ImageMagick: When identifying an image don't read the whole image

src/calibre/utils/magick/draw.py

@@ -92,7 +92,10 @@ def identify_data(data):
     or raises an Exception if data is not an image.
     '''
     img = Image()
-    img.load(data)
+    if hasattr(img, 'identify'):
+        img.identify(data)
+    else:
+        img.load(data)
     width, height = img.size
     fmt = img.format
     return (width, height, fmt)

src/calibre/utils/magick/magick.c

@@ -456,6 +456,26 @@ magick_Image_load(magick_Image *self, PyObject *args, PyObject *kwargs) {
 
 // }}}
 
+// Image.identify {{{
+static PyObject *
+magick_Image_identify(magick_Image *self, PyObject *args, PyObject *kwargs) {
+    const char *data;
+	Py_ssize_t dlen;
+    MagickBooleanType res;
+    
+    NULL_CHECK(NULL)
+    if (!PyArg_ParseTuple(args, "s#", &data, &dlen)) return NULL;
+
+    res = MagickPingImageBlob(self->wand, data, dlen);
+
+    if (!res)
+        return magick_set_exception(self->wand);
+
+    Py_RETURN_NONE;
+}
+
+// }}}
+
 // Image.open {{{
 static PyObject *
 magick_Image_read(magick_Image *self, PyObject *args, PyObject *kwargs) {
@@ -993,6 +1013,10 @@ static PyMethodDef magick_Image_methods[] = {
     {"destroy", (PyCFunction)magick_Image_destroy, METH_VARARGS,
     "Destroy the underlying ImageMagick Wand. WARNING: After using this method, all methods on this object will raise an exception."},
 
+    {"identify", (PyCFunction)magick_Image_identify, METH_VARARGS,
+     "Identify an image from a byte buffer (string)"
+    },
+
     {"load", (PyCFunction)magick_Image_load, METH_VARARGS,
      "Load an image from a byte buffer (string)"
     },