cv::freetype::FreeType2 Class Reference

#include <opencv2/freetype.hpp>

Collaboration diagram for cv::freetype::FreeType2:

Public Member Functions
virtual Size	getTextSize (const String &text, int fontHeight, int thickness, int *baseLine)=0
	Calculates the width and height of a text string.
virtual void	loadFontData (char *pBuf, size_t bufSize, int idx)=0
	Load font data.
virtual void	loadFontData (String fontFileName, int idx)=0
	Load font data.
virtual void	putText (InputOutputArray img, const String &text, Point org, int fontHeight, Scalar color, int thickness, int line_type, bool bottomLeftOrigin)=0
	Draws a text string.
virtual void	setSplitNumber (int num)=0
	Set Split Number from Bezier-curve to line.
Public Member Functions inherited from cv::Algorithm
	Algorithm ()
virtual	~Algorithm ()
virtual void	clear ()
	Clears the algorithm state.
virtual bool	empty () const
	Returns true if the Algorithm is empty (e.g. in the very beginning or after unsuccessful read.
virtual String	getDefaultName () const
virtual void	read (const FileNode &fn)
	Reads algorithm parameters from a file storage.
virtual void	save (const String &filename) const
void	write (const Ptr< FileStorage > &fs, const String &name=String()) const
virtual void	write (FileStorage &fs) const
	Stores algorithm parameters in a file storage.
void	write (FileStorage &fs, const String &name) const

Additional Inherited Members
Static Public Member Functions inherited from cv::Algorithm
template<typename _Tp >
static Ptr< _Tp >	load (const String &filename, const String &objname=String())
	Loads algorithm from the file.
template<typename _Tp >
static Ptr< _Tp >	loadFromString (const String &strModel, const String &objname=String())
	Loads algorithm from a String.
template<typename _Tp >
static Ptr< _Tp >	read (const FileNode &fn)
	Reads algorithm from the file node.
Protected Member Functions inherited from cv::Algorithm
void	writeFormat (FileStorage &fs) const

Member Function Documentation

getTextSize()

virtual Size cv::freetype::FreeType2::getTextSize ( const String & text, int fontHeight, int thickness, int * baseLine )

pure virtual

Calculates the width and height of a text string.

The function getTextSize calculates and returns the approximate size of a box that contains the specified text. That is, the following code renders some text, the tight box surrounding it, and the baseline: :

String text = "Funny text inside the box";
int fontHeight = 60;
int thickness = -1;
int linestyle = LINE_8;
 
Mat img(600, 800, CV_8UC3, Scalar::all(0));
 
int baseline=0;
 
cv::Ptr<cv::freetype::FreeType2> ft2;
ft2 = cv::freetype::createFreeType2();
ft2->loadFontData( "./mplus-1p-regular.ttf", 0 );
 
Size textSize = ft2->getTextSize(text,
                                 fontHeight,
                                 thickness,
                                 &baseline);
 
if(thickness > 0){
    baseline += thickness;
}
 
// center the text
Point textOrg((img.cols - textSize.width) / 2,
              (img.rows + textSize.height) / 2);
 
// draw the box
rectangle(img, textOrg + Point(0, baseline),
          textOrg + Point(textSize.width, -textSize.height),
          Scalar(0,255,0),1,8);
 
// ... and the baseline first
line(img, textOrg + Point(0, thickness),
     textOrg + Point(textSize.width, thickness),
     Scalar(0, 0, 255),1,8);
 
// then put the text itself
ft2->putText(img, text, textOrg, fontHeight,
             Scalar::all(255), thickness, linestyle, true );

Parameters

	text	Input text string.
	fontHeight	Drawing font size by pixel unit.
	thickness	Thickness of lines used to render the text. See putText for details.
[out]	baseLine	y-coordinate of the baseline relative to the bottom-most text point.

Returns

The size of a box that contains the specified text.

See also

cv::putText

loadFontData() [1/2]

virtual void cv::freetype::FreeType2::loadFontData ( char * pBuf, size_t bufSize, int idx )

pure virtual

Load font data.

The function loadFontData loads font data from memory. The data is not copied, the user needs to make sure the data lives at least as long as FreeType2. After the FreeType2 object is destroyed, the buffer can be safely deallocated.

Parameters

pBuf	pointer to buffer containing font data
bufSize	size of buffer
idx	face_index to select a font faces in a single file.

loadFontData() [2/2]

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

pure virtual

Load font data.

The function loadFontData loads font data from file.

Parameters

fontFileName	FontFile Name
idx	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. (Only 8UC1/8UC3/8UC4 2D mat is supported.)
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

---

The documentation for this class was generated from the following file:

• opencv2/freetype.hpp