From bd3357e5c6dee34a6e458a2ac956643468f8fb2c Mon Sep 17 00:00:00 2001
From: Wentao Kuang <wkuang@linz.govt.nz>
Date: Fri, 6 Dec 2024 09:54:43 +1300
Subject: [PATCH] feat(config): Add resizeKernel into the config tileset then
 disable fastShrinkOnLoad. BM-1146 (#3377)

### Motivation
As raster Topo map got edge effects on low zoom levels usually below
zoom 6, like following.

![image](https://github.com/user-attachments/assets/44a0e388-a00b-4d70-bfda-62414930dab8)

We have tests that with output resize kernel of `mitchell` and disable
the fastShrinkOnLoad for lower scales levels will fix this problem.

![image](https://github.com/user-attachments/assets/dcf1af02-16b8-4738-81b7-dc4c5ef255ab)

### Modifications

- Add the resiseKernel setting in the config bundle, so that we can
bundle it into server.
- disable `fastShrinkOnLoad` for the `resize.scale`less than 0.125.

- Not fix yet: The virtual tileset for `topo-raster-50k` and
`topo-raster-250k` won't fix as we can't propagate the resize kernel
from combined tileset -> imagery config -> virtual tileset. Unless we
add optional resizeKernal property for imagery config.

### Verification
Local test.

![image](https://github.com/user-attachments/assets/4a15d740-46c7-4592-a238-35864b701b77)
---
 packages/config-loader/src/json/json.config.ts    | 1 +
 packages/config-loader/src/json/parse.tile.set.ts | 5 ++++-
 packages/config/src/config/tile.set.ts            | 2 +-
 packages/tiler-sharp/src/index.ts                 | 7 ++++++-
 packages/tiler/src/raster.ts                      | 2 +-
 5 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/packages/config-loader/src/json/json.config.ts b/packages/config-loader/src/json/json.config.ts
index bd4eb7111..c328583b9 100644
--- a/packages/config-loader/src/json/json.config.ts
+++ b/packages/config-loader/src/json/json.config.ts
@@ -247,6 +247,7 @@ export class ConfigJson {
     if (tileSet.type === TileSetType.Raster) {
       if (ts.outputs) tileSet.outputs = ts.outputs;
       if (ts.background) tileSet.background = ts.background;
+      if (ts.resizeKernel) tileSet.resizeKernel = ts.resizeKernel;
     }
 
     if (ts.format) {
diff --git a/packages/config-loader/src/json/parse.tile.set.ts b/packages/config-loader/src/json/parse.tile.set.ts
index 040c08e99..2a641df6d 100644
--- a/packages/config-loader/src/json/parse.tile.set.ts
+++ b/packages/config-loader/src/json/parse.tile.set.ts
@@ -1,4 +1,4 @@
-import { ConfigTileSetOutputParser, parseRgba, TileSetType } from '@basemaps/config';
+import { ConfigTileSetOutputParser, parseRgba, TileResizeKernel, TileSetType } from '@basemaps/config';
 import { z } from 'zod';
 
 export function validateColor(str: string): boolean {
@@ -57,6 +57,8 @@ const zLayerConfig = z
     },
   );
 
+const TileResizeKernel = z.enum(['nearest', 'mitchell', 'lanczos3', 'lanczos2']);
+
 export const zTileSetConfig = z.object({
   type: z.nativeEnum(TileSetType),
   id: z.string(),
@@ -68,6 +70,7 @@ export const zTileSetConfig = z.object({
   minZoom: zZoom.optional(),
   maxZoom: zZoom.optional(),
   format: z.string().optional(),
+  resizeKernel: z.object({ in: TileResizeKernel, out: TileResizeKernel }).optional(),
   outputs: z.array(ConfigTileSetOutputParser).optional(),
 });
 
diff --git a/packages/config/src/config/tile.set.ts b/packages/config/src/config/tile.set.ts
index 07aa1e505..0642f62f3 100644
--- a/packages/config/src/config/tile.set.ts
+++ b/packages/config/src/config/tile.set.ts
@@ -31,7 +31,7 @@ export interface ConfigLayer extends Partial<Record<EpsgCode, string>> {
   maxZoom?: number;
 }
 
-export type TileResizeKernel = 'nearest' | 'lanczos3' | 'lanczos2';
+export type TileResizeKernel = 'nearest' | 'mitchell' | 'lanczos3' | 'lanczos2';
 
 export interface ConfigTileSetBase extends ConfigBase {
   /** Human friendly display name for the tileset */
diff --git a/packages/tiler-sharp/src/index.ts b/packages/tiler-sharp/src/index.ts
index 6ae79bcf1..ca98880af 100644
--- a/packages/tiler-sharp/src/index.ts
+++ b/packages/tiler-sharp/src/index.ts
@@ -144,7 +144,12 @@ export class TileMakerSharp implements TileMaker {
 
     if (resize) {
       const resizeOptions = { fit: Sharp.fit.cover, kernel: resize.scaleX > 1 ? resizeKernel.in : resizeKernel.out };
-      sharp.resize(resize.width, resize.height, resizeOptions);
+      if (resize.scale <= 0.1251) {
+        // If the scale is less than 0.125, we need to disable fastShrinkOnLoad to prevent edge artifacts for topo raster map
+        sharp.resize(resize.width, resize.height, { ...resizeOptions, fastShrinkOnLoad: false });
+      } else {
+        sharp.resize(resize.width, resize.height, resizeOptions);
+      }
     }
 
     if (crop) sharp.extract({ top: crop.y, left: crop.x, width: crop.width, height: crop.height });
diff --git a/packages/tiler/src/raster.ts b/packages/tiler/src/raster.ts
index 7278549b7..4ad658628 100644
--- a/packages/tiler/src/raster.ts
+++ b/packages/tiler/src/raster.ts
@@ -7,7 +7,7 @@ export interface TileMaker {
   compose(ctx: TileMakerContext): Promise<{ buffer: Buffer; metrics: Metrics }>;
 }
 
-export type ResizeKernelType = 'nearest' | 'lanczos3' | 'lanczos2';
+export type ResizeKernelType = 'nearest' | 'mitchell' | 'lanczos3' | 'lanczos2';
 export type TileMakerResizeKernel = { in: ResizeKernelType; out: ResizeKernelType };
 
 export interface TileMakerContext {