# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1444686588 -7200
# Node ID 363ec82436bd099f818227efc9c19e3533c1f978
# Parent  0d27eee1a2bba27589f4d4cc0901ac7626987328
Separated scaling and width-stretching operations.

diff -r 0d27eee1a2bb -r 363ec82436bd optimiser.py
--- a/optimiser.py	Mon Oct 12 20:45:09 2015 +0200
+++ b/optimiser.py	Mon Oct 12 23:49:48 2015 +0200
@@ -54,7 +54,7 @@
         y += 1
     im.save("rgb%02d%02d%02d.png" % rgb)
 
-def rotate_and_scale(exif, im, width, height, rotate):
+def rotate_and_scale(exif, im, width, height, rotate, scale_factor):
 
     """
     Using the given 'exif' information, rotate and scale image 'im' given the
@@ -68,14 +68,19 @@
 
     w, h = im.size
 
-    width_scale_factor = float(width) / w
+    # Get the relationship between the base width and the image width.
+
+    width_scale_factor = (width / scale_factor) / w
     height_scale_factor = float(height) / h
-    scale_factor = min(width_scale_factor, height_scale_factor)
+    min_scale_factor = min(width_scale_factor, height_scale_factor)
 
-    if scale_factor < 1:
-        width = int(scale_factor * w)
-        height = int(scale_factor * h)
+    if min_scale_factor < 1:
+        width = int(min_scale_factor * w * scale_factor)
+        height = int(min_scale_factor * h)
         return im.resize((width, height))
+    elif scale_factor != 1:
+        width = int(w * scale_factor)
+        return im.resize((width, h))
     else:
         return im
 
@@ -162,10 +167,9 @@
     number_of_colours = get_parameter(options, "-C", int, 4, 4)
     preserve_aspect_ratio = "-A" in options
 
-    # Determine whether the height will need adjusting before conversion.
+    # Determine any differing horizontal scale factor.
 
     scale_factor = float(width) / base_width
-    height = int(base_height * scale_factor)
 
     # Preprocessing options that employ parameters.
 
@@ -192,15 +196,9 @@
     if make_image or preview:
         exif = EXIF.process_file(open(input_filename))
         im = PIL.Image.open(input_filename).convert("RGB")
-        im = rotate_and_scale(exif, im, width, height, rotate)
+        im = rotate_and_scale(exif, im, width, height, rotate, scale_factor)
         image_width, image_height = im.size
 
-        # Scale images to the appropriate height.
-
-        if scale_factor != 1:
-            im = im.resize((image_width, int(image_height / scale_factor)))
-            image_width, image_height = im.size
-
         process_image(im, saturate, desaturate, darken, brighten)
 
     # Generate a preview if requested.