【C语言】之往显存中刷入一张bmp图片数据

刺骨的言语ヽ痛彻心扉 2022-05-29 01:44 169阅读 0赞

#include <stdio.h>
    #include <unistd.h>
    #include <fcntl.h>
    #include <linux/fb.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <sys/mman.h>
    
    unsigned int rgb(unsigned char red, unsigned char green, unsigned blue);
    
    int main(int argc, char **argv)
    { 
    	int fd;
    
    	/* 打开fb设备 */
    	fd = open("/dev/fb0", O_RDWR);
    	if (fd < 0)
    	{ 
    		perror("open fb");
    		return -1;
    	}
    
    	/* 获取显存信息 */
    	struct fb_fix_screeninfo fix_info;
    	struct fb_var_screeninfo var_info;
    	int line_length;
    	int ret, x, y;
    
    	ret = ioctl(fd, FBIOGET_FSCREENINFO, &fix_info);
    	if (ret < 0)
    	{ 
    		perror("get fix_info failed");
    		close(fd);
    		return ret;
    	}
    	line_length = fix_info.line_length;
    
    	ret = ioctl(fd, FBIOGET_VSCREENINFO, &var_info);
    	if (ret < 0)
    	{ 
    		perror("get var_info failed");
    		close(fd);
    		return ret;
    	}
    	y = var_info.yres;
    	x = line_length/4;
    
    	/* fb设备内存映射 */
    	unsigned int *fb_addr;
    	
    	fb_addr = mmap(NULL, y*line_length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
    	if (MAP_FAILED == fb_addr)
    	{ 
    		perror("mmap");
    		close(fd);
    		return -2;
    	}
    
    	/* 打开bmp图片 */
    	int bmp_fd = open("./1280.bmp", O_RDONLY);
    	if (bmp_fd < 0)
    	{ 
    		perror("open bmp");
    		munmap(fb_addr, y*line_length);
    		close(fd);
    		return -3;
    	}
    
    	/* 获取bmp图片信息 */
    	struct stat bmp_stat;
    	fstat(bmp_fd, &bmp_stat);
    
    	/* bmp图片内存映射 */
    	unsigned char *bmp_addr;
    	unsigned char *tmp;
    
    	bmp_addr = mmap(NULL, bmp_stat.st_size, PROT_READ, MAP_SHARED, bmp_fd, 0);
    	if (MAP_FAILED == bmp_addr)
    	{ 
    		perror("mmap bmp");
    		munmap(fb_addr, y*line_length);
    		close(fd);
    		close(bmp_fd);
    		return -4;
    	}
    	tmp = bmp_addr + 54;  /* 跳过bmp文件头 */
    
    	/* 往显存写数据 */
    	char r, g, b;
    	int i, j;
    	
    	for (i = y-1; i >= 0; i--) /* bmp图片行数据倒叙存放 */ 
    	{ 
    		for (j = 0; j < x; j++)
    		{ 
    			r = tmp[2];
    			g = tmp[1];
    			b = tmp[0];
    			tmp += 3;
    			fb_addr[i*x+j] = rgb(r, g, b);
    		}
    	}
    
    	munmap(fb_addr, y*line_length);
    	munmap(bmp_addr, bmp_stat.st_size);
    	close(fd);
    	close(bmp_fd);
    	return 0;
    }
    
    unsigned int rgb(unsigned char red, unsigned char green, unsigned blue)
    { 
    	return (red<<16)|(green<<8)|blue;
    }