我似乎在一项小型编程任务中遇到了困难。（请不要告诉我如何解决整个问题；我只想知道如何将每个字节设置为红色）。
我的代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include "bmp.h"
int main(int argc, char* argv[])
{
// ensure proper usage
//if (argc != 3)
//{
// printf("Usage: copy infile outfile\n");
// return 1;
//}
// remember filenames
//char* infile = argv[1];
//char* outfile = argv[2];
char* infile = GetString();
char* outfile = GetString();
// open input file
FILE* inptr = fopen(infile, "r");
if (inptr == NULL)
{
printf("Could not open %s.\n", infile);
return 2;
}
// open output file
FILE* outptr = fopen(outfile, "w");
if (outptr == NULL)
{
fclose(inptr);
fprintf(stderr, "Could not create %s.\n", outfile);
return 3;
}
// read infile's BITMAPFILEHEADER
BITMAPFILEHEADER bf;
fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);
// read infile's BITMAPINFOHEADER
BITMAPINFOHEADER bi;
fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);
// ensure infile is (likely) a 24-bit uncompressed BMP 4.0
if (bf.bfType != 0x4d42 || bf.bfOffBits != 54 || bi.biSize != 40 ||
bi.biBitCount != 24 || bi.biCompression != 0)
{
fclose(outptr);
fclose(inptr);
fprintf(stderr, "Unsupported file format.\n");
return 4;
}
// write outfile's BITMAPFILEHEADER
fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);
// write outfile's BITMAPINFOHEADER
fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr);
// determine padding for scanlines
int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
// iterate over infile's scanlines
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
{
// iterate over pixels in scanline
for (int j = 0; j < bi.biWidth; j++)
{
// temporary storage
RGBTRIPLE triple;
// read RGB triple from infile
fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
triple.rgbtRed = 'ff'
// write RGB triple to outfile
fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
}
// skip over padding, if any
fseek(inptr, padding, SEEK_CUR);
// then add it back (to demonstrate how)
for (int k = 0; k < padding; k++)
fputc(0x00, outptr);
}
// close infile
fclose(inptr);
// close outfile
fclose(outptr);
// that's all folks
return 0;
}
bmp.h 是
#include <stdint.h>
/**
* Common Data Types
*
* The data types in this section are essentially aliases for C/C++
* primitive data types.
*
* Adapted from http://msdn.microsoft.com/en-us/library/cc230309(PROT.10).aspx.
* See http://en.wikipedia.org/wiki/Stdint.h for more on stdint.h.
*/
typedef uint8_t BYTE;
typedef uint32_t DWORD;
typedef int32_t LONG;
typedef uint16_t WORD;
/**
* BITMAPFILEHEADER
*
* The BITMAPFILEHEADER structure contains information about the type, size,
* and layout of a file that contains a DIB [device-independent bitmap].
*
* Adapted from http://msdn.microsoft.com/en-us/library/dd183374(VS.85).aspx.
*/
typedef struct
{
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} __attribute__((__packed__))
BITMAPFILEHEADER;
/**
* BITMAPINFOHEADER
*
* The BITMAPINFOHEADER structure contains information about the
* dimensions and color format of a DIB [device-independent bitmap].
*
* Adapted from http://msdn.microsoft.com/en-us/library/dd183376(VS.85).aspx.
*/
typedef struct
{
DWORD biSize;
LONG biWidth;
LONG biHeight;
WORD biPlanes;
WORD biBitCount;
DWORD biCompression;
DWORD biSizeImage;
LONG biXPelsPerMeter;
LONG biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} __attribute__((__packed__))
BITMAPINFOHEADER;
/**
* RGBTRIPLE
*
* This structure describes a color consisting of relative intensities of
* red, green, and blue.
*
* Adapted from http://msdn.microsoft.com/en-us/library/aa922590.aspx.
*/
typedef struct
{
BYTE rgbtBlue;
BYTE rgbtGreen;
BYTE rgbtRed;
} __attribute__((__packed__))
RGBTRIPLE;
注意：我没有 GetString 的代码，但请假设它会以char*.
我遇到的问题是尝试将每个像素的 rgbtRed 值转换为极红色；我不知道该怎么做。请只提供我如何转换 rgbtRed？
更新：拼图
欢迎来到都铎大厦。你的主人，约翰·博迪先生，过早地结束了——他是犯规的受害者。要赢得这场比赛，您必须确定 whodunit。
对您来说很不幸（尽管对 Boddy 先生来说更不幸），您拥有的唯一证据是一个 24 位 BMP 文件，名为线索.bmp，如下图所示，Boddy 先生在他的最后时刻在他的计算机上快速启动了该文件。隐藏在这个文件的红色“噪音”中的是一张 whodunit 的图画。
你很久以前就扔掉了那块儿时的红色塑料，它可以为你解开这个谜团，所以你必须以计算机科学家的身份来攻击它。