2.自定义函数在LCD上显示一张不超过LCD像素大小的色深为 24bit的bmp图片2024-05-12

设计程序实现在LCD上任意位置显示一张任意大小的色深为 24bit的bmp图片,要求图像不失真可以在开发板的LCD上显示。

头文件包含

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

//以1字节对齐方式对齐
#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;
//取消字节对齐
#pragma pack()

/*******************************************************************
 *
 *	函数名称:	ShowBmp
 *	函数功能:   在LCD上任意位置显示一张任意大小的色深为 24bit的bmp图片
 *	函数参数:
 *				@name 	bmp图像文件名
 *				@x		图像显示的起点x轴坐标
 *				@y		图像显示的起点y轴左边
 *				@lcd_mp	lcd屏内存映射的地址
 *	返回结果:
 * 	注意事项:   None
 * 	函数作者:   mailLinL@163.com
 *	创建日期:   2024/05/12
 *	修改历史:
 *	函数版本:	V1.0
 * *****************************************************************/
int ShowBmp(char *name, int x, int y, int *lcd_mp)
{
	// 1.打开待显示的BMP图像  fopen
	FILE *bmp_fp = fopen(name, "rb");
	if (NULL == bmp_fp)
	{
		printf("open FILE is error!\n");
		return -1;
	}
	// 2.读取BMP文件的图像信息，获取BMP的宽和高
	BITMAPINFOHEADER headinfo;
	fseek(bmp_fp, 14, SEEK_SET);
	fread(&headinfo, 1, 40, bmp_fp); // 读取40字节
	// 打开LCD   open
	int lcd_fd = open("/dev/fb0", O_RDWR);
	if (lcd_fd == -1)
	{
		printf("mmap for lcd is error\n");
		return -1;
	}
	// 调用LCD屏的像素
	struct fb_var_screeninfo lcd_vinfo;
	ioctl(lcd_fd, FBIOGET_VSCREENINFO, &lcd_vinfo);
	// 3.读取BMP图片的颜色分量
	char bmp_buf[headinfo.biWidth * headinfo.biHeight * 3];
	bzero(bmp_buf, headinfo.biWidth * headinfo.biHeight * 3);
	fread(bmp_buf, 1, headinfo.biWidth * headinfo.biHeight * 3, bmp_fp);
	printf("bmp width = %d,height = %d\n", headinfo.biWidth, headinfo.biHeight);
	// 4.关闭BMP
	fclose(bmp_fp);
	// 5.循环将bmp图像写入lcd屏指定位置
	int data = 0;
	int i = 0;
	for (int h = (y + headinfo.biHeight - 1); h >= y; h--)
	{
		for (int w = x; w < (x + headinfo.biWidth); w++)
		{
			data |= bmp_buf[i];
			data |= bmp_buf[i + 1] << 8;
			data |= bmp_buf[i + 2] << 16;
			lcd_mp[h * (lcd_vinfo.xres) + w] = data;
			i += 3;
			data = 0;
		}
	}
	// 关闭LCD
	close(lcd_fd);
	munmap(lcd_mp, lcd_vinfo.xres * lcd_vinfo.yres * 4);
	return 0;
}

int main(int argc, char *argv[])
{
	if (argc != 2)
	{
		printf("argument is error!\n");
		return -1;
	}
	if (NULL == argv[1])
	{
		printf("argument 2 is error!\n");
		return -1;
	}
	// 打开LCD   open
	int lcd_fd = open("/dev/fb0", O_RDWR);
	if (lcd_fd == -1)
	{
		printf("mmap for lcd is error\n");
		return -1;
	}
	// 调用LCD屏的像素
	struct fb_var_screeninfo lcd_vinfo;
	ioctl(lcd_fd, FBIOGET_VSCREENINFO, &lcd_vinfo);
	// 对LCD进行内存映射  mmap
	int *lcd_mp = (int *)mmap(NULL,
							  lcd_vinfo.xres * lcd_vinfo.yres * 4,
							  PROT_READ | PROT_WRITE,
							  MAP_SHARED,
							  lcd_fd,
							  0);
	// 键盘输入图片显示的起始位置
	int x, y;
	scanf("%d%d", &x, &y);
	ShowBmp(argv[1], x, y, lcd_mp);
	// 关闭LCD
	munmap(lcd_mp, lcd_vinfo.xres * lcd_vinfo.yres * 4);
	close(lcd_fd);
	return 0;
}