[Docs] Fix some bugs in readthedocs pdf build. (#383)

* Add escape symbols for underscores in formulas.

* Support Chinese characters in pdf output.

docs/conf.py

@@ -74,6 +74,26 @@ html_theme = 'sphinx_rtd_theme'
 
 master_doc = 'index'
 
+latex_elements = {
+# Additional stuff for the LaTeX preamble.
+#'preamble': '',
+'preamble': r'''
+\hypersetup{unicode=true}
+\usepackage{CJKutf8}
+\DeclareUnicodeCharacter{00A0}{\nobreakspace}
+\DeclareUnicodeCharacter{2203}{\ensuremath{\exists}}
+\DeclareUnicodeCharacter{2200}{\ensuremath{\forall}}
+\DeclareUnicodeCharacter{2286}{\ensuremath{\subseteq}}
+\DeclareUnicodeCharacter{2713}{x}
+\DeclareUnicodeCharacter{27FA}{\ensuremath{\Longleftrightarrow}}
+\DeclareUnicodeCharacter{221A}{\ensuremath{\sqrt{}}}
+\DeclareUnicodeCharacter{221B}{\ensuremath{\sqrt[3]{}}}
+\DeclareUnicodeCharacter{2295}{\ensuremath{\oplus}}
+\DeclareUnicodeCharacter{2297}{\ensuremath{\otimes}}
+\begin{CJK}{UTF8}{gbsn}
+\AtEndDocument{\end{CJK}}
+''',
+}
 
 def builder_inited_handler(app):
     subprocess.run(['./stat.py'])

mmcls/datasets/pipelines/auto_augment.py

@@ -93,8 +93,8 @@ class RandAugment(object):
         When magnitude_std=0, we calculate the magnitude as follows:
 
         .. math::
-            \text{magnitude} = \frac{\text{magnitude_level}}
+            \text{magnitude} = \frac{\text{magnitude\_level}}
-            {\text{total_level}} \times (\text{val2} - \text{val1})
+            {\text{total\_level}} \times (\text{val2} - \text{val1})
             + \text{val1}
     """
 

mmcls/datasets/pipelines/transforms.py

@@ -721,8 +721,8 @@ class CenterCrop(object):
           to perform the center crop with the ``crop_size_`` as:
 
         .. math::
-            \text{crop_size_} = \frac{\text{crop_size}}{\text{crop_size} +
+            \text{crop\_size\_} = \frac{\text{crop\_size}}{\text{crop\_size} +
-            \text{crop_padding}} \times \text{short_edge}
+            \text{crop\_padding}} \times \text{short\_edge}
 
         And then the pipeline resizes the img to the input crop size.
     """