纯C++代码实现将像素矩阵保存为bmp图片

秒速五厘米 2022-05-30 02:45 502阅读 0赞

用C++代码将像素矩阵保存为图片，这里以读取yuv序列视频帧为例进行分析，假设4:2:0yuv序列有300帧，则首先需要将每一视频帧保存在一个像素矩阵中，然后将每一个矩阵保存为图片，最终会有300个bmp图片。

纯C++代码如下：

saveToPicture.cpp

#include<iostream>
    #include<string>
    using namespace std;
    
    #define FrameSize 176*144  //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\n", 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\n", 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 = 176, height = 144;
    	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);
    	}
    	readSequence("foreman_qcif_300.yuv", oriFrames);
    	
    	char imgName[30];
    	for (int i = 0; i < FrameNum; i++) {
    		sprintf(imgName,"./picture/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);  
    	}
    }