getTextSize函数

getTextSize函数的函数声明如下：

CV_EXPORTS_W Size getTextSize(const String& text, int fontFace,
                            double fontScale, int thickness,
                            CV_OUT int* baseLine);

getTextSize用于给出opencv绘制文字时，文字的绘制范围，会计算出包围这些文字的包围盒；
主要参数

例子

在一张800*600的图像上，绘制Funny text inside the box文本，绘制文本的包围边框，以及baseline下划线；

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);

imshow("Image", img);
waitKey(0);