes: 0

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