Added contain method

Tests/test_imageops.py

@@ -37,6 +37,9 @@ def test_sanity():
     ImageOps.pad(hopper("L"), (128, 128))
     ImageOps.pad(hopper("RGB"), (128, 128))
 
+    ImageOps.contain(hopper("L"), (128, 128))
+    ImageOps.contain(hopper("RGB"), (128, 128))
+
     ImageOps.crop(hopper("L"), 1)
     ImageOps.crop(hopper("RGB"), 1)
 
@@ -99,6 +102,21 @@ def test_fit_same_ratio():
         assert new_im.size == (1000, 755)
 
 
+def test_contain():
+    # Same ratio
+    im = hopper()
+    new_size = (im.width * 2, im.height * 2)
+    new_im = ImageOps.contain(im, new_size)
+    assert new_im.size == new_size
+
+    for new_size in [
+        (im.width * 4, im.height * 2),
+        (im.width * 2, im.height * 4),
+    ]:
+        new_im = ImageOps.contain(im, new_size)
+        assert new_im.size == (im.width * 2, im.height * 2)
+
+
 def test_pad():
     # Same ratio
     im = hopper()

src/PIL/ImageOps.py

@@ -236,6 +236,34 @@ def colorize(image, black, white, mid=None, blackpoint=0, whitepoint=255, midpoi
     return _lut(image, red + green + blue)
 
 
+def contain(image, size, method=Image.BICUBIC):
+    """
+    Returns a sized version of the image, expanded to fill the requested aspect ratio
+    and size.
+
+    :param image: The image to size and crop.
+    :param size: The requested output size in pixels, given as a
+                 (width, height) tuple.
+    :param method: What resampling method to use. Default is
+                   :py:attr:`PIL.Image.BICUBIC`. See :ref:`concept-filters`.
+    :return: An image.
+    """
+
+    im_ratio = image.width / image.height
+    dest_ratio = size[0] / size[1]
+
+    if im_ratio != dest_ratio:
+        if im_ratio > dest_ratio:
+            new_height = int(image.height / image.width * size[0])
+            if new_height != size[1]:
+                size = (size[0], new_height)
+        else:
+            new_width = int(image.width / image.height * size[1])
+            if new_width != size[0]:
+                size = (new_width, size[1])
+    return image.resize(size, resample=method)
+
+
 def pad(image, size, method=Image.BICUBIC, color=None, centering=(0.5, 0.5)):
     """
     Returns a sized and padded version of the image, expanded to fill the
@@ -257,27 +285,17 @@ def pad(image, size, method=Image.BICUBIC, color=None, centering=(0.5, 0.5)):
     :return: An image.
     """
 
-    im_ratio = image.width / image.height
-    dest_ratio = size[0] / size[1]
-
-    if im_ratio == dest_ratio:
-        out = image.resize(size, resample=method)
+    resized = contain(image, size, method)
+    if resized.size == size:
+        out = resized
     else:
         out = Image.new(image.mode, size, color)
-        if im_ratio > dest_ratio:
-            new_height = int(image.height / image.width * size[0])
-            if new_height != size[1]:
-                image = image.resize((size[0], new_height), resample=method)
-
-            y = int((size[1] - new_height) * max(0, min(centering[1], 1)))
-            out.paste(image, (0, y))
+        if resized.width != size[0]:
+            x = int((size[0] - resized.width) * max(0, min(centering[0], 1)))
+            out.paste(resized, (x, 0))
         else:
-            new_width = int(image.width / image.height * size[1])
-            if new_width != size[0]:
-                image = image.resize((new_width, size[1]), resample=method)
-
-            x = int((size[0] - new_width) * max(0, min(centering[0], 1)))
-            out.paste(image, (x, 0))
+            y = int((size[1] - resized.height) * max(0, min(centering[1], 1)))
+            out.paste(resized, (0, y))
     return out