EPUB Output: Do not shrink images to fit the screen size by default.

This matches behavior of converting to other formats. A new option has
been added to the EPUB Output section to control the maximum size of
images.

src/calibre/ebooks/conversion/config.py

@@ -278,7 +278,7 @@ OPTIONS = {
         'epub': (
             'dont_split_on_page_breaks', 'flow_size', 'no_default_epub_cover',
             'no_svg_cover', 'epub_inline_toc', 'epub_toc_at_end', 'toc_title',
-            'preserve_cover_aspect_ratio', 'epub_flatten', 'epub_version'),
+            'preserve_cover_aspect_ratio', 'epub_flatten', 'epub_version', 'epub_max_image_size',),
 
         'fb2': ('sectionize', 'fb2_genre'),
 

src/calibre/ebooks/conversion/plugins/epub_output.py

@@ -124,6 +124,17 @@ class EPUBOutput(OutputFormatPlugin):
                 ' actually need it.')
         ),
 
+        OptionRecommendation(name='epub_max_image_size', recommended_value='none',
+            help=_('The maximum image size (width x height). A value of {0} means use the screen size from the output'
+                   ' profile. A value of {1} means no maximum size is specified. For example, a value of {2}'
+                   ' will cause all images to be resized so that their width is no more than {3} pixels and'
+                   ' their height is no more than {4} pixels. Note that this only affects the size of the actual'
+                   ' image files themselves. Any given image may be rendered at a different size depending on the styling'
+                   ' applied to it in the document.'
+                   ).format('none', 'profile', '100x200', 100, 200)
+        ),
+
+
         }
 
     recommendations = {('pretty_print', True, OptionRecommendation.HIGH)}
@@ -196,8 +207,9 @@ class EPUBOutput(OutputFormatPlugin):
         self.workaround_ade_quirks()
         self.workaround_webkit_quirks()
         self.upshift_markup()
+
         from calibre.ebooks.oeb.transforms.rescale import RescaleImages
-        RescaleImages(check_colorspaces=True)(oeb, opts)
+        RescaleImages(check_colorspaces=True)(oeb, opts, max_size=self.opts.epub_max_image_size)
 
         from calibre.ebooks.oeb.transforms.split import Split
         split = Split(not self.opts.dont_split_on_page_breaks,
@@ -385,7 +397,6 @@ class EPUBOutput(OutputFormatPlugin):
         from calibre.ebooks.oeb.base import XPath, XHTML, barename, urlunquote
 
         stylesheet = self.oeb.manifest.main_stylesheet
-
         # ADE cries big wet tears when it encounters an invalid fragment
         # identifier in the NCX toc.
         frag_pat = re.compile(r'[-A-Za-z0-9_:.]+$')

src/calibre/ebooks/conversion/plumber.py

@@ -140,7 +140,7 @@ OptionRecommendation(name='output_profile',
             choices=[x.short_name for x in output_profiles()],
             help=_('Specify the output profile. The output profile '
                    'tells the conversion system how to optimize the '
-                   'created document for the specified device (such as by resizing images for the device screen size). In some cases, '
+                   'created document for the specified device. In some cases, '
                    'an output profile can be used to optimize the output for a particular device, but this is rarely necessary. '
                    'Choices are:') + ', '.join([
                        x.short_name for x in output_profiles()])

src/calibre/ebooks/oeb/transforms/rescale.py

@@ -15,11 +15,11 @@ class RescaleImages:
     def __init__(self, check_colorspaces=False):
         self.check_colorspaces = check_colorspaces
 
-    def __call__(self, oeb, opts):
+    def __call__(self, oeb, opts, max_size: str = 'profile'):
         self.oeb, self.opts, self.log = oeb, opts, oeb.log
-        self.rescale()
+        self.rescale(max_size)
 
-    def rescale(self):
+    def rescale(self, max_size: str = 'profile'):
         from PIL import Image
         from io import BytesIO
 
@@ -32,6 +32,23 @@ class RescaleImages:
             page_width -= (self.opts.margin_left + self.opts.margin_right) * self.opts.dest.dpi/72
             page_height -= (self.opts.margin_top + self.opts.margin_bottom) * self.opts.dest.dpi/72
 
+        no_scale_size = 99999999999
+        if max_size == 'none':
+            page_width = page_height = no_scale_size
+        elif max_size != 'profile':
+            w, __, h = max_size.strip().lower().partition('x')
+            try:
+                page_width = int(w.strip())
+            except Exception:
+                page_width = no_scale_size
+            if page_width <= 0:
+                page_width = no_scale_size
+            try:
+                page_height = int(h.strip())
+            except Exception:
+                page_height = no_scale_size
+            if page_height <= 0:
+                page_height = no_scale_size
         for item in self.oeb.manifest:
             if item.media_type.startswith('image'):
                 ext = item.media_type.split('/')[-1].upper()

