I find many examples of passing a list of images, and returning a stitched image, but not much information about how these images have beeen stitched together.
In a project, we have a camera fixed still, pointing down, and coveyers pass underneath. The program detects objects and start recording images. However some objects do not enter completely in the image, so we need to capture multiple images and stich then together, but we need to know the position of the stitched image because there are other sensors synchronized with the captured image, and we need to also synchronize their readings within the stitched image (i.e. we know where the reading is within each single capture, but not if captures are stitched together).
In short, given a list of images, how can we find the coordinates of each images relative to each other?
Basically while stiching correspondence between two (or more) images are setup. This is done with some constant key points. After finding those key points the images are warped or transformed & put together, i.e. stitched.
Now those key points could be set/ noted as per a global coordinate system (containing all images). Then one can get the position after stitching too.
Most of the steps are similar to panaroma stitching. You can follow this link for your problem.
Basically, one/some image(s) will be your reference image(s), and you will find the transformation between it and the other ones. These transformations will be your 4*3 homography matrices. Any point in an image can be transformed into another image's coordinate system using these matrices homography. So, you can overcome the occlusion issue that you are trying to solve. Another source for homography.
Related
Im trying to remove the differences between two frames and keep the non-chaning graphics. Would probably repeat the same process with more frames to get more accurate results. My idea is to simplify the frames removing things that won't need to simplify the rest of the process that will do after.
The different frames are coming from the same video so no need to deal with different sizes, orientation, etc. If the same graphic its in another frame but with a different orientation or scale, I would like to also remove it. For example:
Image 1
Image 2
Result (more or less, I suppose that will be uglier but containing a similar information)
One of the problems of this idea is that the source video, even if they are computer generated graphics, is compressed so its not that easy to identify if a change on the tonality of a pixel its actually a change or not.
Im ideally not looking at a pixel level and given the differences in saturation applied by the compression probably is not possible. Im looking for unchaged "objects" in the image. I want to extract the information layer shown on top of whats happening behind it.
During the last couple of days I have tried to achieve it in a Python script by using OpenCV with all kinds of combinations of absdiffs, subtracts, thresholds, equalizeHists, canny but so far haven't found the right implementation and would appreciate any guidance. How would you achieve it?
Im ideally not looking at a pixel level and given the differences in saturation applied by the compression probably is not possible. Im looking for unchaged "objects" in the image. I want to extract the information layer shown on top of whats happening behind it.
This will be extremely hard. You would need to employ proper CV and if you're not an expert in that field, you'll have really hard time.
How about this, forgetting about tooling and libs, you have two images, ie. two equally sized sequences of RGB pixels. Image A and Image B, and the output image R. Allocate output image R of the same size as A or B.
Run a single loop for every pixel, read pixel a and from A and pixel b from B. You get a 3-element (RGB) vector. Find distance between the two vectors, eg. magnitude of a vector (b-a), if this is less than some tolerance, write either a or b to the same offset into result image R. If not, write some default (background) color to R.
You can most likely do this with some HW accelerated way using OpenCV or some other library, but that's up to you to find a tool that does what you want.
I have a database of original images and for each original images there are various cropped versions.
This is an example of how the image look like:
Original
Horizontal Crop
Square Crop
This is a very simple example, but most images are like this, some might taken a smaller section of the original image than others.
I was looking at OpenCV in python but I'm very new to this kind of image processing.
The idea is to be able to save the cropping information separate from the image to save space and then generate all the cropping and different aspect ratio on the fly with a cache system instead.
The method you are looking for is called "template matching". You find examples here
https://docs.opencv.org/trunk/d4/dc6/tutorial_py_template_matching.html
For your problem, given the large images, it might be a good idea to constrain the search space by resizing both images by the same factor. So that searching a position that isn't as precise, but allows then to constrain the actual full pixel sized search to a smaller region around that point.
Okay so i am trying to find homography of a soccer match. What i have till now is
Read images from a folder which is basically many cropped images of a template soccer field. Basically this has images for center circle and penalty lines etc.
Read video stream from a file and crop it into many smaller segments.
Loop inside the images in video stream and inside that another loop for images that i read from folder.
Now in the two images that i get through iteration , i applied a green filter because of my assumption that field is green
Use orb to find points and then find matches.
