比cv :: putText()更好的向ca cv :: Mat添加文本的方法? [英] A better way to add text to ca cv::Mat than cv::putText()?

问题描述

我想在cv::Mat上放一些文字，但是cv::putText()对我来说不够灵活.

I want to put some text on a cv::Mat, but cv::putText() is not flexible enough for me.

我需要在运行时已知的几个像素位置上放置可变长度的标签，但是由于cv::putText()总是将输出的原点放在左侧，因此如果位置太远，我的文本也会消失在图像边界之外在最左边.

I need to put labels of variable length at several pixel positions which are known at runtime, but since cv::putText() places the origin of the output always on the left, my text disappears beyond the image borders, if the position is too far on the left.

我找不到cv::putText()的替代品.有吗?

I could not find alternatives to cv::putText(). Are there any?

只要知道输出文本的宽度和高度(以像素为单位)，我就可以自己调整位置.

It would suffice for me to know the width and height of the output text in pixels, so I could adjust the position myself.

一种更好的方法是，我可以将文本的原点指定在右侧，左侧或中间(垂直和水平).

Even better would be a method where I could specify the origin of my text to be at the right, left or middle (vertically and horizontally).

作为奖励，我想绘制带有轮廓的文本，例如具有黑色轮廓的白色字符，以便您可以在任何背景上阅读它们.

As a bonus I'd like to draw text with contours, e.g. white characters with black contours, so that you can read them on any background.

推荐答案

以下是将freetype与OpenCV一起使用的示例:

Here is the example of using freetype with OpenCV:

#include "opencv2/opencv.hpp"

#include "ft2build.h"
#include FT_FREETYPE_H
FT_Library  library;
FT_Face     face;      

using namespace cv;
using namespace std;
//-----------------------------------------------------------------------
void my_draw_bitmap(Mat& img,FT_Bitmap* bitmap,int x,int y, Scalar color)
{
    Scalar src_col,dst_col;
    for(int i=0;i<bitmap->rows;i++)
    {
        for(int j=0;j<bitmap->width;j++)
        {
            unsigned char val=bitmap->buffer[j+i*bitmap->pitch];
            float mix=(float)val/255.0;                              
            if(val!=0)
            {
                src_col=Scalar(img.at<Vec3b>(i+y,j+x));
                dst_col=mix*color+(1.0-mix)*src_col;
                img.at<Vec3b>(i+y,j+x)=Vec3b(dst_col[0],dst_col[1],dst_col[2]);
            }
        }      
    }
}
//-----------------------------------------------------------------------
float PrintString(Mat& img,std::wstring str,int x,int y,Scalar color)
{
    FT_Bool       use_kerning=0;
    FT_UInt       previous=0;
    use_kerning = FT_HAS_KERNING( face );
    float prev_yadv=0;
    float posx=0;
    float posy=0;
    float dx=0;
    for(int k=0;k<str.length();k++)
    {
        int glyph_index = FT_Get_Char_Index( face, str.c_str()[k] );
        FT_GlyphSlot  slot = face->glyph;  // a small shortcut 
        if(k>0){dx=slot->advance.x/64;  }       
        FT_Load_Glyph( face, glyph_index, FT_LOAD_DEFAULT );
        FT_Render_Glyph (slot,FT_RENDER_MODE_NORMAL);
        prev_yadv=slot->metrics.vertAdvance/64; 
        if ( use_kerning && previous && glyph_index )
        {
            FT_Vector  delta;
            FT_Get_Kerning( face, previous, glyph_index, FT_KERNING_DEFAULT, &delta );
            posx += (delta.x/64);
        }
        posx+=(dx);
        my_draw_bitmap(img,&slot->bitmap,posx+x+ slot->bitmap_left,y - slot->bitmap_top+posy,color);
        previous = glyph_index;
    }
    return prev_yadv;
}
//-----------------------------------------------------------------------
void PrintText(Mat& img,std::wstring str,int x,int y,Scalar color)
{
    float posy=0;
    for(int pos=str.find_first_of(L'\n');pos!=wstring::npos;pos=str.find_first_of(L'\n'))
    {
        std::wstring substr=str.substr(0,pos);
        str.erase(0,pos+1);
        posy+=PrintString(img,substr,x,y+posy, color);
    }
    PrintString(img,str,x,y+posy,color);
}
//-----------------------------------------------------------------------
int main(int argc, char* argv[])
{
    FT_Init_FreeType( &library );
    FT_New_Face( library,"arial.ttf",0,&face );
    FT_Set_Pixel_Sizes(face,24,0);
    FT_Select_Charmap(face, FT_ENCODING_UNICODE);
    Mat img=imread("D:/ImagesForTest/lena.jpg");

    std::wstring str= L"Мой дядя самых честных правил,\n\
Когда не в шутку занемог,\n\
Он уважать себя заставил \n\
И лучше выдумать не мог.\n\
Его пример другим наука;\n\
Но, боже мой, какая скука\n\
С больным сидеть и день и ночь,\n\
Не отходя ни шагу прочь!\n\
Какое низкое коварство\n\
Полу-живого забавлять,\n\
Ему подушки поправлять,\n\
Печально подносить лекарство,\n\
Вздыхать и думать про себя:\n\
Когда же чёрт возьмет тебя!\n";

    PrintText(img,str,100,50,Scalar(0,255,255));
    cv::imshow("win",img);
    cv::waitKey(0);
    return 0;
}

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