100 lines
4.2 KiB
C++
100 lines
4.2 KiB
C++
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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typedef int BOOL;
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#define TRUE 1
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#define FALSE 0
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//位图文件头结构体
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//这个结构体的长度是固定的14个字节。
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//考虑到结构体的字节对齐，将bfType单独提取出来，否则会造成该结构体为16个字节。
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static unsigned short bfType = 0x4D42;//指定文件类型，必须是0x424D，
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//即字符串“BM”，也就是说所有.bmp文件的头两个字节都是“BM”。
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//'BM'表示这是Windows支持的位图格式。
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typedef struct {
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unsigned int bfSize; //指定文件大小，以字节为单位，包括这14个字节。
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unsigned short bfReserved1; //为保留字，不用考虑
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unsigned short bfReserved2; //为保留字，不用考虑
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unsigned int bfOffBits; //位图文件头到数据的偏移量，以字节为单位
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}BmpHead;
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//位图信息头结构体
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typedef struct {
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unsigned int biSize; //该结构大小，字节为单位，一般为40个字节
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unsigned int biWidth; //指定图象的宽度，单位是象素。
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unsigned int biHeight; //指定图象的高度，单位是象素。
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//注：这个值除了用于描述图像的高度之外，它还有另一个用处，
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//就是指明该图像是倒向的位图，还是正向的位图。
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//如果该值是一个正数，说明图像是倒向的，如果该值是个负数，则说明图像是正向的。
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//大多数的BMP文件都是倒向的位图，也就是高度值是一个正数。
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unsigned short biPlanes; //为目标设备说明颜色平面数，必须为1，不用考虑
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unsigned short biBitCount; //颜色深度，每个象素所需要的位数
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unsigned int biCompression; //位图的压缩类型
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unsigned int biSizeImage; //位图的大小，以字节为单位
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unsigned int biXPelsPerMeter; //位图水平分辨率，每米像素数
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unsigned int biYPelsPerMeter; //位图垂直分辨率，每米像素数
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unsigned int biClrUsed; //位图实际使用的颜色表中的颜色数
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unsigned int biClrImportant; //位图显示过程中重要的颜色数
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}InfoHead;
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BOOL rgb24_to_bmp(const char *file, int width, int height)
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{
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if (file == NULL) {
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return FALSE;
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}
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FILE *fpRgb24 = fopen(file, "rb");
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FILE *fpBmp = fopen("./out/output_rgb24_to_bmp.bmp", "wb");
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//从文件中读取RGB数据
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unsigned char *rgb24Buf = (unsigned char *)malloc(width*height*3);
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memset(rgb24Buf, 0, width*height*3);
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fread(rgb24Buf, 1, width*height*3, fpRgb24);
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int headSize = sizeof(BmpHead) + sizeof(InfoHead) + sizeof(bfType);
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BmpHead bmpHead = {0};
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InfoHead bmpInfoHead = {0};
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bmpHead.bfSize = width*height*3 + headSize;
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bmpHead.bfOffBits = headSize;
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bmpInfoHead.biSize = sizeof(InfoHead);
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bmpInfoHead.biWidth = width;
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bmpInfoHead.biHeight = -height;//BMP存储像素数据在Y轴方向从下到上。
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bmpInfoHead.biPlanes = 1;
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bmpInfoHead.biBitCount = 24;
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bmpInfoHead.biSizeImage = width*height*3;
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fwrite(&bfType, 1, sizeof(bfType), fpBmp);
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fwrite(&bmpHead, 1, sizeof(bmpHead), fpBmp);
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fwrite(&bmpInfoHead, 1, sizeof(bmpInfoHead), fpBmp);
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//BMP采用的是小端（Little Endian）存储方式。
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//这种存储方式中“RGB24”格式的像素的分量存储的先后顺序为B、G、R。
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//由于RGB24格式存储的顺序是R、G、B，所以需要将“R”和“B”顺序作一个调换再进行存储。
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for (int i=0; i<height; i++) {
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for (int j=0; j<width; j++) {
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unsigned char tmp = rgb24Buf[(i*width+j)*3+2];
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rgb24Buf[(i*width+j)*3+2] = rgb24Buf[(i*width+j)*3+0];
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rgb24Buf[(i*width+j)*3+0] = tmp;
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}
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}
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fwrite(rgb24Buf, width*height*3, 1, fpBmp);
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free(rgb24Buf);
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fclose(fpBmp);
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fclose(fpRgb24);
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return TRUE;
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}
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int main(int argc, char *argv[])
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{
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if (argc == 4) {
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rgb24_to_bmp(argv[1], atoi(argv[2]), atoi(argv[3]));
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}
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return 0;
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}
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