Project 5a: Image Warping & Mosaicing¶
Harish Palani (CS 194-26)
1. Shoot the Pictures
For this project, I used the following three perspectives captured at a local park here in Portland, Oregon. These shots all revolve around a basketball hoop, which forms a key focal point to be used when aligning images for stitching.
I chose to blend the center and right perspectives, zeroing in on three objects present in each perspective: the basketball hoop, the lamppost, and a street sign in the background. The final points selected for alignment can be seen below.
2. Recover Homographies
With correspondences defined by hand as shown above, I had to recover the parameters of the transformation between the two images to properly inform subsequent warping & rectification steps. The resulting homography matrix H is shown below.
3. Image Warping & Rectification
Warping and rectification algorithms for this part were tested on the right perspective displayed above, with the warped output ultimately blended wtih the center perspective in the final mosaic. Results for this section are shown below.
4. From Image to Mosaic
To form a realistic mosaic from these two perspectives, I kept the center perspective unchanged and blended it with the warped version of right perspective as shown above. This yields the following raw output — not bad!
Cropping yields the following final output, with minimal artifacts at first glance. Upon closer inspection, the misaligned windows and lamppost in the background — along the seam of the two perspectives — reveal themselves to be perhaps the most glaring errors present.
What you've learned (so far): This has been an incredibly interesting project with many practical lessons. Perhaps the coolest of all has been developing an general understanding of homographies and mosaicing, both of which lie at the core of the panorama feature used on smartphone cameras every day — not to mention photo spheres, Google Street View, and other incredible innovations!