EPUB Output: Add a warning about images in the CMYK colorspace

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

@@ -190,7 +190,7 @@ class EPUBOutput(OutputFormatPlugin):
         self.workaround_webkit_quirks()
         self.upshift_markup()
         from calibre.ebooks.oeb.transforms.rescale import RescaleImages
-        RescaleImages()(oeb, opts)
+        RescaleImages(check_colorspaces=True)(oeb, opts)
 
         from calibre.ebooks.oeb.transforms.split import Split
         split = Split(not self.opts.dont_split_on_page_breaks,

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

@@ -9,8 +9,12 @@ __docformat__ = 'restructuredtext en'
 from calibre import fit_image
 
 class RescaleImages(object):
+
     'Rescale all images to fit inside given screen size'
 
+    def __init__(self, check_colorspaces=False):
+        self.check_colorspaces = check_colorspaces
+
     def __call__(self, oeb, opts):
         self.oeb, self.opts, self.log = oeb, opts, oeb.log
         from calibre.gui2 import is_ok_to_use_qt
@@ -31,7 +35,8 @@ class RescaleImages(object):
         for item in self.oeb.manifest:
             if item.media_type.startswith('image'):
                 ext = item.media_type.split('/')[-1].upper()
-                if ext == 'JPG': ext = 'JPEG'
+                if ext == 'JPG':
+                    ext = 'JPEG'
                 if ext not in ('PNG', 'JPEG', 'GIF'):
                     ext = 'JPEG'
 
@@ -46,6 +51,16 @@ class RescaleImages(object):
                     continue
                 width, height = img.size
 
+                try:
+                    if self.check_colorspaces and img.colorspace == 'CMYKColorspace':
+                        # We cannot do an automatic conversion of CMYK to RGB as
+                        # ImageMagick inverts colors if you just set the colorspace
+                        # to rgb. See for example: https://bugs.launchpad.net/bugs/1246710
+                        self.log.warn(
+                            'The image %s is in the CMYK colorspace, you should convert'
+                            ' it to sRGB as Adobe Digital Editions cannot render CMYK' % item.href)
+                except Exception:
+                    pass
 
                 scaled, new_width, new_height = fit_image(width, height,
                         page_width, page_height)

src/calibre/utils/magick/__init__.py

@@ -20,6 +20,9 @@ _gravity_map = dict([(getattr(_magick, x), x) for x in dir(_magick) if
 _type_map = dict([(getattr(_magick, x), x) for x in dir(_magick) if
     x.endswith('Type')])
 
+_colorspace_map = dict([(getattr(_magick, x), x) for x in dir(_magick) if
+    x.endswith('Colorspace')])
+
 # Font metrics {{{
 class Rect(object):
 
@@ -165,6 +168,15 @@ class Image(_magick.Image):  # {{{
             self.type_ = val
         return property(fget=fget, fset=fset, doc=_magick.Image.type_.__doc__)
 
+    @dynamic_property
+    def colorspace(self):
+        def fget(self):
+            return _colorspace_map[self.colorspace_]
+        def fset(self, val):
+            val = getattr(_magick, str(val))
+            self.colorspace_ = val
+        return property(fget=fget, fset=fset, doc=_magick.Image.type_.__doc__)
+
     @dynamic_property
     def size(self):
         def fget(self):

src/calibre/utils/magick/magick.c

@@ -1252,6 +1252,41 @@ magick_Image_set_opacity(magick_Image *self, PyObject *args) {
 }
 // }}}
 
+// Image.colorspace {{{
+static PyObject *
+magick_Image_colorspace_getter(magick_Image *self, void *closure) {
+    NULL_CHECK(NULL)
+
+    return Py_BuildValue("i", MagickGetImageColorspace(self->wand));
+}
+
+static int
+magick_Image_colorspace_setter(magick_Image *self, PyObject *val, void *closure) {
+    int cs = RGBColorspace;
+
+    NULL_CHECK(-1)
+
+    if (val == NULL) {
+        PyErr_SetString(PyExc_TypeError, "Cannot delete image colorspace");
+        return -1;
+    }
+
+    if (!PyInt_Check(val)) {
+        PyErr_SetString(PyExc_TypeError, "Colorspace must be an integer");
+        return -1;
+    }
+
+    cs = (int)PyInt_AS_LONG(val);
+    if (!MagickSetImageColorspace(self->wand, cs)) {
+        PyErr_Format(PyExc_ValueError, "Could not set image colorspace to %d", cs);
+        return -1;
+    }
+
+    return 0;
+}
+
+// }}}
+
 // Image attr list {{{
 static PyMethodDef magick_Image_methods[] = {
     {"destroy", (PyCFunction)magick_Image_destroy, METH_VARARGS,
@@ -1395,6 +1430,10 @@ static PyGetSetDef  magick_Image_getsetters[] = {
      (char *)"the image depth.",
      NULL},
 
+    {(char *)"colorspace_",
+     (getter)magick_Image_colorspace_getter, (setter)magick_Image_colorspace_setter,
+     (char *)"the image colorspace.",
+     NULL},
 
     {NULL}  /* Sentinel */
 };