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. 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：
   

     1 #pragma warning(disable:4996)
     2 #include<iostream>
     3 #include<string>
     4 using namespace std;
     5 
     6 //#define FrameSize 960*960  //视频帧大小
     7 int width = 120, height = 120;
     8 #define FrameNum 300       //yuv帧数
     9 static const double S_PI = 3.14159265358979323846;
    10 #define scos(x)         cos((double)(x))
    11 #define stan(x)         tan((double)(x))
    12 #define ssqrt(x)        sqrt((double)(x))
    13 #define ET_SIZE 300
    14 char errorText[ET_SIZE];
    15 
    16 void errorMsg(const char *msg) 
    17 {
    18     printf("error:%s\n", msg);
    19 #ifdef _WIN32
    20     system("pause");
    21 #endif
    22     exit(-1);
    23 }
    24 
    25 void readSequence(unsigned char *frames)
    26 {
    27     //Test start    
    28     for (int y = 0; y < height; y++)
    29     {
    30         for (int x = 0; x < width; x++)
    31         {
    32             //使用公式生成像素数据
    33             float pu0 = (float)((2.0*(x + 0.5)) / width - 1.0);
    34             float pv0 = (float)((2.0*(y + 0.5)) / height - 1.0);
    35 
    36             double tu0 = stan(pu0*S_PI / 4.0);
    37             double tv0 = stan(pv0*S_PI / 4.0);
    38             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));
    39 
    40             //将值从(0，1)放大到(0，255)
    41             value= 255.0*value;
    42             //将值从(128，255)放大到(0，255),增加图像对比度
    43             frames[y*width + x] = 2.0*value- 255.0;
    44         }
    45     }
    46 }
    47 
    48 void write_bmpheader(unsigned char *bitmap, int offset, int bytes, int value) 
    49 {
    50     int i;
    51     for (i = 0; i < bytes; i++)
    52         bitmap[offset + i] = (value >> (i << 3)) & 0xFF;
    53 }
    54 
    55 unsigned char *convertToBmp(unsigned char *inputImg, int width, int height, int *ouputSize) 
    56 {
    57     /*create a bmp format file*/
    58     int bitmap_x = (int)ceil((double)width * 3 / 4) * 4;
    59     unsigned char *bitmap = (unsigned char*)malloc(sizeof(unsigned char)*height*bitmap_x + 54);
    60 
    61     bitmap[0] = 'B';
    62     bitmap[1] = 'M';
    63     write_bmpheader(bitmap, 2, 4, height*bitmap_x + 54); //whole file size
    64     write_bmpheader(bitmap, 0xA, 4, 54); //offset before bitmap raw data
    65     write_bmpheader(bitmap, 0xE, 4, 40); //length of bitmap info header
    66     write_bmpheader(bitmap, 0x12, 4, width); //width
    67     write_bmpheader(bitmap, 0x16, 4, height); //height
    68     write_bmpheader(bitmap, 0x1A, 2, 1);
    69     write_bmpheader(bitmap, 0x1C, 2, 24); //bit per pixel
    70     write_bmpheader(bitmap, 0x1E, 4, 0); //compression
    71     write_bmpheader(bitmap, 0x22, 4, height*bitmap_x); //size of bitmap raw data
    72 
    73     for (int i = 0x26; i < 0x36; i++)
    74         bitmap[i] = 0;
    75     int k = 54;
    76     for (int i = height - 1; i >= 0; i--) {
    77         int j;
    78         for (j = 0; j < width; j++) {
    79             int index = i*width + j;
    80             for (int l = 0; l < 3; l++)
    81                 bitmap[k++] = inputImg[index];
    82         }
    83         j *= 3;
    84         while (j < bitmap_x) {
    85             bitmap[k++] = 0;
    86             j++;
    87         }
    88     }
    89     *ouputSize = k;
    90     return bitmap;
    91 }
    92 
    93 void saveToBmp(unsigned char *inputImg, int width, int height, char *outputFileName) 
    94 {
    95     int size;
    96     unsigned char *bmp = convertToBmp(inputImg, width, height, &size);
    97     FILE *fp = fopen(outputFileName, "wb+");
    98     if (fp == NULL) {
    99         sprintf(errorText, "Could not open file: %s", outputFileName);
   100         errorMsg(errorText);
   101     }
   102     fwrite(bmp, 1, size, fp);
   103     fclose(fp);
   104     free(bmp);
   105 }
   106 int main() 
   107 {
   108     unsigned char *oriFrames;
   109     oriFrames = (unsigned char*)malloc(sizeof(unsigned char) * width * height);
   110     readSequence(oriFrames);
   111 
   112     char imgName[30];
   113     sprintf(imgName, "F:\\pictures\\Bitmap_Weight_Map_Convex2.bmp");
   114     //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
   115     saveToBmp(oriFrames, width, height, imgName);
   116     //system("pause");
   117 }

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