Now the Problem is that because of players and some noise from croud, i am unable to find proper matches for homography. Also removing them is a problem because that also tends to hide the soccer field lines that i need to calculate the homography on.
Any suggestions on this is greatly appreciated. Also below are some sample code and images that i am using.
"Code being used"
Sample images
Output that i am getting
The image on right of output is a frame from video and that on left is the same sample image that i uploaded after filterGreen function as can be seen from the code.
Finally what i want is for the image to properly map to center circle so i can draw a cube in center, Somewhat similar to "This example" . Thanks in advance for helping me out.
An interesting technique to throw at this problem is RASL. It computes homographies that align stacks of related images. It does not require that you specify corresponding points on the images, but operates directly on the image pixels. It is robust against image occlusions (eg, players moving in the foreground).
I've just released a Python implementation here: https://github.com/welch/rasl
(there are also links there to the original RASL paper, MATLAB implementation, and data).
I am unsure if you'd want to crop the input images to that center circle, or if the entire frames can be aligned. Try both and see.
I am looking at an application where I have two images from a single object (a smartphone) acquired using x-ray. The two images have been acquired at different instant. The intensity content of the two images is thus different and I would like to be able to fuse the two images in order to extract some information about the phones.
In between the two images, the set up have been slightly changed such that the phone is not placed at the same pixel value in the two images. To be able to correctly compare the two images, I would need to translate and rotate the images of the phones such that they overlap as much as possible.
For this I am using python and open cv (cv2). I was thinking to use a thresholding and then find the coordinate of the two thresholded images and use the coordinate to map the yellow image on the red one (or the opposite). The attached image shows what I have obtained so far.
The pseudo code is given in the following:
ret1, thresh1 = cv2.threshold(img1.astype(np.uint8),200,255,cv2.THRESH_BINARY_INV)
ret2, thresh2 = cv2.threshold(template.astype(np.uint8),200,255,cv2.THRESH_BINARY_INV)
plt.figure(1)
plt.subplot(121)
plt.imshow(thresh1)
plt.subplot(122)
plt.imshow(thresh2)
plt.show()
where img1 is one image acquired with the first filter and template is the image acquired with the second filter. One can see that the phones are at different position in the yellow and green images respectivelly.
My question is how to perform the next step. How can I find the coordinate of this thresholded images and then superpose the images of the two phones? Is it the right strategy at all or are there better solutions?
I have been looking at this link on template matching, but for the moment I have had no success.
Hei,
Image-registration did the tricks, thanks! I followed the following tutorial:
image-registration and manage to do what I was looking for.
Thanks!
Greg
I am getting video input from 2 separate cameras with some area of overlap between the output videos. I have tried out a code which combines the video output horizontally. Here is the link for that code:
https://github.com/rajatsaxena/NeuroscienceLab/blob/master/positiontracking/combinevid.py
To explain the problem visually:
The red part shows the overlap region between two image frame. I need the output to look like the second image, with first frame in blue and second frame in green (as shown in third illustration)
A solutions I can think of but unable to implement is, Using SIFT/SURF find out the maximum distance keypoints from both frames and then take the first video frame completely and just pick the non overlapping region from second video frame and horizontally combine them to get the stitched output.
Let me know of any other solutions possible as well. Thanks!
I read this post one hour ago. I tried some really easy approach. Not perfect but in some cases should work well. For example, if you have both cameras on one frame placed side by side.
I took 2 images from the phone like on a picture (color images). Program select Rectangles region from both source images and resize end extract this roi rectangles. The idea is to find the "best" overlapping Rect regions by normalized correlation.
M1 and M2 is mat roi to compare,
matchTemplate(M1, M2, res, TM_CCOEFF_NORMED);
After, I find this overlapping Rect use this to crop source images and combine by hconcat() function together.
My code is in C++ but is really simple to replicate this in python. It is not the best solution but one of the most simple solution. If your cameras are fixed in stable position between themselves. This is a good solution I think.
I hold my phone in hand :)
You can also use this simple approach on video. The speed depends only on the number of rectangle candidate you compare.
You can improve this by smart region to compare selection.
Also, I am thinking about another idea to use optical flow by putting your images from a camera at the same time to sequence behind each other. From the possible overlapping regions in one image extract good features to track and find them in the region of second images.
Surf and sift are great for this but this is the most simple idea on my mind.
Code is Here Code