Drawing UTF-8 strings with freetype/harfbuzz

Classes
class	cv::freetype::FreeType2

Functions
Ptr< FreeType2 >	cv::freetype::createFreeType2 ()
	Create FreeType2 Instance. More...
virtual void	cv::freetype::FreeType2::loadFontData (String fontFileName, int id)=0
	Load font data. More...
virtual void	cv::freetype::FreeType2::putText (InputOutputArray img, const String &text, Point org, int fontHeight, Scalar color, int thickness, int line_type, bool bottomLeftOrigin)=0
	Draws a text string. More...
virtual void	cv::freetype::FreeType2::setSplitNumber (int num)=0
	Set Split Number from Bezier-curve to line. More...

Detailed Description

This modules is to draw UTF-8 strings with freetype/harfbuzz.

1. Install freetype2 and harfbuzz in your system.
2. Create FreeType2 instance with createFreeType2() function.
3. Load font file with loadFontData() function.
4. Draw text with putText() function.

• If thickness parameter is negative, drawing glyph is filled.
• If thickness parameter is positive, drawing glyph is outlined with thickness.
• If line_type parameter is 16(or CV_AA), drawing glyph is smooth.

Function Documentation

createFreeType2()

Ptr<FreeType2> cv::freetype::createFreeType2

(

)

Create FreeType2 Instance.

The function createFreeType2 create instance to draw UTF-8 strings.

loadFontData()

virtual void cv::freetype::FreeType2::loadFontData ( String  fontFileName, int  id  )

pure virtual

Load font data.

The function loadFontData loads font data.

Parameters

fontFileName	FontFile Name
id	face_index to select a font faces in a single file.

putText()

virtual void cv::freetype::FreeType2::putText ( InputOutputArray  img, const String &  text, Point  org, int  fontHeight, Scalar  color, int  thickness, int  line_type, bool  bottomLeftOrigin  )

pure virtual

Draws a text string.

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.

Parameters

img	Image.
text	Text string to be drawn.
org	Bottom-left/Top-left corner of the text string in the image.
fontHeight	Drawing font size by pixel unit.
color	Text color.
thickness	Thickness of the lines used to draw a text when negative, the glyph is filled. Otherwise, the glyph is drawn with this thickness.
line_type	Line type. See the line for details.
bottomLeftOrigin	When true, the image data origin is at the bottom-left corner. Otherwise, it is at the top-left corner.

setSplitNumber()

virtual void cv::freetype::FreeType2::setSplitNumber ( int  num )

pure virtual

Set Split Number from Bezier-curve to line.

The function setSplitNumber set the number of split points from bezier-curve to line. If you want to draw large glyph, large is better. If you want to draw small glyph, small is better.

Parameters

num	number of split points from bezier-curve to line