Correct scale factor adjustments

We were erroneously setting matrix scaling factor to zero for rotation matrices.

Addresses issue 3591.

src/__init__.py

@@ -18928,8 +18928,10 @@ def jm_lineart_stroke_path( dev, ctx, path, stroke, ctm, colorspace, color, alph
     try:
         assert isinstance( ctm, mupdf.fz_matrix)
         dev.pathfactor = 1
-        if abs(ctm.a) == abs(ctm.d):
+        if ctm.a != 0 and abs(ctm.a) == abs(ctm.d):
             dev.pathfactor = abs(ctm.a)
+        elif ctm.b != 0 and abs(ctm.b) == abs(ctm.c):
+            dev.pathfactor = abs(ctm.b)
         dev.ctm = mupdf.FzMatrix( ctm)  # fz_concat(ctm, dev_ptm);
         dev.path_type = trace_device_STROKE_PATH
 

src/extra.i

@@ -2647,8 +2647,12 @@ jm_lineart_stroke_path(fz_context *ctx, fz_device *dev_, const fz_path *path,
     //printf("extra.jm_lineart_stroke_path(): dev->seqno=%zi\n", dev->seqno);
     int i;
     dev->pathfactor = 1;
-    if (fz_abs(ctm.a) == fz_abs(ctm.d)) {
+    if (ctm.a != 0 && fz_abs(ctm.a) == fz_abs(ctm.d)) {
         dev->pathfactor = fz_abs(ctm.a);
+    } else {
+        if (ctm.b != 0 && fz_abs(ctm.b) == fz_abs(ctm.c)) {
+            dev->pathfactor = fz_abs(ctm.b);
+        }
     }
     dev->ctm = ctm; // fz_concat(ctm, trace_device_ptm);
     dev->path_type = STROKE_PATH;

tests/test_drawings.py

@@ -169,7 +169,7 @@ def test_2556():
     # following contains an incomplete clip
     c = b"q 50 697.6 400 100.0 re W n q 0 0 m W n Q "
     xref = doc.get_new_xref()  # prepare /Contents object for page
-    doc.update_object(xref,"<<>>")  # new xref now is a dictionary
+    doc.update_object(xref, "<<>>")  # new xref now is a dictionary
     doc.update_stream(xref, c)  # store drawing commands
     page.set_contents(xref)  # give the page this xref as /Contents
     # following will bring down interpreter if fix not installed
@@ -218,3 +218,13 @@ def test_3207():
     p11 = items[5][2]
     assert p0 == p5
     assert p6 == p11
+
+
+def test_3591():
+    """Confirm correct scaling factor for rotation matrices."""
+    filename = os.path.join(scriptdir, "resources", "test-3591.pdf")
+    doc = pymupdf.open(filename)
+    page = doc[0]
+    paths = page.get_drawings()
+    for p in paths:
+        assert p["width"] == 15