纯C++代码实现将像素矩阵保存为bmp图片

由于工作需要，时常需要将像素矩阵保存图片显示观看。为此，特地总结了三种使用纯C++代码生成bmp图片的方法。分别是使用自定义数据、从外界导入的txt和csv以及从图片中导入的数据。

1. 1.使用自定义数据保存为bmp图片

   自定义数据可以是使用公式生成，或者是根据自己需求自己定义的数据，范围为0-255，分别对应从黑色到白色。代码生成过程如下：
   

   #pragma warning(disable:4996)
   #include<iostream>
   #include<string>
   using namespace std;
   
   //#define FrameSize 960*960  //视频帧大小
   int width = 120, height = 120;
   #define FrameNum 300       //yuv帧数
   static const double S_PI = 3.14159265358979323846;
   #define scos(x)         cos((double)(x))
   #define stan(x)         tan((double)(x))
   #define ssqrt(x)        sqrt((double)(x))
   #define ET_SIZE 300
   char errorText[ET_SIZE];
   
   void errorMsg(const char *msg) 
   {
       printf("error:%s
   ", msg);
   #ifdef _WIN32
       system("pause");
   #endif
       exit(-1);
   }
   
   void readSequence(unsigned char *frames)
   {
       //Test start    
       for (int y = 0; y < height; y++)
       {
           for (int x = 0; x < width; x++)
           {
               //使用公式生成像素数据
               float pu0 = (float)((2.0*(x + 0.5)) / width - 1.0);
               float pv0 = (float)((2.0*(y + 0.5)) / height - 1.0);
   
               double tu0 = stan(pu0*S_PI / 4.0);
               double tv0 = stan(pv0*S_PI / 4.0);
               double value= 1.0 / (scos(pu0*S_PI / 4.0)*scos(pu0*S_PI / 4.0)*scos(pv0*S_PI / 4.0)*scos(pv0*S_PI / 4.0) * (tu0*tu0 + tv0*tv0 + 1.0) * ssqrt(tu0*tu0 + tv0*tv0 + 1.0));
   
               //将值从(0，1)放大到(0，255)
               value= 255.0*value;
               //将值从(128，255)放大到(0，255),增加图像对比度
               frames[y*width + x] = 2.0*value- 255.0;
           }
       }
   }
   
   void write_bmpheader(unsigned char *bitmap, int offset, int bytes, int value) 
   {
       int i;
       for (i = 0; i < bytes; i++)
           bitmap[offset + i] = (value >> (i << 3)) & 0xFF;
   }
   
   unsigned char *convertToBmp(unsigned char *inputImg, int width, int height, int *ouputSize) 
   {
       /*create a bmp format file*/
       int bitmap_x = (int)ceil((double)width * 3 / 4) * 4;
       unsigned char *bitmap = (unsigned char*)malloc(sizeof(unsigned char)*height*bitmap_x + 54);
   
       bitmap[0] = 'B';
       bitmap[1] = 'M';
       write_bmpheader(bitmap, 2, 4, height*bitmap_x + 54); //whole file size
       write_bmpheader(bitmap, 0xA, 4, 54); //offset before bitmap raw data
       write_bmpheader(bitmap, 0xE, 4, 40); //length of bitmap info header
       write_bmpheader(bitmap, 0x12, 4, width); //width
       write_bmpheader(bitmap, 0x16, 4, height); //height
       write_bmpheader(bitmap, 0x1A, 2, 1);
       write_bmpheader(bitmap, 0x1C, 2, 24); //bit per pixel
       write_bmpheader(bitmap, 0x1E, 4, 0); //compression
       write_bmpheader(bitmap, 0x22, 4, height*bitmap_x); //size of bitmap raw data
   
       for (int i = 0x26; i < 0x36; i++)
           bitmap[i] = 0;
       int k = 54;
       for (int i = height - 1; i >= 0; i--) {
           int j;
           for (j = 0; j < width; j++) {
               int index = i*width + j;
               for (int l = 0; l < 3; l++)
                   bitmap[k++] = inputImg[index];
           }
           j *= 3;
           while (j < bitmap_x) {
               bitmap[k++] = 0;
               j++;
           }
       }
       *ouputSize = k;
       return bitmap;
   }
   
