Add functionality to the magick_draw module and add commented out code to use it to resize new cover when updating EPUB metadata

src/calibre/ebooks/metadata/epub.py

@@ -5,7 +5,7 @@ __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
 '''Read meta information from epub files'''
 
-import os, re, posixpath
+import os, re, posixpath, shutil
 from cStringIO import StringIO
 from contextlib import closing
 
@@ -13,7 +13,7 @@ from calibre.utils.zipfile import ZipFile, BadZipfile, safe_replace
 from calibre.ebooks.BeautifulSoup import BeautifulStoneSoup
 from calibre.ebooks.metadata import MetaInformation
 from calibre.ebooks.metadata.opf2 import OPF
-from calibre.ptempfile import TemporaryDirectory
+from calibre.ptempfile import TemporaryDirectory, PersistentTemporaryFile
 from calibre import CurrentDir
 
 class EPubException(Exception):
@@ -205,11 +205,19 @@ def set_metadata(stream, mi, apply_null=False, update_timestamp=False):
             cover_replacable = not reader.encryption_meta.is_encrypted(cpath) and \
                     os.path.splitext(cpath)[1].lower() in ('.png', '.jpg', '.jpeg')
             if cover_replacable:
-                from calibre.ptempfile import PersistentTemporaryFile
-                from calibre.utils.magick_draw import save_cover_data_to
+                from calibre.utils.magick_draw import save_cover_data_to, \
+                    identify
                 new_cover = PersistentTemporaryFile(suffix=os.path.splitext(cpath)[1])
+                resize_to = None
+                if False: # Resize new cover to same size as old cover
+                    shutil.copyfileobj(reader.open(cpath), new_cover)
                     new_cover.close()
-                save_cover_data_to(new_cdata, new_cover.name)
+                    width, height, fmt = identify(new_cover.name)
+                    resize_to = (width, height)
+                else:
+                    new_cover.close()
+                save_cover_data_to(new_cdata, new_cover.name,
+                        resize_to=resize_to)
                 replacements[cpath] = open(new_cover.name, 'rb')
         except:
             import traceback

src/calibre/utils/PythonMagickWand.py

@@ -2661,7 +2661,7 @@ else:
     MagickGetImageSignature = _magick.MagickGetImageSignature
 #   MagickGetImageFormat
 try:
-    _magick.MagickGetImageFormat.restype = ctypes.POINTER(ctypes.c_char)
+    _magick.MagickGetImageFormat.restype = ctypes.c_char_p
     _magick.MagickGetImageFormat.argtypes = (MagickWand,)
 except AttributeError,e:
     pass

src/calibre/utils/magick_draw.py

@@ -220,7 +220,7 @@ def create_cover_page(top_lines, logo_path, width=590, height=750,
         p.DestroyMagickWand(canvas)
     return ans
 
-def save_cover_data_to(data, path, bgcolor='white'):
+def save_cover_data_to(data, path, bgcolor='white', resize_to=None):
     '''
     Saves image in data to path, in the format specified by the path
     extension. Composes the image onto a blank canvas so as to
@@ -230,6 +230,8 @@ def save_cover_data_to(data, path, bgcolor='white'):
         f.write(data)
     with p.ImageMagick():
         img = load_image(path)
+        if resize_to is not None:
+            p.MagickResizeImage(img, resize_to[0], resize_to[1], p.CatromFilter, 1.0)
         canvas = create_canvas(p.MagickGetImageWidth(img),
                 p.MagickGetImageHeight(img), bgcolor)
         compose_image(canvas, img, 0, 0)
@@ -237,6 +239,22 @@ def save_cover_data_to(data, path, bgcolor='white'):
         p.DestroyMagickWand(img)
         p.DestroyMagickWand(canvas)
 
+def identify(path):
+    '''
+    Identify the image at path. Returns a 3-tuple
+    (width, height, format)
+    or raises an IOError.
+    '''
+    with p.ImageMagick():
+        img = load_image(path)
+        width = p.MagickGetImageWidth(img)
+        height = p.MagickGetImageHeight(img)
+        fmt = p.MagickGetImageFormat(img)
+        if not fmt:
+            fmt = ''
+        fmt = fmt.decode('utf-8', 'replace')
+    return (width, height, fmt)
+
 def test():
     import subprocess
     with TemporaryFile('.png') as f: