[PDFBOX-4631] NPE due to bounding box not being set on PDAppearanceStream

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.16
• Fix Version/s: 2.0.17, 3.0.0 PDFBox
• Component/s: AcroForm
• Environment: Windows 10
• Assignee: Tilman Hausherr
• Reporter: sjoblomj
• Created: 14/Aug/19 11:58
• Updated: 30/Jun/20 06:13
• Resolved: 19/Aug/19 16:27

Description

PDFBox 2.0.16 as well as the current SNAPSNOT version crashes with a NullPointerException. Attached is a small test that triggers the NPE, as well as the PDF.

The stack trace:

java.lang.NullPointerException
    at org.apache.pdfbox.pdmodel.interactive.form.AppearanceGeneratorHelper.applyPadding(AppearanceGeneratorHelper.java:816)
    at org.apache.pdfbox.pdmodel.interactive.form.AppearanceGeneratorHelper.insertGeneratedCombAppearance(AppearanceGeneratorHelper.java:611)
    at org.apache.pdfbox.pdmodel.interactive.form.AppearanceGeneratorHelper.insertGeneratedAppearance(AppearanceGeneratorHelper.java:505)
    at org.apache.pdfbox.pdmodel.interactive.form.AppearanceGeneratorHelper.setAppearanceContent(AppearanceGeneratorHelper.java:374)
    at org.apache.pdfbox.pdmodel.interactive.form.AppearanceGeneratorHelper.setAppearanceValue(AppearanceGeneratorHelper.java:223)
    at org.apache.pdfbox.pdmodel.interactive.form.PDTextField.constructAppearances(PDTextField.java:264)
    at org.apache.pdfbox.pdmodel.interactive.form.PDTerminalField.applyChange(PDTerminalField.java:228)
    at org.apache.pdfbox.pdmodel.interactive.form.PDTextField.setValue(PDTextField.java:219)
    at PdfBoxTest.reformatFields(PdfBoxTest.java:67)
    at PdfBoxTest.flattenDocument(PdfBoxTest.java:52)
    at PdfBoxTest.flatten(PdfBoxTest.java:42)
    at PdfBoxTest.fileWithStrangeContent(PdfBoxTest.java:27)

 

The origin of the error seems to be in AppearanceGeneratorHelper.setAppearanceValue(). A PDAppearanceStream is created, but a bounding box is only set for it if this is false: if (appearance != null && appearance.isStream()). In my case, the conditional is true, and PDFBox takes a path where no bounding box gets set.

The following could be a solution, but I'm not very fluent in the inner workings of PDFs, and it's not directly obvious from looking at the code that this is a good approach.

diff --git a/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/interactive/form/AppearanceGeneratorHelper.java b/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/interactive/form/AppearanceGeneratorHelper.java
index dc2825d4c..a82236069 100644
--- a/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/interactive/form/AppearanceGeneratorHelper.java
+++ b/pdfbox/src/main/java/org/apache/pdfbox/pdmodel/interactive/form/AppearanceGeneratorHelper.java
@@ -201,6 +201,7 @@ class AppearanceGeneratorHelper
                 if (appearance != null && appearance.isStream())
                 {
                     appearanceStream = appearance.getAppearanceStream();
+                    setBoundingBoxOnAppearanceStream(widget, appearanceStream);
                 }
                 else
                 {
@@ -235,15 +236,9 @@ class AppearanceGeneratorHelper

         // Calculate the entries for the bounding box and the transformation matrix
         // settings for the appearance stream
-        int rotation = resolveRotation(widget);
-        PDRectangle rect = widget.getRectangle();
-        Matrix matrix = Matrix.getRotateInstance(Math.toRadians(rotation), 0, 0);
-        Point2D.Float point2D = matrix.transformPoint(rect.getWidth(), rect.getHeight());
+        setBoundingBoxOnAppearanceStream(widget, appearanceStream);

-        PDRectangle bbox = new PDRectangle(Math.abs((float) point2D.getX()), Math.abs((float) point2D.getY()));
-        appearanceStream.setBBox(bbox);
-
-        AffineTransform at = calculateMatrix(bbox, rotation);
+        AffineTransform at = calculateMatrix(appearanceStream.getBBox(), resolveRotation(widget));
         if (!at.isIdentity())
         {
             appearanceStream.setMatrix(at);
@@ -252,7 +247,17 @@ class AppearanceGeneratorHelper
         appearanceStream.setResources(new PDResources());
         return appearanceStream;
     }
-
+
+    private void setBoundingBoxOnAppearanceStream(PDAnnotationWidget widget, PDAppearanceStream appearanceStream) {
+        int rotation = resolveRotation(widget);
+        PDRectangle rect = widget.getRectangle();
+        Matrix matrix = Matrix.getRotateInstance(Math.toRadians(rotation), 0, 0);
+        Point2D.Float point2D = matrix.transformPoint(rect.getWidth(), rect.getHeight());
+
+        PDRectangle bbox = new PDRectangle(Math.abs((float) point2D.getX()), Math.abs((float) point2D.getY()));
+        appearanceStream.setBBox(bbox);
+    }
+
     private PDDefaultAppearanceString getWidgetDefaultAppearanceString(PDAnnotationWidget widget) throws IOException
     {
         COSString da = (COSString) widget.getCOSObject().getDictionaryObject(COSName.DA);