   void saveToBmp(unsigned char *inputImg, int width, int height, char *outputFileName) 
   {
       int size;
       unsigned char *bmp = convertToBmp(inputImg, width, height, &size);
       FILE *fp = fopen(outputFileName, "wb+");
       if (fp == NULL) {
           sprintf(errorText, "Could not open file: %s", outputFileName);
           errorMsg(errorText);
       }
       fwrite(bmp, 1, size, fp);
       fclose(fp);
       free(bmp);
   }
   int main() 
   {
       unsigned char *oriFrames;
       oriFrames = (unsigned char*)malloc(sizeof(unsigned char) * width * height);
       readSequence(oriFrames);
   
       char imgName[30];
       sprintf(imgName, "F:\pictures\Bitmap_Weight_Map_Convex2.bmp");
       //矩阵oriFrames[i]可以是任何你想保存为图片的像素矩阵，这里是yuv视频图像每一帧的像素数据
       saveToBmp(oriFrames, width, height, imgName);
       //system("pause");
   }

    

1. 2.从外界导入的txt和csv保存为bmp图片
   将数据导入txt中：

   #pragma warning(disable:4996)
   #include <stdio.h>
   #include <stdlib.h>
   int main()
   {
       //文件写操作txt
       FILE *fp;//文件指针    
       int i, d;     
       /*文件的打开*/
       fp = fopen("E:\VS_Test_Code\data.txt", "w");//fopen打开文件，这个文件可以是当前不存在的。“w”以写入的形式打开，“r”以读的形式打开    
       if (fp == NULL) //判断如果文件指针为空    
       {
           printf("File cannot open! ");
           exit(0);//在以0的形式退出，必须在文件开头有#include <stdlib.h>,stdlib 头文件即standard library标准库头文件    
       }
       //写入数据   
       for (i = 0; i < 10; i++)
       {
           scanf("%d", &d);//用户输入        
           fprintf(fp, "%d，", d);//写入指针fp，写入的东西就是刚才的用户输入的d,注意这里的fp和d没有引号    
       }
       //关闭文件    
       fclose(fp);
   }

   从txt中读取数据：

   #pragma warning(disable:4996)
   #include <stdio.h>
   #include <stdlib.h>
   int main()
   {
       //文件读操作txt
       FILE *fp;//文件指针    
       int i, d;     
       /*文件的打开*/
       fp = fopen("E:\VS_Test_Code\data.txt", "r");//fopen打开文件，这个文件可以是当前不存在的。“w”以写入的形式打开，“r”以读的形式打开    
       if (fp == NULL) //判断如果文件指针为空    
       {
           printf("File cannot open! ");
           exit(0);//在以0的形式退出，必须在文件开头有#include <stdlib.h>,stdlib 头文件即standard library标准库头文件    
       }
       int *array = (int*)malloc(sizeof(int) * 10);
       //读取数据   
       for (i = 0; i < 10; i++)
       {
           fscanf(fp, "%d，", &array[i]);//从文件输入        
           printf("%d ", array[i]);//写入指针fp，写入的东西就是刚才的用户输入的d,注意这里的fp和d没有引号    
       }
       printf("
   ");
       //关闭文件    
       fclose(fp);
       system("pause");//使窗口保持不关闭
   }

   将数据导入csv中：

   #pragma warning(disable:4996)
   #include <stdio.h>
   #include <stdlib.h>
   int main()
   {
       //文件写操作csv
       FILE *fp;//文件指针    
       int i, No;
       double salary;
       fp = fopen("E:\VS_Test_Code\data.csv", "w");//fopen打开文件，这个文件可以是当前不存在的。“w”以写入的形式打开，“r”以读的形式打开    
       if (fp == NULL) //判断如果文件指针为空    
       {
           printf("File cannot open! ");
           exit(0);//在以0的形式退出，必须在文件开头有#include <stdlib.h>,stdlib 头文件即standard library标准库头文件    
       }
       //写入数据   
       for (i = 0; i < 5; i++)
       {
           scanf("%d %lf", &No, &salary);//用户输入，double一定要用%lf        
           fprintf(fp, "%d %.2f
   ", No, salary);//写入指针fp，写入的东西就是刚才的用户输入的d,注意这里的fp和d没有引号    
       }
       //关闭文件    
       fclose(fp);
   }

