Opencv显示文字相关函数

Opencv中定义了一些用于显示文字相关的函数，将文字放于图像中。

文字结构有：CvFont

文字输出函数有：cvInitFont、getTextSize、putText

CvFont结构定义：

/** Font structure */

typedef struct CvFont

{

const char* nameFont; //Qt:nameFont

CvScalar color; //Qt:ColorFont -> cvScalar(blue_component, green_component, red_component[, alpha_component])

int font_face; //Qt: bool italic /** =CV_FONT_* */

const int* ascii; //!< font data and metrics

const int* greek;

const int* cyrillic;

float hscale, vscale;

float shear; //!< slope coefficient: 0 - normal, >0 - italic

int thickness; //!< Qt: weight /** letters thickness */

float dx; //!< horizontal interval between letters

int line_type; //!< Qt: PointSize

}

CvFont;

cvInitFont函数定义与描述：

/** @brief Initializes font structure (OpenCV 1.x API).

The function initializes the font structure that can be passed to text rendering functions.

@param font Pointer to the font structure initialized by the function

@param font_face Font name identifier. See cv::HersheyFonts and corresponding old CV_* identifiers.

@param hscale Horizontal scale. If equal to 1.0f , the characters have the original width

depending on the font type. If equal to 0.5f , the characters are of half the original width.

@param vscale Vertical scale. If equal to 1.0f , the characters have the original height depending

on the font type. If equal to 0.5f , the characters are of half the original height.

@param shear Approximate tangent of the character slope relative to the vertical line. A zero

value means a non-italic font, 1.0f means about a 45 degree slope, etc.

@param thickness Thickness of the text strokes

@param line_type Type of the strokes, see line description

@sa cvPutText

CVAPI(void) cvInitFont( CvFont* font, int font_face,

double hscale, double vscale,

double shear CV_DEFAULT(0),

int thickness CV_DEFAULT(1),

int line_type CV_DEFAULT(8));

CV_INLINE CvFont cvFont( double scale, int thickness CV_DEFAULT(1) )

{

CvFont font;

cvInitFont( &font, CV_FONT_HERSHEY_PLAIN, scale, scale, 0, thickness, CV_AA );

return font;

}

getTextSize函数定义与描述：

/** @brief Calculates the width and height of a text string.

The function cv::getTextSize calculates and returns the 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: :

@code

String text = "Funny text inside the box";

int fontFace = FONT_HERSHEY_SCRIPT_SIMPLEX;

double fontScale = 2;

int thickness = 3;

Mat img(600, 800, CV_8UC3, Scalar::all(0));

int baseline=0;

Size textSize = getTextSize(text, fontFace,

fontScale, thickness, &baseline);

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(0,0,255));

// ... and the baseline first

line(img, textOrg + Point(0, thickness),

textOrg + Point(textSize.width, thickness),

Scalar(0, 0, 255));

// then put the text itself

putText(img, text, textOrg, fontFace, fontScale,

Scalar::all(255), thickness, 8);

@endcode

@param text Input text string.

@param fontFace Font to use, see #HersheyFonts.

@param fontScale Font scale factor that is multiplied by the font-specific base size.

@param thickness Thickness of lines used to render the text. See #putText for details.

@param[out] baseLine y-coordinate of the baseline relative to the bottom-most text

point.

@return The size of a box that contains the specified text.

@see putText

CV_EXPORTS_W Size getTextSize(const String& text, int fontFace,

double fontScale, int thickness,

CV_OUT int* baseLine);

getTextSize函数定义与描述：

/** @brief Draws a text string.

The function cv::putText renders the specified text string in the image. Symbols that cannot be rendered

using the specified font are replaced by question marks. See #getTextSize for a text rendering code

example.

@param img Image.

@param text Text string to be drawn.

@param org Bottom-left corner of the text string in the image.

@param fontFace Font type, see #HersheyFonts.

@param fontScale Font scale factor that is multiplied by the font-specific base size.

@param color Text color.

@param thickness Thickness of the lines used to draw a text.

@param lineType Line type. See #LineTypes

@param bottomLeftOrigin When true, the image data origin is at the bottom-left corner. Otherwise,

it is at the top-left corner.

CV_EXPORTS_W void putText( InputOutputArray img, const String& text, Point org,

int fontFace, double fontScale, Scalar color,

int thickness = 1, int lineType = LINE_8,

bool bottomLeftOrigin = false );

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