Image rotation: forward versus inverse mapping
WHAT IT TESTS: geometric warping mechanics. OUTLINE: forward mapping sends source pixels to non-integer destinations, leaving holes and overlaps; inverse mapping iterates over output pixels, finds the source location, and interpolates.
WHAT IT TESTS: whether you understand resampling on a discrete grid. ANSWER OUTLINE: a rotation maps each pixel to a new location that is generally non-integer; forward mapping pushes source pixels outward, so the output grid gets holes where no source lands and collisions where several do. Inverse mapping instead iterates over every output pixel, applies the inverse transform to find the corresponding source coordinate, and interpolates (e.g. bilinear) from neighboring source pixels. RED FLAG: claiming forward mapping produces a gapless image.
Read the original → interview
- #image-rotation
- #inverse-mapping
- #interpolation
- #warping
- #resampling
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