不使用opencv，用c语言提取bmp图像RGB值

可以使用C语言的标准库函数来提取BMP图像的RGB值。首先需要读取BMP文件头信息，然后根据文件头信息中的宽度和高度信息，逐行读取像素数据，再根据像素数据中的颜色分量信息提取RGB值。以下是一个简单的示例代码：

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

#pragma pack(push, 1)
typedef struct {
    uint16_t type;
    uint32_t size;
    uint16_t reserved1;
    uint16_t reserved2;
    uint32_t offset;
} bmp_file_header_t;

typedef struct {
    uint32_t size;
    int32_t width;
    int32_t height;
    uint16_t planes;
    uint16_t bit_count;
    uint32_t compression;
    uint32_t size_image;
    int32_t x_pels_per_meter;
    int32_t y_pels_per_meter;
    uint32_t clr_used;
    uint32_t clr_important;
} bmp_info_header_t;
#pragma pack(pop)

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Usage: %s <bmp_file>\n", argv[0]);
        return 1;
    }

    FILE *fp = fopen(argv[1], "rb");
    if (!fp) {
        printf("Failed to open file: %s\n", argv[1]);
        return 1;
    }

    bmp_file_header_t file_header;
    bmp_info_header_t info_header;

    fread(&file_header, sizeof(file_header), 1, fp);
    fread(&info_header, sizeof(info_header), 1, fp);

    if (file_header.type != 0x4D42) {
        printf("Invalid BMP file format\n");
        return 1;
    }

    if (info_header.bit_count != 24) {
        printf("Unsupported color depth: %d\n", info_header.bit_count);
        return 1;
    }

    int width = info_header.width;
    int height = info_header.height;
    int row_size = (width * 3 + 3) & ~3; // BMP行字节数为4的倍数

    uint8_t *data = malloc(row_size * height);
    if (!data) {
        printf("Failed to allocate memory\n");
        return 1;
    }

    fseek(fp, file_header.offset, SEEK_SET);
    fread(data, row_size, height, fp);

    fclose(fp);

    for (int y = 0; y < height; y++) {
        for (int x = 0; x < width; x++) {
            uint8_t *pixel = data + y * row_size + x * 3;
            uint8_t r = pixel[2];
            uint8_t g = pixel[1];
            uint8_t b = pixel[0];
            printf("(%d,%d): R=%d, G=%d, B=%d\n", x, y, r, g, b);
        }
    }

    free(data);

    return 0;
}

这个程序可以读取一个BMP文件，并输出每个像素的RGB值。注意，由于BMP文件的行字节数为4的倍数，因此需要使用位运算来计算每行的字节数。