   从csv中读取数据：

   #pragma warning(disable:4996)
   #include <stdio.h>
   #include <stdlib.h>
   int main()
   {
       //文件读操作csv
       FILE *fp;//文件指针    
       int i, No;
       double salary;
       fp = fopen("E:\VS_Test_Code\data.csv", "r");//fopen打开文件，这个文件可以是当前不存在的。“w”以写入的形式打开，“r”以读的形式打开    
       if (fp == NULL) //判断如果文件指针为空    
       {
           printf("File cannot open! ");
           exit(0);//在以0的形式退出，必须在文件开头有#include <stdlib.h>,stdlib 头文件即standard library标准库头文件    
       }
       //读取数据   
       for (i = 0; i < 5; i++)
       {
           fscanf(fp, "%d %lf", &No, &salary);//用户输入,double要用%lf        
           printf("%d	%.2f
   ", No, salary);//写入指针fp，写入的东西就是刚才的用户输入的d,注意这里的fp和d没有引号    
       }
       //关闭文件    
       fclose(fp);
       system("pause");
   }

   将txt中的数据保存为bmp图片

   #pragma warning(disable:4996)
   #include<iostream>
   #include<string>
   using namespace std;
   
   #define FrameSize 100*100  //视频帧大小
   #define FrameNum 10       //yuv帧数
   #define ET_SIZE 300
   char errorText[ET_SIZE];
   
   void errorMsg(const char *msg) {
   
       printf("error:%s
   ", msg);
   
   #ifdef _WIN32
   
       system("pause");
   
   #endif
   
       exit(-1);
   
   }
   
   void readSequence(char *fileName, unsigned char **frames)
   {
       FILE *fp = fopen(fileName, "rb");
       if (fp == NULL)
       {
           sprintf(errorText, "File %s doesn't exist
   ", fileName);
           errorMsg(errorText);
       }
   
       int uvSize = FrameSize / 2;            //H.264编解码获得的关键帧都是彩色序列，这里主要是提取亮度分量Y。
       unsigned char *buf = (unsigned char *)malloc(sizeof(unsigned char) * uvSize);
       for (int i = 0; i < FrameNum; i++) {
           //read y
           if (fread(frames[i], 1, FrameSize, fp) != FrameSize) {  //每一个keyFrames[i]分配的是 (unsigned char) * FrameSize的大小，所以fread要读的每个数据项的字节数为1，可以表示每个像素点亮度范围0~255
               sprintf(errorText, "Input sequence %s is not enough", fileName);
               errorMsg(errorText);
           }
   
           //read u,v
           fread(buf, 1, uvSize, fp);
       }
       free(buf);
       fclose(fp);
   }
   
   void write_bmpheader(unsigned char *bitmap, int offset, int bytes, int value) {
       int i;
       for (i = 0; i < bytes; i++)
           bitmap[offset + i] = (value >> (i << 3)) & 0xFF;
   }
   
   unsigned char *convertToBmp(unsigned char *inputImg, int width, int height, int *ouputSize) {
   
       /*create a bmp format file*/
       int bitmap_x = (int)ceil((double)width * 3 / 4) * 4;
       unsigned char *bitmap = (unsigned char*)malloc(sizeof(unsigned char)*height*bitmap_x + 54);
   
       bitmap[0] = 'B';
       bitmap[1] = 'M';
       write_bmpheader(bitmap, 2, 4, height*bitmap_x + 54); //whole file size
       write_bmpheader(bitmap, 0xA, 4, 54); //offset before bitmap raw data
       write_bmpheader(bitmap, 0xE, 4, 40); //length of bitmap info header
       write_bmpheader(bitmap, 0x12, 4, width); //width
       write_bmpheader(bitmap, 0x16, 4, height); //height
       write_bmpheader(bitmap, 0x1A, 2, 1);
       write_bmpheader(bitmap, 0x1C, 2, 24); //bit per pixel
       write_bmpheader(bitmap, 0x1E, 4, 0); //compression
       write_bmpheader(bitmap, 0x22, 4, height*bitmap_x); //size of bitmap raw data
   
       for (int i = 0x26; i < 0x36; i++)
           bitmap[i] = 0;
   
       int k = 54;
       for (int i = height - 1; i >= 0; i--) {
           int j;
           for (j = 0; j < width; j++) {
               int index = i*width + j;
               for (int l = 0; l < 3; l++)
                   bitmap[k++] = inputImg[index];
           }
           j *= 3;
           while (j < bitmap_x) {
               bitmap[k++] = 0;
               j++;
           }
       }
   
