损坏/不支持的.bmp文件

Question

我需要为学校项目实现盒子模糊算法，然后在线发现了该算法。我的问题是，完成算法后，我无法打开“ result.bmp”文件。 它说该文件要么损坏或损坏，而且我似乎找不到此问题的原因。

代码：

    FILE* fIn = fopen("test.bmp", "r");         // Input File name
    FILE* fOut = fopen("result.bmp", "w+");             // Output File name

    int i, j, y, x;
    unsigned char byte[54];


    for (i = 0; i < 54; i++)                        // read the 54 byte header from fIn
    {
        byte[i] = fgetc(fIn);
    }

    fwrite(byte, sizeof(unsigned char), 54, fOut);          // write the header back

    // extract image height, width and bitDepth from imageHeader 
    int height = *(int*)&byte[18];
    int width = *(int*)&byte[22];
    int bitDepth = *(int*)&byte[28];

    printf("width: %d\n", width);
    printf("height: %d\n", height);

    int size = height * width;

    unsigned char** buffer = (unsigned char**)malloc(size * sizeof(unsigned char*));
    for (int i = 0; i < size; i++)
        buffer[i] = (unsigned char*)malloc(3 * sizeof(unsigned char));

    unsigned char** out = (unsigned char**)malloc(size * sizeof(unsigned char*));
    for (int i = 0; i < size; i++)
        out[i] = (unsigned char*)malloc(3 * sizeof(unsigned char));

    for (i = 0; i < size; i++)                      
    {
        buffer[i][2] = getc(fIn);                   // blue
        buffer[i][1] = getc(fIn);                   // green
        buffer[i][0] = getc(fIn);                   // red
    }


    float v = 1.0 / 9.0;                        // initialize the blurring kernel
    float kernel[3][3] = { {v,v,v},
                        {v,v,v},
                        {v,v,v} };

    for (x = 1; x < height - 1; x++)
    {
        for (y = 1; y < width - 1; y++)
        {
            float sum0 = 0.0;
            float sum1 = 0.0;
            float sum2 = 0.0;
            for (i = -1; i <= 1; i++)
            {
                for (j = -1; j <= 1; j++)
                {
                    // matrix multiplication with kernel with every color plane
                    sum0 = sum0 + (float)kernel[i + 1][j + 1] * buffer[(x + i) * width + (y + j)][0];
                    sum1 = sum1 + (float)kernel[i + 1][j + 1] * buffer[(x + i) * width + (y + j)][1];
                    sum2 = sum2 + (float)kernel[i + 1][j + 1] * buffer[(x + i) * width + (y + j)][2];
                }
            }
            out[(x)*width + (y)][0] = (unsigned char)sum0;
            out[(x)*width + (y)][1] = (unsigned char)sum1;
            out[(x)*width + (y)][2] = (unsigned char)sum2;
        }
    }


    for (i = 0; i < size; i++)                      //write image data back to the file
    {
        fputc(out[i][2], fOut);
        fputc(out[i][1], fOut);
        fputc(out[i][0], fOut);
    }

该算法成功读取输入图像的宽度和高度，它创建输出文件，但无法打开文件。

Answer 1

您的代码非常接近，但存在一些问题：

• 您可以根据4字节对齐来计算每行的字节数
  使用（（width * 3 + 3） / 4） * 4 < / code>。
• width和高度的附接反之亦然。
• 您不应施放malloc（）的返回值。
• BMP文件标头由BMP文件标头（14个字节固定）
  和dib头（可变大小）。由于存储DIB标头的大小
  在DIB标头的启动4个字节中，让我们读取18个字节（= 14 + 4）
  首先，确定剩余的标头尺寸，然后读取其余的DIB标头。

