Move optional resizing into own function

Author: juhasch

src/jupyter_contrib_nbextensions/nbconvert_support/pre_embedimages.py

@@ -33,13 +33,14 @@ class EmbedImagesPreprocessor(Preprocessor):
 
         $ jupyter nbconvert --to html --EmbedImagesPreprocessor.embed_images=True mynotebook.ipynb
 
-    Further options are
+    Further options are::
 
         EmbedImagesPreprocessor.embed_remote_images=True
 
     to additionally embeds all images referenced by an url
     (e.g. http://jupyter.org/assets/nav_logo.svg) instead of a local file name.
-    Also
+
+    Another configuration option is::
 
         EmbedImagesPreprocessor.resize=small
 
@@ -48,7 +49,8 @@ class EmbedImagesPreprocessor(Preprocessor):
     version. Works only for raster images (i.e. png, jpg).
     Valid resize settings are: small = 500px, mid = 1000px, large = 2000px
     for maximum size in length or width.  No upscaling of small images will
-    be performed.
+    be performed. The Python package `PIL` needs to be installed for this
+    option to work.
 
     Example::
 
@@ -62,13 +64,49 @@ class EmbedImagesPreprocessor(Preprocessor):
     embed_images = Bool(False, help="Embed images as attachment").tag(config=True)
     embed_remote_images = Bool(False, help="Embed images referenced by an url as attachment").tag(config=True)
     resize = Unicode('', help="Resize images to save space (reduce size)").tag(config=True)
+    imgsizes = {'small': 500, 'mid': 1000, 'large': 2000}
 
     def preprocess(self, nb, resources):
         """Skip preprocessor if not enabled"""
         if self.embed_images:
             nb, resources = super(EmbedImagesPreprocessor, self).preprocess(nb, resources)
         return nb, resources
 
+    def resize_image(self, imgname, imgformat, imgdata):
+        """Resize images if desired and PIL is installed
+
+        Parameters
+        ----------
+            imgname: str
+                Name of image
+            imgformat: str
+                Format of image (JPG or PNG)
+            imgdata:
+                Binary image data
+
+        """
+        if imgformat in ['png', 'jpg']:
+            from io import BytesIO
+            try:
+                from PIL import Image
+            except ImportError:
+                self.log.info("Pillow library not available to resize images")
+                return imgdata
+            # Only make images smaller when rescaling
+            im = Image.open(BytesIO(imgdata))
+            factor = self.imgsizes[self.resize] / max(im.size)
+            if factor < 1.0:
+                newsize = (int(im.size[0] * factor), int(im.size[1] * factor))
+                newim = im.resize(newsize)
+                fp = BytesIO()
+                # PIL requires JPEG instead of JPG
+                newim.save(fp, format=imgformat.replace('jpg', 'jpeg'))
+                imgdata = fp.getvalue()
+                fp.close()
+                self.log.debug("Resized %d x %d image %s to size %d x %d pixels" %
+                               (im.size[0], im.size[1], imgname, newsize[0], newsize[1]))
+        return imgdata
+
     def replfunc_md(self, match):
         """Read image and store as base64 encoded attachment"""
         url = match.group(2)
@@ -85,31 +123,10 @@ def replfunc_md(self, match):
             with open(filename, 'rb') as f:
                 data = f.read()
 
-        # resize settings: small -> 500px, mid -> 1000px, large -> 200px
-        imgsizes = {'small': 500, 'mid': 1000, 'large': 2000}
-        if self.resize in imgsizes.keys() and imgformat in ['png', 'jpg']:
-            from io import BytesIO
-            try:
-                from PIL import Image
-            except ImportError:
-                self.log.info("Pillow library not available to resize images")
-                Image = None
-            if Image:
-                # Only make images smaller when rescaling
-                im = Image.open(BytesIO(data))
-                factor = imgsizes[self.resize] / max(im.size)
-                if factor < 1.0:
-                    newsize = (int(im.size[0] * factor), int(im.size[1] * factor))
-                    newim = im.resize(newsize)
-                    fp = BytesIO()
-                    # PIL requires JPEG instead of JPG
-                    newim.save(fp, format=imgformat.replace('jpg', 'jpeg'))
-                    data = fp.getvalue()
-                    fp.close()
-                    self.log.debug("Resized %d x %d image %s to size %d x %d pixels" %
-                                   (im.size[0], im.size[1], url, newsize[0], newsize[1]))
-
-        self.log.debug("embedding url: %s, format: %s" % (url, imgformat))
+        if self.resize in self.imgsizes.keys():
+            data = self.resize_image(url, imgformat, data)
+
+        self.log.debug("Embedding url: %s, format: %s" % (url, imgformat))
         b64_data = base64.b64encode(data).decode("utf-8")
         self.attachments[url] = {'image/' + imgformat: b64_data}