       *ouputSize = k;
       return bitmap;
   }
   
   void saveToBmp(unsigned char *inputImg, int width, int height, char *outputFileName) {
       int size;
       unsigned char *bmp = convertToBmp(inputImg, width, height, &size);
       FILE *fp = fopen(outputFileName, "wb+");
       if (fp == NULL) {
           sprintf(errorText, "Could not open file: %s", outputFileName);
           errorMsg(errorText);
   
       }
       fwrite(bmp, 1, size, fp);
       fclose(fp);
       free(bmp);
   }
   
   int main() {
       int width = 120, height = 120;
   
       unsigned char **oriFrames;
       oriFrames = (unsigned char**)malloc(sizeof(unsigned char*) * FrameNum);
       for (int i = 0; i < FrameNum; i++) {
           oriFrames[i] = (unsigned char*)malloc(sizeof(unsigned char) * FrameSize);
       }
   
       ////Test写入
       //readSequence("E:\Research\YUV_Sequences\2D\BasketballPass_416x240_50\BasketballPass_416x240_50.yuv", oriFrames);
       //FILE *fp;
       //fp = fopen("E:\VS_Test_Code\cnblogData.txt", "w");
       //if (fp == NULL)
       //{
       //    exit(0);
       //}
       //for (int i = 0; i < FrameNum; i++)
       //{
       //    for (int j = 0; j < FrameSize; j++)
       //    {
       //        fprintf(fp, "%d,", oriFrames[i][j]);
       //    }
       //    fprintf(fp, "
   ");
       //}
       ////Test写入
   
       //Test读取
       FILE *fp;
       fp = fopen("E:\VS_Test_Code\cnblogData.txt", "r");
       if (fp == NULL)
       {
           exit(0);
       }
       for (int i = 0; i < FrameNum; i++)
       {
           for (int j = 0; j < FrameSize; j++)
           {
               fscanf(fp, "%d,", &oriFrames[i][j]);//必须和fprintf格式保持一致
           }
       }
       for (int i = 0; i < FrameNum; i++)
       {
           for (int j = 0; j < FrameSize; j++)
           {
               printf("%d ", oriFrames[i][j]);
           }
           printf("
   ");
       }
       //Test读取
   
       char imgName[30];
       for (int i = 0; i < FrameNum; i++) {
           sprintf(imgName, "F:\pictures\ReconsFrame%d.bmp", i);
           //矩阵oriFrames[i]可以是任何你想保存为图片的像素矩阵，这里是yuv视频图像每一帧的像素数据
           saveToBmp(oriFrames[i], width, height, imgName);
       }
       system("pause");
   }

2. 3.从图片中导入的数据保存为bmp图片
   从图片中导入图像数据，将其存储为像素矩阵，像素值的范围是0-255，分别对应从黑色到白色，并将像素矩阵保存为bmp图片。代码如下所示：

   #pragma warning(disable:4996)
   #include<iostream>
   #include<string>
   using namespace std;
   
   #define FrameSize 416*240  //视频帧大小
   #define FrameNum 300       //yuv帧数
   #define ET_SIZE 300
   char errorText[ET_SIZE];
   
   void errorMsg(const char *msg) 
   {
       printf("error:%s
   ", msg);
   #ifdef _WIN32
       system("pause");
   #endif
       exit(-1);
   
