add roi argument to Image.resize() method

constraints check

PIL/Image.py

@@ -1519,7 +1519,7 @@ class Image(object):
             return self.pyaccess.putpixel(xy, value)
         return self.im.putpixel(xy, value)
 
-    def resize(self, size, resample=NEAREST):
+    def resize(self, size, resample=NEAREST, roi=None):
         """
         Returns a resized copy of this image.
 
@@ -1555,7 +1555,10 @@ class Image(object):
         if self.mode == 'RGBA':
             return self.convert('RGBa').resize(size, resample).convert('RGBA')
 
-        return self._new(self.im.resize(size, resample))
+        if roi is None:
+            roi = (0, 0) + self.size
+
+        return self._new(self.im.resize(size, resample, roi))
 
     def rotate(self, angle, resample=NEAREST, expand=0):
         """

Tests/test_image_resample.py

@@ -348,5 +348,36 @@ class CoreResampleCoefficientsTest(PillowTestCase):
         self.assertEqual(histogram[0x100 * 3 + 0xff], 0x10000) # fourth channel
 
 
+class CoreResampleRoiTest(PillowTestCase):
+    def test_wrong_arguments(self):
+        im = hopper()
+        for resample in (Image.LINEAR, Image.BOX, Image.BILINEAR, Image.HAMMING,
+                Image.BICUBIC, Image.LANCZOS):
+            im.resize((32, 32), resample, (0, 0, im.width, im.height))
+            im.resize((32, 32), resample, (20, 20, im.width, im.height))
+
+            with self.assertRaisesRegexp(TypeError, "must be sequence of length 4"):
+                im.resize((32, 32), resample, (im.width, im.height))
+
+            with self.assertRaisesRegexp(ValueError, "can't be negative"):
+                im.resize((32, 32), resample, (-20, 20, 100, 100))
+            with self.assertRaisesRegexp(ValueError, "can't be negative"):
+                im.resize((32, 32), resample, (20, -20, 100, 100))
+
+            with self.assertRaisesRegexp(ValueError, "can't be empty"):
+                im.resize((32, 32), resample, (20, 20, 20, 100))
+            with self.assertRaisesRegexp(ValueError, "can't be empty"):
+                im.resize((32, 32), resample, (100, 20, 20, 100))
+            with self.assertRaisesRegexp(ValueError, "can't be empty"):
+                im.resize((32, 32), resample, (20, 20, 100, 20))
+            with self.assertRaisesRegexp(ValueError, "can't be empty"):
+                im.resize((32, 32), resample, (20, 100, 100, 20))
+
+            with self.assertRaisesRegexp(ValueError, "can't exceed"):
+                im.resize((32, 32), resample, (0, 0, im.width + 1, im.height))
+            with self.assertRaisesRegexp(ValueError, "can't exceed"):
+                im.resize((32, 32), resample, (0, 0, im.width, im.height + 1))
+
+
 if __name__ == '__main__':
     unittest.main()

_imaging.c

@@ -1534,15 +1534,32 @@ _resize(ImagingObject* self, PyObject* args)
 
     int xsize, ysize;
     int filter = IMAGING_TRANSFORM_NEAREST;
-    if (!PyArg_ParseTuple(args, "(ii)|i", &xsize, &ysize, &filter))
-        return NULL;
-
+    float roi[4] = {0, 0, 0, 0};
+    
     imIn = self->image;
+    roi[2] = imIn->xsize;
+    roi[3] = imIn->ysize;
+    
+    if (!PyArg_ParseTuple(args, "(ii)|i(ffff)", &xsize, &ysize, &filter,
+                          &roi[0], &roi[1], &roi[2], &roi[3]))
+        return NULL;
 
     if (xsize < 1 || ysize < 1) {
         return ImagingError_ValueError("height and width must be > 0");
     }
 
+    if (roi[0] < 0 || roi[1] < 0) {
+        return ImagingError_ValueError("region of interest offset can't be negative");
+    }
+
+    if (roi[2] > imIn->xsize || roi[3] > imIn->ysize) {
+        return ImagingError_ValueError("region of interest can't exceed original image size");
+    }
+
+    if (roi[2] - roi[0] <= 0 || roi[3] - roi[1] <= 0) {
+        return ImagingError_ValueError("region of interest can't be empty");
+    }
+
     if (imIn->xsize == xsize && imIn->ysize == ysize) {
         imOut = ImagingCopy(imIn);
     }