Merge pull request #2776 from Kumataro:master_freetype2_doc

freetype2: Fix comments in freetype.hpp and README.md

* freetype2: Update README.md

* freetype2: Update freetype.hpp

* freetype2: remove new blank line

* Update README.md

- Remove dots from the Headers
- Align number of === / --- symbols on the next line

* freetype: remove comment for color.

modules/freetype/README.md

@@ -1,34 +1,34 @@
-FreeType Module
-===========
+FreeType2 Wrapper Module
+========================
 
-This FreeType module allows you to draw strings with outlines and bitmaps.
+This FreeType2 wrapper module allows to draw strings with outlines and bitmaps.
+
+Requested external libraries
+----------------------------
 
-Installation
------------
 harfbuzz is requested to convert UTF8 to gid(GlyphID).
+
 freetype library is requested to rasterize given gid.
 
-harfbuzz https://www.freedesktop.org/wiki/Software/HarfBuzz/
-freetype https://www.freetype.org/
+- harfbuzz https://www.freedesktop.org/wiki/Software/HarfBuzz/
+- freetype https://www.freetype.org/
 
 Usage
------------
-cv::freetype::FreeType2 ft2;
-ft2.loadFontData("your-font.ttf", 0);
-ft2.setSplitNumber( 4 ); // Bezier-line is splited by 4 segment.
-ft2.putText(src, .... )
+-----
+
+```
+cv::Ptr<cv::freetype::FreeType2> ft2;
+ft2 = cv::freetype::createFreeType2();
+ft2->loadFontData(ttf_pathname, 0);
+ft2->putText(mat, "hello world", cv::Point(20, 200),
+             30, CV_RGB(0, 0, 0), cv::FILLED, cv::LINE_AA, true);
+```
 
 Option
-------------
+------
 - 2nd argument of loadFontData is used if font file has many font data.
 - 3 drawing mode is available.
--- outline mode is used if lineWidth is larger than 0. (like original putText)
--- bitmap  mode is used if lineWidth is less than 0.
---- 1bit bitmap mode is used if lineStyle is 4 or 8.
---- gray bitmap mode is used if lineStyle is 16.
-
-Future work
-------------
-- test
--- CJK and ...
-- RTL,LTR,TTB,BTT...
+    - outline mode is used if lineWidth is larger than 0. (like original putText)
+    - bitmap  mode is used if lineWidth is less than 0.
+        - 1bit bitmap mode is used if lineStyle is 4 or 8.
+        - gray bitmap mode is used if lineStyle is 16.

modules/freetype/include/opencv2/freetype.hpp

@@ -99,7 +99,7 @@ If you want to draw small glyph, small is better.
 
 The function putText renders the specified text string in the image. Symbols that cannot be rendered using the specified font are replaced by "Tofu" or non-drawn.
 
-@param img Image.
+@param img Image. (Only 8UC3 image is supported.)
 @param text Text string to be drawn.
 @param org Bottom-left/Top-left corner of the text string in the image.
 @param fontHeight Drawing font size by pixel unit.