   }
   
   void readSequence(char *fileName, unsigned char **frames) 
   {
       FILE *fp = fopen(fileName, "rb");
       if (fp == NULL)
       {
           sprintf(errorText, "File %s doesn't exist
   ", fileName);
           errorMsg(errorText);
       }
       int uvSize = FrameSize / 2;            //H.264编解码获得的关键帧都是彩色序列，这里主要是提取亮度分量Y。
       unsigned char *buf = (unsigned char *)malloc(sizeof(unsigned char) * uvSize);
       for (int i = 0; i < FrameNum; i++) {
           //read y
           if (fread(frames[i], 1, FrameSize, fp) != FrameSize) {  //每一个keyFrames[i]分配的是 (unsigned char) * FrameSize的大小，所以fread要读的每个数据项的字节数为1，可以表示每个像素点亮度范围0~255
               sprintf(errorText, "Input sequence %s is not enough", fileName);
               errorMsg(errorText);
           }
           //read u,v
           fread(buf, 1, uvSize, fp);
       }
       free(buf);
       fclose(fp);
   }
   
   
   
   void write_bmpheader(unsigned char *bitmap, int offset, int bytes, int value) 
   {
       int i;
       for (i = 0; i < bytes; i++)
           bitmap[offset + i] = (value >> (i << 3)) & 0xFF;
   }
   
   unsigned char *convertToBmp(unsigned char *inputImg, int width, int height, int *ouputSize) 
   {
       /*create a bmp format file*/
       int bitmap_x = (int)ceil((double)width * 3 / 4) * 4;
       unsigned char *bitmap = (unsigned char*)malloc(sizeof(unsigned char)*height*bitmap_x + 54);
   
       bitmap[0] = 'B';
       bitmap[1] = 'M';
       write_bmpheader(bitmap, 2, 4, height*bitmap_x + 54); //whole file size
       write_bmpheader(bitmap, 0xA, 4, 54); //offset before bitmap raw data
       write_bmpheader(bitmap, 0xE, 4, 40); //length of bitmap info header
       write_bmpheader(bitmap, 0x12, 4, width); //width
       write_bmpheader(bitmap, 0x16, 4, height); //height
       write_bmpheader(bitmap, 0x1A, 2, 1);
       write_bmpheader(bitmap, 0x1C, 2, 24); //bit per pixel
       write_bmpheader(bitmap, 0x1E, 4, 0); //compression
       write_bmpheader(bitmap, 0x22, 4, height*bitmap_x); //size of bitmap raw data
   
       for (int i = 0x26; i < 0x36; i++)
           bitmap[i] = 0;
   
       int k = 54;
       for (int i = height - 1; i >= 0; i--) {
           int j;
           for (j = 0; j < width; j++) {
               int index = i*width + j;
               for (int l = 0; l < 3; l++)
                   bitmap[k++] = inputImg[index];
           }
           j *= 3;
           while (j < bitmap_x) {
               bitmap[k++] = 0;
               j++;
           }
       }
   
       *ouputSize = k;
       return bitmap;
   }
   
   void saveToBmp(unsigned char *inputImg, int width, int height, char *outputFileName) 
   {
       int size;
       unsigned char *bmp = convertToBmp(inputImg, width, height, &size);
       FILE *fp = fopen(outputFileName, "wb+");
       if (fp == NULL) {
           sprintf(errorText, "Could not open file: %s", outputFileName);
           errorMsg(errorText);
   
       }
       fwrite(bmp, 1, size, fp);
       fclose(fp);
       free(bmp);
   }
   
   int main() 
   {
       int width = 416, height = 240;
   
       unsigned char **oriFrames;
       oriFrames = (unsigned char**)malloc(sizeof(unsigned char*) * FrameNum);
       for (int i = 0; i < FrameNum; i++) {
           oriFrames[i] = (unsigned char*)malloc(sizeof(unsigned char) * FrameSize);
       }
   
       //获取图像的数据
       readSequence("E:\Research\YUV_Sequences\2D\BasketballPass_416x240_50\BasketballPass_416x240_50.yuv", oriFrames);
   
       char imgName[30];
       for (int i = 0; i < 10 /*FrameNum*/; i++) {
           sprintf(imgName, "F:\pictures\ReconsFrame%d.bmp", i);
           //矩阵oriFrames[i]可以是任何你想保存为图片的像素矩阵，这里是yuv视频图像每一帧的像素数据
           saveToBmp(oriFrames[i], width, height, imgName);
       }
   }

3. 4.参考文献

   https://blog.csdn.net/sinat_33718563/article/details/79424981
   https://blog.csdn.net/zzwtyds/article/details/75095698