. What four steps does the stitching pipeline in this lesson combine, in order?
The pipeline is: SIFT + ratio-test matching (Lesson 20), RANSAC homography (Lessons 23-24), cv2.warpPerspective (Lesson 9), then feathered blending.
. In the final composite, what does the linear feather blend do across the overlap region?
A spatially-varying alpha ramp (same weighted-sum idea as cv2.addWeighted, Lesson 2) is used only within the overlap, so the seam fades smoothly rather than showing a hard cut.
. With no synthetic ground truth available for a real photo pair, how does the lesson measure how good the estimated homography's fit is?
Projecting each inlier through H and measuring distance to its matched point (reprojection error) gives a direct, ground-truth-free measure of geometric fit quality.
. According to the lesson, why might OpenCV's default cv2.StitcherPANORAMA mode bow straight lines when stitching photos of a flat building facade?
PANORAMA mode's spherical warp is suited to pure camera rotation; SCANS mode instead composites with planar homographies directly, matching this lesson's approach.