写一个基于gec6818的电子相册显示代码

以下是一个基于GEC6818的电子相册显示代码的示例：

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/fb.h>
#include <linux/input.h>

#define FB_DEVICE "/dev/fb0"
#define BMP_FILE "example.bmp"

typedef struct BMPFileHeader {
    uint16_t fileType;      // 文件类型，必须是0x424D，即字符“BM”
    uint32_t fileSize;      // 整个BMP文件的大小
    uint16_t reserved1;     // 保留，必须设置为0
    uint16_t reserved2;     // 保留，必须设置为0
    uint32_t bmpOffset;     // BMP图像数据的起始位置
} BMPFileHeader;

typedef struct BMPInfoHeader {
    uint32_t infoSize;      // 本结构体的大小，必须是40
    int32_t bmpWidth;       // BMP图像的宽度
    int32_t bmpHeight;      // BMP图像的高度
    uint16_t planes;        // BMP图像的平面数，必须是1
    uint16_t bitCount;      // 每个像素的比特数，必须是24
    uint32_t compression;   // 压缩类型，0表示不压缩
    uint32_t imageSize;     // BMP图像数据的大小
    int32_t xPixelsPerMeter;// 水平分辨率，像素/米
    int32_t yPixelsPerMeter;// 垂直分辨率，像素/米
    uint32_t colorsUsed;    // 实际使用的颜色数，0表示使用所有颜色
    uint32_t colorsImportant;  // 重要颜色数，0表示所有颜色都重要
} BMPInfoHeader;

int main() {
    int fbfd = open(FB_DEVICE, O_RDWR);
    if (fbfd == -1) {
        perror("open framebuffer device");
        exit(EXIT_FAILURE);
    }

    struct fb_var_screeninfo vinfo;
    struct fb_fix_screeninfo finfo;

    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1) {
        perror("get variable screen info");
        exit(EXIT_FAILURE);
    }

    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1) {
        perror("get fixed screen info");
        exit(EXIT_FAILURE);
    }

    size_t screenSize = vinfo.yres * finfo.line_length;
    void *fbp = mmap(NULL, screenSize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
    if (fbp == MAP_FAILED) {
        perror("mmap framebuffer");
        exit(EXIT_FAILURE);
    }

    int bmpfd = open(BMP_FILE, O_RDONLY);
    if (bmpfd == -1) {
        perror("open BMP file");
        exit(EXIT_FAILURE);
    }

    BMPFileHeader header;
    BMPInfoHeader info;

    if (read(bmpfd, &header, sizeof(header)) != sizeof(header)) {
        perror("read BMP header");
        exit(EXIT_FAILURE);
    }

    if (read(bmpfd, &info, sizeof(info)) != sizeof(info)) {
        perror("read BMP info");
        exit(EXIT_FAILURE);
    }

    if (header.fileType != 0x4D42) {
        fprintf(stderr, "invalid BMP file type\n");
        exit(EXIT_FAILURE);
    }

    if (info.infoSize != sizeof(info)) {
        fprintf(stderr, "invalid BMP info size\n");
        exit(EXIT_FAILURE);
    }

    if (info.bitCount != 24) {
        fprintf(stderr, "only support 24-bit BMP files\n");
        exit(EXIT_FAILURE);
    }

    if (lseek(bmpfd, header.bmpOffset, SEEK_SET) == -1) {
        perror("seek BMP image data");
        exit(EXIT_FAILURE);
    }

    size_t bmpDataSize = info.imageSize;
    void *bmpData = malloc(bmpDataSize);
    if (bmpData == NULL) {
        perror("allocate BMP data buffer");
        exit(EXIT_FAILURE);
    }

    if (read(bmpfd, bmpData, bmpDataSize) != bmpDataSize) {
        perror("read BMP image data");
        exit(EXIT_FAILURE);
    }

    int x, y;

    for (y = 0; y < info.bmpHeight; y++) {
        for (x = 0; x < info.bmpWidth; x++) {
            int pos = (y * info.bmpWidth + x) * 3;
            uint8_t b = ((uint8_t *) bmpData)[pos];
            uint8_t g = ((uint8_t *) bmpData)[pos + 1];
            uint8_t r = ((uint8_t *) bmpData)[pos + 2];
            uint32_t color = (r << vinfo.red.offset) | (g << vinfo.green.offset) | (b << vinfo.blue.offset);
            *((uint32_t *) (fbp + (y + vinfo.yoffset) * finfo.line_length + (x + vinfo.xoffset) * sizeof(uint32_t))) = color;
        }
    }

    free(bmpData);
    munmap(fbp, screenSize);
    close(bmpfd);
    close(fbfd);

    return 0;
}

此示例代码打开一个BMP文件，将其解码并显示在GEC6818板子的屏幕上。你可以替换`BMP_FILE`变量的值为你想要显示的BMP文件的路径。注意，此代码仅支持24位BMP文件。