watch: embed local images in PNG previews

ci/release/changelogs/next.md

@@ -33,6 +33,8 @@
 
 #### Bugfixes ⛑️
 
+- watch: embed local images in PNG watch previews instead of treating their URLs
+  as board navigation. [#2945](https://github.com/d2lang/d2/issues/2945)
 - compiler:
   - Limit combined map/array nesting to 128. [#2894](https://github.com/d2lang/d2/pull/2894)
   - Honor cancellation during parsing and IR compilation, and prevent `d2 fmt`

d2cli/main.go

@@ -1019,15 +1019,16 @@ func _renderWithPNGEncoder(ctx context.Context, ms *xmain.State, opts d2svg.Rend
 		cacheImages := ms.Env.Getenv("IMG_CACHE") == "1"
 		if opts.MasterID == "" {
 			written, err := writePNGWithStatus(ctx, ms, outputPath, func(output io.Writer) error {
-				return renderPNGToWriter(ctx, inputPath, cacheImages, diagram, *renderOpts, pngEncoder, output)
+				svg, err = renderPNGToWriter(ctx, inputPath, cacheImages, diagram, *renderOpts, pngEncoder, output, svg)
+				return err
 			})
 			if err != nil {
 				return svg, written, err
 			}
 			return svg, written, nil
 		}
 		// Animated SVG composition only needs validation, not retained PNG bytes.
-		err = renderPNGToWriter(ctx, inputPath, cacheImages, diagram, *renderOpts, pngEncoder, io.Discard)
+		svg, err = renderPNGToWriter(ctx, inputPath, cacheImages, diagram, *renderOpts, pngEncoder, io.Discard, svg)
 		return svg, false, err
 	}
 

d2cli/raster_png_output.go

@@ -28,17 +28,28 @@ func pngFrameOptions() d2raster.FrameOptions {
 	return options
 }
 
-func renderPNGToWriter(ctx context.Context, inputPath string, cacheImages bool, diagram *d2target.Diagram, opts d2svg.RenderOpts, encoder *rasterPNGEncoder, output io.Writer) error {
-	document, err := buildScene(ctx, inputPath, cacheImages, diagram, opts)
+func renderPNGToWriter(ctx context.Context, inputPath string, cacheImages bool, diagram *d2target.Diagram, opts d2svg.RenderOpts, encoder *rasterPNGEncoder, output io.Writer, preview []byte) ([]byte, error) {
+	assetOptions, err := sceneAssetOptions(ctx, inputPath, cacheImages)
 	if err != nil {
-		return err
+		return preview, err
+	}
+	defer assetOptions.Resolver.CloseIdleConnections()
+	document, err := buildSceneWithAssets(ctx, diagram, opts, assetOptions)
+	if err != nil {
+		return preview, err
 	}
 	var localEncoder rasterPNGEncoder
 	if encoder == nil {
 		encoder = &localEncoder
 		defer localEncoder.close()
 	}
-	return encodePNGBands(ctx, output, document, &encoder.bands)
+	if err := encodePNGBands(ctx, output, document, &encoder.bands); err != nil {
+		return preview, err
+	}
+	if len(preview) != 0 {
+		return bundleRasterPreview(ctx, assetOptions.Resolver, preview)
+	}
+	return preview, nil
 }
 
 func encodePNGBands(ctx context.Context, output io.Writer, document *d2scene.Document, encoder *rasterPNGBandEncoder) error {

d2cli/raster_png_output_test.go

@@ -42,7 +42,7 @@ func TestPNGStreamMatchesCompleteFrame(t *testing.T) {
 				t.Fatal(err)
 			}
 			var got bytes.Buffer
-			if err := renderPNGToWriter(context.Background(), "-", false, diagram, opts, &encoder, &got); err != nil {
+			if _, err := renderPNGToWriter(context.Background(), "-", false, diagram, opts, &encoder, &got, nil); err != nil {
 				t.Fatalf("shadow=%v scale=%v: %v", shadow, scale, err)
 			}
 			// Identical encoded bytes also verify PNG filtering across strip
@@ -90,7 +90,7 @@ func TestPNGStreamDiagramFixtures(t *testing.T) {
 					t.Fatal(err)
 				}
 				var got bytes.Buffer
-				if err := renderPNGToWriter(context.Background(), "-", false, &diagram, opts, nil, &got); err != nil {
+				if _, err := renderPNGToWriter(context.Background(), "-", false, &diagram, opts, nil, &got, nil); err != nil {
 					t.Fatal(err)
 				}
 				assertPNGOutputPixels(t, got.Bytes(), want)

d2cli/raster_test.go

@@ -634,6 +634,45 @@ func TestFolderOnlyPNGReturnsFirstBoardPreview(t *testing.T) {
 	}
 }
 
+func TestPNGWatchPreviewEmbedsLocalImages(t *testing.T) {
+	directory := t.TempDir()
+	inputPath := filepath.Join(directory, "input.d2")
+	asset := testSolidPNG(t, color.NRGBA{R: 0x12, G: 0x34, B: 0x56, A: 0xff})
+	if err := os.WriteFile(filepath.Join(directory, "asset.png"), asset, 0o644); err != nil {
+		t.Fatal(err)
+	}
+	assetURL, err := url.Parse("asset.png")
+	if err != nil {
+		t.Fatal(err)
+	}
+	env := xos.NewEnv(nil)
+	state := &xmain.State{Env: env, Log: cmdlog.NewTB(env, t), PWD: directory}
+	outputPath := filepath.Join(directory, "output.png")
+	boards, written, err := render(
+		context.Background(), state, 0,
+		d2svg.RenderOpts{Pad: go2.Pointer(int64(0)), Scale: go2.Pointer(1.0)},
+		inputPath, outputPath, false, false, nil,
+		rasterImageDiagram(assetURL), PNG, "", true,
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !written || len(boards) != 1 {
+		t.Fatalf("PNG written/preview count = %t/%d", written, len(boards))
+	}
+	want := "data:image/png;base64," + base64.StdEncoding.EncodeToString(asset)
+	if !bytes.Contains(boards[0], []byte(want)) || bytes.Contains(boards[0], []byte(`href="asset.png"`)) {
+		t.Fatal("PNG watch preview did not embed its local image")
+	}
+	output, err := os.ReadFile(outputPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := png.Decode(bytes.NewReader(output)); err != nil {
+		t.Fatalf("PNG export: %v", err)
+	}
+}
+
 func TestBundleGIFPreviewEmbedsLocalImages(t *testing.T) {
 	directory := t.TempDir()
 	inputPath := filepath.Join(directory, "input.d2")