Question

在这段代码中，我尝试从每个像素的RGB值相同的bmp文件中获取每个像素中的第一个字节（如ff ff ff），并将这些值放入矩阵中以供进一步操作。当调试器达到“从每个像素获取第一个字节”时，调试过程终止和项目2017.1.exe中的“0x0FDD053F（ucrtbased.dll）异常抛出：0xC0000005：访问冲突写入位置0xCDCDCDCD”出现。有什么问题？（这是我第一次使用bmp）感谢您的帮助！

#include <stdio.h>
#include <stdlib.h>

main() {
    int width, height, w_count, h_count, padding;
    int **pix_mat;
    int a;
    FILE * dust_pic;
    fopen_s(&dust_pic, "d2.bmp", "rb");
    if (!dust_pic)
        printf_s("not found");
    fseek(dust_pic, 18, SEEK_SET);
    fread(&width, sizeof(int), 1, dust_pic);// getting width
    fread(&height, sizeof(int), 1, dust_pic);// getting height
    // FIND PADDING
    a = width;
    if (a % 4 != 0)
        padding = 4 - (a % 4);
    else
    padding = 0;

    //making matrix for pixels
    pix_mat = (int**)malloc(sizeof(int*)*height);
    for (h_count = 0; h_count < height; h_count++)
        pix_mat[h_count] = (int*)malloc(sizeof(int)*width);

    fseek(dust_pic, 54, SEEK_SET);
    // getting the first byte from each pixel
    for (h_count = 0; h_count < height; h_count++)
    {
        for (w_count = 0; w_count < width; w_count++)
        {
            fread(pix_mat[w_count][h_count], sizeof(char), 1, dust_pic);
            fseek(dust_pic, 2, SEEK_CUR);
        }
        fseek(dust_pic, padding, SEEK_CUR);
    }
    fclose(dust_pic);
    // print the matrix.
    for (h_count = 0; h_count < height; h_count++)
    {
        for (w_count = 0; w_count < width; w_count++)
            printf_s("[%d],[%d]=%d  ", w_count, h_count, pix_mat[w_count][h_count]);
        printf("\n");
    }
    // free array
    for (h_count = 0; h_count < height; h_count++)
        free(pix_mat[h_count]);
    free(pix_mat);
}

Answer 1

以下提议的代码：

干净地编译
正确检查错误
在任何错误事件退出之前正确清理
从文件中正确读取正确大小的数据，并将该数据保存到正确声明的数组
正确引用内存中像素矩阵的行和列
不会更正有关像素宽度，偏移到文件中像素等的假设

现在是代码

#include <stdio.h>  // fopen(), fclose(), perror(), fseek(), SEEK_SET
#include <stdlib.h> // exit(), EXIT_FAILURE, malloc(), calloc(), free()

// prototypes
void cleanup( FILE *dust_pic, size_t height, char **pix_mat );


int main( void )
{
    size_t width, height, w_count, h_count;
    long padding;
    char **pix_mat;

    FILE * dust_pic;
    dust_pic = fopen("d2.bmp", "rb");
    if (!dust_pic)
    {
        perror( "fopen failed" );
        exit( EXIT_FAILURE );
    }

    // implied else, fopen_s successful

    fseek(dust_pic, 18, SEEK_SET);
    // check for error

    if( 1 != fread(&width, sizeof(int), 1, dust_pic) )// getting width
    {
        perror( "fread for width of image, in pixels, failed" );
        fclose( dust_pic );
        exit( EXIT_FAILURE );
    }

    // implied else, fread successful

    if( 1 != fread(&height, sizeof(int), 1, dust_pic) )// getting height
    {
        perror( "fread for height of image, in pixels, failed" );
        fclose( dust_pic );
        exit( EXIT_FAILURE );
    }

    // implied else, fread successful

    // calculate PADDING
    if ( width % 4 != 0)
        padding = (long)(4 - (width % 4));
    else
        padding = 0;

    //making matrix for pixels
    pix_mat = calloc(height, sizeof(char*));
    // check for malloc status
    if( !pix_mat )
    {
        perror( "calloc for array of pointers to char failed" );
        fclose( dust_pic );
        exit( EXIT_FAILURE );
    }

    // implied else, calloc successful

    for (h_count = 0; h_count < height; h_count++)
    {
        pix_mat[h_count] = malloc(sizeof(char)*width);
        // check for malloc status
        if( !pix_mat[h_count] )
        {
            perror( "malloc failed" );
            fclose( dust_pic );
            exit( EXIT_FAILURE );
        }

        // implied else, malloc successful
    }

    // jump to beginning of pixel data in file
    if( -1 == fseek(dust_pic, 54, SEEK_SET) )
    {
        perror( "fseek to start of pixel data failed" );
        cleanup( dust_pic, height, pix_mat );
        exit( EXIT_FAILURE );
    }

    // implied else, fseek successful

    // get the first byte (red) from each pixel
    for (h_count = 0; h_count < height; h_count++)
    {
        for (w_count = 0; w_count < width; w_count++)
        {
            if( 1 != fread( &((pix_mat[h_count])[w_count]), sizeof(char), 1, dust_pic) )
            {
                perror( "fread of 'red' pixel value failed" );
                cleanup( dust_pic, height, pix_mat );
                exit( EXIT_FAILURE );
            }

            // implied else, fread successful

            if( -1 == fseek(dust_pic, 2, SEEK_CUR) )
            {
                perror( "fseek to skip green/blue pixels failed" );
                cleanup( dust_pic, height, pix_mat );
                exit( EXIT_FAILURE );
            }

            // implied else, fseek successful
        }

        if( -1 == fseek(dust_pic, padding, SEEK_CUR) )
        {
            perror( "fseek to skip padding failed" );
            cleanup( dust_pic, height, pix_mat );
            exit( EXIT_FAILURE );
        }

        // implied else, fseek successful
    }


    // print the matrix.
    for (h_count = 0; h_count < height; h_count++)
    {
        for (w_count = 0; w_count < width; w_count++)
            printf("[%lu],[%lu]=%3.3d  ", h_count, w_count, (pix_mat[h_count])[w_count]);
        printf("\n");
    }

    cleanup( dust_pic, height, pix_mat );
} // end function: main


void cleanup( FILE *dust_pic, size_t height, char **pix_mat )
{
    // free array
    for (size_t h_count = 0; h_count < height; h_count++)
        free(pix_mat[h_count]);
    free(pix_mat);

    fclose( dust_pic );
} // end function: cleanup

项目2017.1.exe中0x0FDD053F（ucrtbased.dll）引发的bmp文件异常错误：0xC0000005：访问冲突写入位置0xCDCDCDCD

1 个答案: