input parameter filtering

Tests/test_image_resample.py

@@ -8,11 +8,29 @@ class TestImagingCoreResize(PillowTestCase):
         xsize = 0x100000008 // 4
         ysize = 1000 # unimportant
         try:
-            im.im.resize((xsize, ysize), Image.LINEAR) # any resampling filter will do here
+            # any resampling filter will do here
+            im.im.resize((xsize, ysize), Image.LINEAR) 
             self.fail("Resize should raise MemoryError on invalid xsize")
         except MemoryError:
             self.assertTrue(True, "Should raise MemoryError")
 
+    def test_invalid_size(self):
+        im = hopper()
+
+        im.resize((100,100))
+        self.assertTrue(True, "Should not Crash")
+        
+        try:
+            im.resize((-100,100))
+            self.fail("Resize should raise a value error on x negative size")
+        except ValueError:
+            self.assertTrue(True, "Should raise ValueError")
+
+        try:
+            im.resize((100,-100))
+            self.fail("Resize should raise a value error on y negative size")
+        except ValueError:
+            self.assertTrue(True, "Should raise ValueError")
 
 if __name__ == '__main__':
     unittest.main()

_imaging.c

@@ -1532,6 +1532,10 @@ _resize(ImagingObject* self, PyObject* args)
 
     imIn = self->image;
 
+    if (xsize < 1 || ysize < 1) {
+        return ImagingError_ValueError("height and width must be > 0");
+    }
+
     if (imIn->xsize == xsize && imIn->ysize == ysize) {
         imOut = ImagingCopy(imIn);
     }