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Image interpolation
Interpolation is how software estimates new pixels when an image is resized; adding pixels is upsampling.
Image interpolation, schematic. Shapes are drawn for illustration.
What the sources say
| Point | Detail | Source |
|---|---|---|
| Nearest neighbour | Repeats pixels, keeping sharp detail but making smooth areas jagged | Wikipedia |
| Bilinear | Reduces contrast at sharp edges, which can be undesirable for line art | Wikipedia |
| Bicubic | Gives substantially better results than bilinear at higher computational cost; smoother tonal gradations | Wikipedia, Adobe |
| Why it is hard | Upsampling is trickier because software must guess how the new pixels should look | Adobe |
| AI upscalers | Must invent or recreate detail that may or may not have been there | Wikipedia |
For wall art
Enlarging a small photo estimates pixels instead of recovering detail, which is why the pixel count of the original still decides the largest good print size.
Where the sources stop
Both pages describe the methods in general terms. Neither gives a quality score or a recommended enlargement limit, so we give none.
Sources
- Wikipedia: Image scaling (fetched 2026-11-12)
- Adobe: how to increase image resolution (fetched 2026-11-12)
Figures from these pages are paraphrased; each page was fetched and read on 2026-11-12. Where two sources differ, both are shown.