Question

我似乎在一个小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;
}

和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，但请假设它将返回一个字符串char*。

我遇到的问题是尝试将每个像素的rgbtRed值转换为极端红色;我不知道该怎么做。请告诉我如何转换rgbtRed？

更新：拼图

欢迎来到都铎大厦。你的主人约翰博迪先生遇到了一个不合时宜的结局 - 他是犯规的受害者。要赢得这场比赛，你必须确定whodunit。

不幸的是你（虽然Boddy先生更为不幸），你唯一的证据就是一个名为clue.bmp的24位BMP文件，如下图所示，Boddy先生在最后时刻掀起了他的电脑。隐藏在这个文件中的红色“噪音”是一个奇怪的图画。

enter image description here

你很久以前就把那块红色的塑料从童年时起扔掉了，为你解开这个谜团，所以你必须以计算机科学家的身份攻击它。

Answer 1

删除单引号。 'ff'是实现定义的（或未定义的）整数，0xff是十六进制常量。

该行应该是问题

            triple.rgbtRed = 0xff;

Answer 2

在白色图像上获得漂亮的天蓝色：

triple.rgbtBlue = 0xff;

triple.rgbtGreen = 0xff;

如果你想要红色比例：

triple.rgbtBlue =  0x00;

triple.rgbtGreen = 0x00;

如果你想要紫色比例：

triple.rgbtBlue = 0xff;

triple.rgbtGreen = 0x00;

转换此代码中的像素

2 个答案: