Consider the following statements with respect to approaches to fill area on…
2019
Consider the following statements with respect to approaches to fill area on raster systems:
𝑃: To determine the overlap intervals for scan lines that cross the area
𝑄: To start from a given interior position and pain outward from this point until we encounter the specified boundary conditions.
Select the correct answer from the options given below:
- A.
𝑃 only
- B.
𝑄 only
- C.
Both 𝑃 and 𝑄
- D.
Neither 𝑃 nor 𝑄
Attempted by 72 students.
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Correct answer: C
Answer: Both statements are correct — both approaches are used to fill areas on raster systems.
Scan-line fill (determine overlap intervals for scan lines):
For each horizontal scan line, compute intersections with the region boundary, sort the intersection x-coordinates, pair them, and fill the pixel spans between each pair.
Advantages: efficient for polygons with long horizontal spans and requires fewer per-pixel boundary checks.
Flood-fill (start from an interior point and paint outward):
Begin at a known interior pixel and iteratively (using a stack or queue) expand to neighboring pixels (4- or 8-connected) until boundary pixels stop further expansion.
Advantages: simple to implement and works for arbitrary shapes; disadvantages: can be memory- or recursion-intensive for large regions.
Conclusion: Both the scan-line interval method and the flood-fill method are valid approaches for filling areas on raster displays, so the correct choice is the one that states both are true.