通過fb0顯示圖片

代碼

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <errno.h>

//14byte文件頭
typedef struct
{
	char cfType[2];  //文件類型，"BM"(0x4D42)
	int  cfSize;     //文件大小（字節）
	int  cfReserved; //保留，值爲0
	int  cfoffBits;  //數據區相對於文件頭的偏移量（字節）
}__attribute__((packed)) BITMAPFILEHEADER;
//__attribute__((packed))的作用是告訴編譯器取消結構在編譯過程中的優化對齊

//40byte信息頭
typedef struct
{
	char ciSize[4];          //BITMAPFILEHEADER所佔的字節數
	int  ciWidth;            //寬度
	int  ciHeight;           //高度
	char ciPlanes[2];        //目標設備的位平面數，值爲1
	int  ciBitCount;         //每個像素的位數
	char ciCompress[4];      //壓縮說明
	char ciSizeImage[4];     //用字節表示的圖像大小，該數據必須是4的倍數
	char ciXPelsPerMeter[4]; //目標設備的水平像素數/米
	char ciYPelsPerMeter[4]; //目標設備的垂直像素數/米
	char ciClrUsed[4];       //位圖使用調色板的顏色數
	char ciClrImportant[4];  //指定重要的顏色數，當該域的值等於顏色數時（或者等於0時），表示所有顏色都一樣重要
}__attribute__((packed)) BITMAPINFOHEADER;

typedef struct
{
	unsigned char blue;
	unsigned char green;
	unsigned char red;
	unsigned char reserved;
}__attribute__((packed)) PIXEL; //顏色模式RGB



typedef struct
{
	int          fbfd;
	char         *fbp;
	unsigned int xres;
	unsigned int yres;
	unsigned int xres_virtual;
	unsigned int yres_virtual;
	unsigned int xoffset;
	unsigned int yoffset;
	unsigned int bpp;
	unsigned long line_length;
	unsigned long size;

	struct fb_bitfield red;
	struct fb_bitfield green;
	struct fb_bitfield blue;
} FB_INFO;

typedef struct
{
	unsigned int width;
	unsigned int height;
	unsigned int bpp;
	unsigned long size;
	unsigned int data_offset;
} IMG_INFO;



FB_INFO fb_info;
IMG_INFO img_info;

int show_bmp(char *img_name);

static int cursor_bitmap_format_convert(char *dst,char *src, unsigned long img_len_one_line)
{
	int img_len ,fb_len ;
	char *p;
	__u32 val;
	PIXEL pix;

	p = (char *)&val;

	img_len = img_info.width; /*一行圖片的長度*/
	fb_len = fb_info.xres; /*一行顯示屏的長度*/

	/*進行x軸的偏移*/
	dst += fb_info.xoffset * (fb_info.bpp / 8);
	fb_len -= fb_info.xoffset;

	/*bmp 數據是上下左右顛倒的，這裏只進行左右的處理*/
	/*先定位到圖片的最後一個像素的地址，然後往第一個像素的方向處理，進行左右顛倒的處理*/
	src += img_len_one_line - 1;

	/*處理一行要顯示的數據*/
	while(1) {
		if (img_info.bpp == 32)
			pix.reserved = *(src--);
		pix.red   = *(src--);
		pix.green = *(src--);
		pix.blue  = *(src--);

		val = 0x00;
		val |= (pix.red >> (8 - fb_info.red.length)) << fb_info.red.offset;
		val |= (pix.green >> (8 - fb_info.green.length)) << fb_info.green.offset;
		val |= (pix.blue >> (8 - fb_info.blue.length)) << fb_info.blue.offset;


		if (fb_info.bpp == 16) {
			*(dst++) = *(p + 0);
			*(dst++) = *(p + 1);
		}
		else if (fb_info.bpp == 24) {
			*(dst++) = *(p + 0);
			*(dst++) = *(p + 1);
			*(dst++) = *(p + 2);
		}
		else if (fb_info.bpp == 32) {
			*(dst++) = *(p + 0);
			*(dst++) = *(p + 1);
			*(dst++) = *(p + 2);
			*(dst++) = *(p + 3);
		}