然后，修改版本看起来像：

#include <stdio.h>
#include <stdlib.h>
#define INFILE "test.bmp"       // input file name
#define OUTFILE "result.bmp"    // output file name
#define HEADER1 (14 + 4)        // Bitmap File Header + word for header size
#define HEADER2 (124 - 4)       // DIB (Information) File Header - word for header size

int main()
{
    FILE *fIn = fopen(INFILE, "r");
    if (fIn == NULL) {
        perror(INFILE);
        exit(1);
    }
    FILE *fOut = fopen(OUTFILE, "w+");
    if (fOut == NULL) {
        perror(OUTFILE);
        exit(1);
    }

    int i, j, y, x;
    int dibsize;                                        // size of DIB Header
    unsigned char header1[HEADER1];
    unsigned char header2[HEADER2];

    fread(header1, sizeof(unsigned char), HEADER1, fIn);    // read file header + DIB header size
    dibsize = *(int *)&header1[14];                         // size of DIB header
    fwrite(header1, sizeof(unsigned char), HEADER1, fOut);  // write the header back

    fread(header2, sizeof(unsigned char), dibsize - 4, fIn);    // read remaining DIB header except for the word for the header size
    fwrite(header2, sizeof(unsigned char), dibsize - 4, fOut);  // write the header back

    // extract image height, width and bitDepth from imageHeader 
    int width = *(int *)&header2[0];
    int height = *(int *)&header2[4];
    int bitDepth = *(int *)&header2[20];
    int bytesperline = ((width * 3 + 3) / 4) * 4;       // bytes per line including 4-byte alignment

    printf("width: %d\n", width);
    printf("height: %d\n", height);
//  printf("bytesperline: %d\n", bytesperline);

    int size = height * width;

    unsigned char **buffer = malloc(size * sizeof(unsigned char *));
    for (int i = 0; i < size; i++)
        buffer[i] = malloc(3 * sizeof(unsigned char));

    unsigned char **out = malloc(size * sizeof(unsigned char *));
    for (int i = 0; i < size; i++)
        out[i] = malloc(3 * sizeof(unsigned char));

    for (i = 0; i < height; i++)
    {
        for (j = 0; j < width; j++)
        {
            buffer[i * width + j][2] = getc(fIn);       // blue
            buffer[i * width + j][1] = getc(fIn);       // green
            buffer[i * width + j][0] = getc(fIn);       // red
        }
        for (j = width * 3; j < bytesperline; j++)      // zero padding for 4-byte alignment
        {
            getc(fIn);
        }
    }

    float v = 1.0 / 9.0;                                // initialize the blurring kernel
    float kernel[3][3] = { {v,v,v},
                        {v,v,v},
                        {v,v,v} };

    for (x = 1; x < height - 1; x++)
    {
        for (y = 1; y < width - 1; y++)
        {
            float sum0 = 0.0;
            float sum1 = 0.0;
            float sum2 = 0.0;
            for (i = -1; i <= 1; i++)
            {
                for (j = -1; j <= 1; j++)
                {
                    // matrix multiplication with kernel with every color plane
                    sum0 = sum0 + (float)kernel[i + 1][j + 1] * buffer[(x + i) * width + (y + j)][0];
                    sum1 = sum1 + (float)kernel[i + 1][j + 1] * buffer[(x + i) * width + (y + j)][1];
                    sum2 = sum2 + (float)kernel[i + 1][j + 1] * buffer[(x + i) * width + (y + j)][2];
                }
            }
            out[x * width + y][0] = (unsigned char)sum0;
            out[x * width + y][1] = (unsigned char)sum1;
            out[x * width + y][2] = (unsigned char)sum2;
        }
    }

    for (i = 0; i < height; i++)                        // write image data back to the file
    {
        for (j = 0; j < width; j++)
        {
            fputc(out[i * width + j][2], fOut);         // blue
            fputc(out[i * width + j][1], fOut);         // green
            fputc(out[i * width + j][0], fOut);         // red
        }
        for (j = width * 3; j < bytesperline; j++)      // zero padding for 4-byte alignment
        {
            fputc(0, fOut);
        }
    }

    fclose(fIn);
    fclose(fOut);
    return 0;
}