在LCD屏内显示任意尺寸任意大小的bmp图像

定义结构体

/****************************************************************************
 *
 * file name: ShowBmp.c
 * author   : Dazz
 * date     : 2024-05-12
 * function : 在LCD上显示任意大小任意尺寸的bmp图片
 * note     : None
 * CopyRight (c)  2024-202x   [email protected]   All Right Reseverd
 *
 ****************************************************************************/

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

#pragma pack(1)

// 定义BMP文件头部结构
typedef struct
{
  unsigned short bfType;
  unsigned int bfSize;
  unsigned short bfReserved1;
  unsigned short bfReserved2;
  unsigned int bfOffBits;
} BITMAPFILEHEADER;

typedef struct
{
  unsigned int biSize;
  int biWidth;  // 宽
  int biHeight; // 高
  unsigned short biPlanes;
  unsigned short biBitCount; // 色深
  unsigned int biCompression;
  unsigned int biSizeImage;
  int biXPelsPerMeter;
  int biYPelsPerMeter;
  unsigned int biClrUsed;
  unsigned int biClrImportant;
} BITMAPINFOHEADER;

#pragma pack()

函数接口：

/****************************************************************************
 *
 * function name     :ShowBmp
 * function          : 显示图片
 * argument          
 *                      @name :bmp图片
 *                      @x ：x轴
 *                      @y ：y轴
 *
 * Return results    : none
 * note              : None
 * author            : [email protected]
 * date              : 2024-05-12
 * version           : V1.0
 * revision history  : None
 *
 ****************************************************************************/
int ShowBmp(const char *name, int x, int y)
{
  // 1.打开待显示的BMP图像  fopen
  FILE *bmp_fp = fopen("name", "rb");
  if (NULL == bmp_fp)
  {
    return -1;
  }

  // 2.读取BMP文件的图像信息，获取BMP的宽和高
  BITMAPINFOHEADER headerinfo;
  BITMAPFILEHEADER fileinfo;
  fseek(bmp_fp, 14, SEEK_SET);
  fread(&headerinfo, 1, 40, bmp_fp); // 读取40字节
  printf("bmp width = %d,height = %d\n", headerinfo.biWidth, headerinfo.biHeight);

  // 3.读取BMP图片的颜色分量
 char *bmp_buf = (char *)calloc(pic.biWidth * pic.biHeight * 3, 1);
	int offset = (4 - (pic.biWidth * 3) % 4) % 4;
	for (int i = 0; i < pic.biHeight; i++)
	{
		fread(bmp_buf + i * pic.biWidth * 3, 1, pic.biWidth * 3, bmp_fp);
		fseek(bmp_fp, offset, SEEK_CUR);
	}

  // 4.关闭BMP
  fclose(bmp_fp);

  // 5.打开LCD   open
  int lcd_fd = open("/dev/fb0", O_RDWR);
  if (-1 == bmp_fd)
  {
    printf("open %s is error\n", argv[1]);
    return -1;
  }

  // 6.对LCD进行内存映射  mmap
  int *lcd_mp = (int *)mmap(NULL, 800 * 480 * 4, PROT_READ | PROT_WRITE, MAP_SHARED, lcd_fd, 0);

  // 7.循环的把BMP图像的颜色分量依次写入到LCD的像素点中

  if (headerinfo.biHeight > 480 || headerinfo.biWidth > 800)
  {
    printf("your bmp'size over!");
  }

  int i = 0;
  int data = 0;

  for (int j = y + headerinfo.biHeight - 1; j >= y; j--)
  {
    for (int k = x; k < headerinfo.biWidth + x; ++k)
    {
      // 把BMP图片的一个像素点的颜色分量转换为LCD屏幕的一个像素点的颜色分量格式  ARGB <--- BGR
      data |= bmp_buf[i];           // B
      data |= bmp_buf[i + 1] << 8;  // G
      data |= bmp_buf[i + 2] << 16; // R

      lcd_mp[800 * j + k] = data; // BGR BGR BGR ....

      i += 3;
      data = 0;
    }
  }
  // 8.关闭LCD
  close(lcd_fd);
  munmap(lcd_mp, 800 * 480 * 4);
  free(bmp_buf)
  
  return 0;
}