fix: Handle visualizing COGs with flipped y (origin at the bottom left)

packages/deck.gl-raster/src/raster-tileset/raster-tile-traversal.ts

@@ -614,16 +614,25 @@ function getOverlappingChildRange(
   const childTileWidthCRS = tileWidth * cellSize;
   const childTileHeightCRS = tileHeight * cellSize;
 
-  // Note: we assume top left origin
   const originX = pointOfOrigin[0];
   const originY = pointOfOrigin[1];
 
   // Convert CRS bounds → tile indices
   let minCol = Math.floor((pMinX - originX) / childTileWidthCRS);
   let maxCol = Math.floor((pMaxX - originX) / childTileWidthCRS);
 
-  let minRow = Math.floor((originY - pMaxY) / childTileHeightCRS);
-  let maxRow = Math.floor((originY - pMinY) / childTileHeightCRS);
+  // Row direction depends on cornerOfOrigin:
+  // - topLeft:    row 0 is at originY (max Y), rows increase downward (lower Y)
+  // - bottomLeft: row 0 is at originY (min Y), rows increase upward (higher Y)
+  let minRow: number;
+  let maxRow: number;
+  if (childMatrix.cornerOfOrigin === "bottomLeft") {
+    minRow = Math.floor((pMinY - originY) / childTileHeightCRS);
+    maxRow = Math.floor((pMaxY - originY) / childTileHeightCRS);
+  } else {
+    minRow = Math.floor((originY - pMaxY) / childTileHeightCRS);
+    maxRow = Math.floor((originY - pMinY) / childTileHeightCRS);
+  }
 
   // Clamp to matrix bounds
   minCol = Math.max(0, Math.min(matrixWidth - 1, minCol));

packages/geotiff/src/tile-matrix-set.ts

@@ -119,13 +119,20 @@ export function generateTileMatrixSet(
   for (let idx = 0; idx < overviewsCoarseFirst.length; idx++) {
     const overview = overviewsCoarseFirst[idx]!;
     const { x: matrixWidth, y: matrixHeight } = overview.tileCount;
+    // Clamp tile dimensions to the actual image size. When an overview is
+    // smaller than the tile block size (e.g. a 1×1 pixel image with a 1024
+    // block), using the raw block size as tileWidth would make tileTransform
+    // project pixel (1024,1024) to a CRS coordinate far outside the image
+    // extent, causing proj4 to return null for out-of-range inputs.
+    const tileWidth = Math.min(overview.tileWidth, overview.width);
+    const tileHeight = Math.min(overview.tileHeight, overview.height);
     tileMatrices.push(
       buildTileMatrix(
         String(idx),
         overview.transform,
         mpu,
-        overview.tileWidth,
-        overview.tileHeight,
+        tileWidth,
+        tileHeight,
         matrixWidth,
         matrixHeight,
       ),
@@ -146,8 +153,8 @@ export function generateTileMatrixSet(
       String(geotiff.overviews.length),
       geotiff.transform,
       mpu,
-      geotiff.tileWidth,
-      geotiff.tileHeight,
+      Math.min(geotiff.tileWidth, geotiff.width),
+      Math.min(geotiff.tileHeight, geotiff.height),
       matrixWidth,
       matrixHeight,
     ),

packages/geotiff/tests/integration.test.ts

@@ -9,11 +9,11 @@
  * are intentionally omitted here.
  */
 
+import type { GeoTIFF } from "@developmentseed/geotiff";
 import type { GeoTIFFImage, GeoTIFF as GeotiffJs } from "geotiff";
 import { fromFile } from "geotiff";
 import { afterAll, beforeAll, describe, expect, it } from "vitest";
 import { toBandSeparate } from "../src/array.js";
-import type { GeoTIFF } from "../src/geotiff.js";
 import { fixturePath, loadGeoTIFF } from "./helpers.js";
 
 const FIXTURES = [
@@ -167,3 +167,42 @@ describe("boundless=false edge tile pixel values", () => {
     }
   });
 });
+
+describe("flipped y (positive Y resolution / bottom-left origin)", () => {
+  let ours: GeoTIFF;
+  let ref: GeotiffJs;
+  let refImage: GeoTIFFImage;
+
+  beforeAll(async () => {
+    ours = await loadGeoTIFF(
+      "xjejfvrbm1fbu1ecw-0000000000-0000008192",
+      "source-coop-alpha-earth",
+    );
+    ref = await loadGeoTiffJs(
+      "xjejfvrbm1fbu1ecw-0000000000-0000008192",
+      "source-coop-alpha-earth",
+    );
+    refImage = await ref.getImage();
+  });
+
+  afterAll(() => ref.close());
+
+  it("transform has positive Y resolution (south-up file)", () => {
+    const [, , , , e] = ours.transform;
+    expect(e).toBeGreaterThan(0);
+  });
+
+  it("bbox matches geotiff.js getBoundingBox", () => {
+    // geotiff.js getBoundingBox returns [minX, minY, maxX, maxY]
+    const [minX, minY, maxX, maxY] = refImage.getBoundingBox();
+    expect(ours.bbox[0]).toBeCloseTo(minX!, 3);
+    expect(ours.bbox[1]).toBeCloseTo(minY!, 3);
+    expect(ours.bbox[2]).toBeCloseTo(maxX!, 3);
+    expect(ours.bbox[3]).toBeCloseTo(maxY!, 3);
+  });
+
+  it("bbox minY < maxY (Y increases upward)", () => {
+    const [, minY, , maxY] = ours.bbox;
+    expect(minY).toBeLessThan(maxY);
+  });
+});