test(chromium): cover header and footer image deduplication

test/integration/scenario/images.go

@@ -0,0 +1,72 @@
+package scenario
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+func (s *scenario) thePdfShouldReuseImageXObjects(ctx context.Context, name string, images, pages int) error {
+	path := filepath.Join(s.workdir, s.resp.Header().Get("Gotenberg-Trace"), name)
+	if _, err := os.Stat(path); err != nil {
+		return fmt.Errorf("stat PDF %q: %w", path, err)
+	}
+
+	cmd := []string{"pdfimages", "-list", filepath.Base(path)}
+	output, err := execCommandInIntegrationToolsContainer(ctx, cmd, path)
+	if err != nil {
+		return fmt.Errorf("exec %q: %w", cmd, err)
+	}
+
+	return checkImageXObjectReuse(output, images, pages)
+}
+
+func checkImageXObjectReuse(output string, images, pages int) error {
+	lines := strings.Split(strings.TrimSpace(output), "\n")
+	if len(lines) < 2 || !strings.HasPrefix(strings.TrimSpace(lines[0]), "page") {
+		return fmt.Errorf("invalid pdfimages -list output: %q", output)
+	}
+
+	objects := make(map[[2]int]struct{})
+	imagesPerPage := make(map[int]int)
+	for _, line := range lines[2:] {
+		fields := strings.Fields(line)
+		if len(fields) < 12 {
+			return fmt.Errorf("invalid pdfimages -list row: %q", line)
+		}
+
+		page, err := strconv.Atoi(fields[0])
+		if err != nil {
+			return fmt.Errorf("parse image page %q: %w", fields[0], err)
+		}
+		if page < 1 || page > pages {
+			return fmt.Errorf("image on page %d outside expected range 1-%d", page, pages)
+		}
+
+		// pdfimages lists appearances, including repeated references to the
+		// same image. Columns 11 and 12 identify the underlying PDF object.
+		var ref [2]int
+		for i := range ref {
+			ref[i], err = strconv.Atoi(fields[10+i])
+			if err != nil {
+				return fmt.Errorf("parse image object ID in %q: %w", line, err)
+			}
+		}
+		objects[ref] = struct{}{}
+		imagesPerPage[page]++
+	}
+
+	for page := 1; page <= pages; page++ {
+		if imagesPerPage[page] != images {
+			return fmt.Errorf("expected %d image appearance(s) on page %d, but actual is %d", images, page, imagesPerPage[page])
+		}
+	}
+	if len(objects) != images {
+		return fmt.Errorf("expected %d unique image XObject(s) shared across %d page(s), but actual is %d", images, pages, len(objects))
+	}
+
+	return nil
+}