src/calibre/gui2/convert/epub_output.ui

@@ -14,10 +14,27 @@
    <string>Form</string>
   </property>
   <layout class="QGridLayout" name="gridLayout">
-   <item row="2" column="1">
+   <item row="7" column="0">
-    <widget class="QCheckBox" name="opt_preserve_cover_aspect_ratio">
+    <widget class="QLabel" name="label_3">
      <property name="text">
-      <string>Preserve cover &amp;aspect ratio</string>
+      <string>EP&amp;UB version:</string>
+     </property>
+     <property name="buddy">
+      <cstring>opt_epub_version</cstring>
+     </property>
+    </widget>
+   </item>
+   <item row="1" column="0">
+    <widget class="QCheckBox" name="opt_no_default_epub_cover">
+     <property name="text">
+      <string>No default &amp;cover</string>
+     </property>
+    </widget>
+   </item>
+   <item row="3" column="0">
+    <widget class="QCheckBox" name="opt_epub_inline_toc">
+     <property name="text">
+      <string>Insert inline &amp;Table of Contents</string>
      </property>
     </widget>
    </item>
@@ -31,6 +48,46 @@
      </property>
     </widget>
    </item>
+   <item row="8" column="0">
+    <spacer name="verticalSpacer">
+     <property name="orientation">
+      <enum>Qt::Vertical</enum>
+     </property>
+     <property name="sizeHint" stdset="0">
+      <size>
+       <width>20</width>
+       <height>262</height>
+      </size>
+     </property>
+    </spacer>
+   </item>
+   <item row="2" column="0">
+    <widget class="QCheckBox" name="opt_no_svg_cover">
+     <property name="text">
+      <string>No &amp;SVG cover</string>
+     </property>
+    </widget>
+   </item>
+   <item row="7" column="1">
+    <widget class="QComboBox" name="opt_epub_version"/>
+   </item>
+   <item row="1" column="1">
+    <widget class="QCheckBox" name="opt_epub_flatten">
+     <property name="text">
+      <string>&amp;Flatten EPUB file structure</string>
+     </property>
+    </widget>
+   </item>
+   <item row="4" column="0">
+    <widget class="QLabel" name="label_2">
+     <property name="text">
+      <string>&amp;Title for inserted ToC:</string>
+     </property>
+     <property name="buddy">
+      <cstring>opt_toc_title</cstring>
+     </property>
+    </widget>
+   </item>
    <item row="5" column="1">
     <widget class="QSpinBox" name="opt_flow_size">
      <property name="specialValueText">
@@ -50,47 +107,6 @@
      </property>
     </widget>
    </item>
-   <item row="7" column="0">
-    <spacer name="verticalSpacer">
-     <property name="orientation">
-      <enum>Qt::Vertical</enum>
-     </property>
-     <property name="sizeHint" stdset="0">
-      <size>
-       <width>20</width>
-       <height>262</height>
-      </size>
-     </property>
-    </spacer>
-   </item>
-   <item row="1" column="0">
-    <widget class="QCheckBox" name="opt_no_default_epub_cover">
-     <property name="text">
-      <string>No default &amp;cover</string>
-     </property>
-    </widget>
-   </item>
-   <item row="2" column="0">
-    <widget class="QCheckBox" name="opt_no_svg_cover">
-     <property name="text">
-      <string>No &amp;SVG cover</string>
-     </property>
-    </widget>
-   </item>
-   <item row="3" column="0">
-    <widget class="QCheckBox" name="opt_epub_inline_toc">
-     <property name="text">
-      <string>Insert inline &amp;Table of Contents</string>
-     </property>
-    </widget>
-   </item>
-   <item row="0" column="0" colspan="2">
-    <widget class="QCheckBox" name="opt_dont_split_on_page_breaks">
-     <property name="text">
-      <string>Do not &amp;split on page breaks</string>
-     </property>
-    </widget>
-   </item>
    <item row="3" column="1">
     <widget class="QCheckBox" name="opt_epub_toc_at_end">
      <property name="text">
@@ -98,20 +114,17 @@
      </property>
     </widget>
    </item>
-   <item row="1" column="1">
+   <item row="2" column="1">
-    <widget class="QCheckBox" name="opt_epub_flatten">
+    <widget class="QCheckBox" name="opt_preserve_cover_aspect_ratio">
      <property name="text">
-      <string>&amp;Flatten EPUB file structure</string>
+      <string>Preserve cover &amp;aspect ratio</string>
      </property>
     </widget>
    </item>
-   <item row="4" column="0">
+   <item row="0" column="0" colspan="2">
-    <widget class="QLabel" name="label_2">
+    <widget class="QCheckBox" name="opt_dont_split_on_page_breaks">
      <property name="text">
-      <string>&amp;Title for inserted ToC:</string>
+      <string>Do not &amp;split on page breaks</string>
-     </property>
-     <property name="buddy">
-      <cstring>opt_toc_title</cstring>
      </property>
     </widget>
    </item>
@@ -123,17 +136,17 @@
     </widget>
    </item>
    <item row="6" column="0">
-    <widget class="QLabel" name="label_3">
+    <widget class="QLabel" name="label_4">
      <property name="text">
-      <string>EP&amp;UB version:</string>
+      <string>Shrink &amp;images larger than:</string>
      </property>
      <property name="buddy">
-      <cstring>opt_epub_version</cstring>
+      <cstring>opt_epub_max_image_size</cstring>
      </property>
     </widget>
    </item>
    <item row="6" column="1">
-    <widget class="QComboBox" name="opt_epub_version"/>
+    <widget class="QLineEdit" name="opt_epub_max_image_size"/>
    </item>
   </layout>
  </widget>

src/pyj/book_list/conversion_widgets.pyj

@@ -540,6 +540,7 @@ def epub_output(container):
     g.appendChild(checkbox('epub_toc_at_end', _('Put inserted Table of Contents at the &end of the book')))
     g.appendChild(lineedit('toc_title', _('&Title for inserted ToC:')))
     g.appendChild(int_spin('flow_size', _('Split files &larger than:'), unit='KB', max=1000000, step=20))
+    g.appendChild(lineedit('epub_max_image_size', _('Shrink &images larger than:')))
     g.appendChild(choices('epub_version', _('EP&UB version:'), ui_data.versions))
 # }}}