Add tests. Rise for "P" and "1".

Tests/test_imaging_stretch.py

@@ -0,0 +1,40 @@
+"""
+Tests for ImagingCore.stretch functionality.
+"""
+
+from helper import unittest, PillowTestCase
+
+from PIL import Image
+
+
+im = Image.open("Tests/images/hopper.ppm").copy()
+
+
+class TestImagingStretch(PillowTestCase):
+
+    def test_modes(self):
+        self.assertRaises(ValueError, im.convert("1").im.stretch,
+                          (15, 12), Image.ANTIALIAS)
+        self.assertRaises(ValueError, im.convert("P").im.stretch,
+                          (15, 12), Image.ANTIALIAS)
+        for mode in ["L", "I", "F", "RGB", "RGBA", "CMYK", "YCbCr"]:
+            s = im.convert(mode).im
+            r = s.stretch((15, 12), Image.ANTIALIAS)
+            self.assertEqual(r.mode, mode)
+            self.assertEqual(r.size, (15, 12))
+            self.assertEqual(r.bands, s.bands)
+
+    def test_reduce_filters(self):
+        # There is no Image.NEAREST because im.stretch implementation
+        # is not NEAREST for reduction. It should be removed
+        # or renamed to supersampling.
+        for f in [Image.BILINEAR, Image.BICUBIC, Image.ANTIALIAS]:
+            r = im.im.stretch((15, 12), f)
+            self.assertEqual(r.mode, "RGB")
+            self.assertEqual(r.size, (15, 12))
+
+    def test_enlarge_filters(self):
+        for f in [Image.BILINEAR, Image.BICUBIC, Image.ANTIALIAS]:
+            r = im.im.stretch((764, 414), f)
+            self.assertEqual(r.mode, "RGB")
+            self.assertEqual(r.size, (764, 414))

libImaging/Antialias.c

@@ -95,6 +95,9 @@ ImagingStretch(Imaging imOut, Imaging imIn, int filter)
     if (!imOut || !imIn || strcmp(imIn->mode, imOut->mode) != 0)
         return (Imaging) ImagingError_ModeError();
 
+    if (strcmp(imIn->mode, "P") == 0 || strcmp(imIn->mode, "1") == 0)
+        return (Imaging) ImagingError_ModeError();
+
     /* check filter */
     switch (filter) {
     case IMAGING_TRANSFORM_NEAREST: