Fix seam lines in Nile Delta map (#3432)

## Description:
Fix visible seam lines in the Nile Delta map caused by SVG tile
boundaries in the source image. Applied directional elevation blur (1x9
then 9x1 kernels) on land pixels only, preserving rivers and coastlines.

### Before

![before](https://raw.githubusercontent.com/openfrontio/OpenFrontIO/main/map-generator/assets/maps/niledelta/image.png)

### After

![after](https://raw.githubusercontent.com/gabigabogabu/OpenFrontIO/feature/nile-delta-seam-fix/map-generator/assets/maps/niledelta/image.png)

## Checklist
- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

Discord: gabigabogabu

---------

Co-authored-by: FloPinguin <25036848+FloPinguin@users.noreply.github.com>
This commit is contained in:
gabigabogabu
2026-03-15 17:29:26 -03:00
committed by evanpelle
parent b045608c89
commit 54b3a1a7b2
5 changed files with 3 additions and 3 deletions
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