feat(raster): IO abstraction with godal implementation; cgo Dockerfile

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/raster/godal_test.go

@@ -0,0 +1,62 @@
+package raster
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+)
+
+func TestGodalIO_RoundTrip(t *testing.T) {
+	rio := NewGodalIO()
+	ctx := context.Background()
+	path := filepath.Join(t.TempDir(), "out.tif")
+	grid := Grid{Width: 10, Height: 7, GeoTransform: [6]float64{100, 30, 0, 200, 0, -30}, ProjectionWKT: "EPSG:32642"}
+
+	w, err := rio.Create(ctx, path, grid, DefaultWriterOptions())
+	if err != nil {
+		t.Fatal(err)
+	}
+	full := make([]int16, 10*7)
+	for i := range full {
+		full[i] = int16(i%6) - 1 // -1..4 (-1 stands in for garbage, not nodata)
+	}
+	full[0] = -9999
+	if err := w.WriteInt16(Window{0, 0, 10, 7}, full); err != nil {
+		t.Fatal(err)
+	}
+	if err := w.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	r, err := rio.Open(ctx, path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer r.Close()
+	g := r.Grid()
+	if g.Width != 10 || g.Height != 7 || g.GeoTransform != grid.GeoTransform || g.ProjectionWKT == "" {
+		t.Fatalf("grid mismatch: %+v", g)
+	}
+	if nd, ok := r.NoData(); !ok || nd != -9999 {
+		t.Fatalf("nodata = %v %v", nd, ok)
+	}
+	dst := make([]float64, 3*2)
+	if err := r.ReadFloat64(Window{X: 8, Y: 5, Width: 2, Height: 2}, dst[:4]); err != nil {
+		t.Fatal(err)
+	}
+	// pixel (8,5) has index 58 -> 58%6-1 = 3 ; (9,5)=59 -> 4 ; (8,6)=68 -> 1 ; (9,6)=69 -> 2
+	want := []float64{3, 4, 1, 2}
+	for i, v := range want {
+		if dst[i] != v {
+			t.Fatalf("pixel %d = %v want %v", i, dst[i], v)
+		}
+	}
+	if !rio.SameGrid(g, grid) {
+		t.Fatal("SameGrid should be true for identical grids")
+	}
+	other := grid
+	other.GeoTransform[0] += 1
+	if rio.SameGrid(g, other) {
+		t.Fatal("SameGrid should be false for shifted origin")
+	}
+}