		/*超過圖片長度或顯示屏長度認爲一行處理完了*/
		img_len--;
		fb_len--;
		if (img_len <= 0 || fb_len <= 0)
			break;
	}
#if 0
	printf("r = %d\n", pix.red);
	printf("g = %d\n", pix.green);
	printf("b = %d\n", pix.blue);
#endif
	return 0;
}

int show_bmp(char *img_name)
{

	FILE *fp;
	int ret = 0;
	BITMAPFILEHEADER FileHead;
	BITMAPINFOHEADER InfoHead;

	if(img_name == NULL) {
		printf("img_name is null\n");
		return -1;
	}

	fp = fopen( img_name, "rb" );
	if(fp == NULL) {
		printf("img[%s] open failed\n", img_name);
		ret = -1;
		goto err_showbmp;
	}

	/* 移位到文件頭部 */
	fseek(fp, 0, SEEK_SET);

	ret = fread(&FileHead, sizeof(BITMAPFILEHEADER), 1, fp);
	if ( ret != 1) {
		printf("img read failed\n");
		ret = -1;
		goto err_showbmp;
	}

	//檢測是否是bmp圖像
	if (memcmp(FileHead.cfType, "BM", 2) != 0) {
		printf("it's not a BMP file[%c%c]\n", FileHead.cfType[0], FileHead.cfType[1]);
		ret = -1;
		goto err_showbmp;
	}

	ret = fread( (char *)&InfoHead, sizeof(BITMAPINFOHEADER),1, fp );
	if ( ret != 1) {
		printf("read infoheader error!\n");
		ret = -1;
		goto err_showbmp;
	}

	img_info.width       = InfoHead.ciWidth;
	img_info.height      = InfoHead.ciHeight;
	img_info.bpp         = InfoHead.ciBitCount;
	img_info.size        = FileHead.cfSize;
	img_info.data_offset = FileHead.cfoffBits;

	printf("img info w[%d] h[%d] bpp[%d] size[%ld] offset[%d]\n", img_info.width, img_info.height, img_info.bpp, img_info.size, img_info.data_offset);

	if (img_info.bpp != 24 && img_info.bpp != 32) {
		printf("img bpp is not 24 or 32\n");
		ret = -1;
		goto err_showbmp;
	}


	/*
	 *一行行處理
	 */
	char *buf_img_one_line;
	char *buf_fb_one_line;
	char *p;
	int fb_height;

	long img_len_one_line = img_info.width * (img_info.bpp / 8);
	long fb_len_one_line = fb_info.line_length;

	printf("img_len_one_line = %d\n", img_len_one_line);
	printf("fb_len_one_line = %d\n", fb_info.line_length);

	buf_img_one_line = (char *)calloc(1, img_len_one_line + 256);
	if(buf_img_one_line == NULL) {
		printf("alloc failed\n");
		ret = -1;
		goto err_showbmp;
	}

	buf_fb_one_line = (char *)calloc(1, fb_len_one_line + 256);
	if(buf_fb_one_line == NULL) {
		printf("alloc failed\n");
		ret = -1;
		goto err_showbmp;
	}


	fseek(fp, img_info.data_offset, SEEK_SET);

	p = fb_info.fbp + fb_info.yoffset * fb_info.line_length; /*進行y軸的偏移*/
	fb_height = fb_info.yres;
	while (1) {
		memset(buf_img_one_line, 0, img_len_one_line);
		memset(buf_fb_one_line, 0, fb_len_one_line);
		ret = fread(buf_img_one_line, 1, img_len_one_line, fp);
		if (ret < img_len_one_line) {
			/*圖片讀取完成，則圖片顯示完成*/
			printf("read to end of img file\n");
			cursor_bitmap_format_convert(buf_fb_one_line, buf_img_one_line, img_len_one_line); /*數據轉換*/
			memcpy(fb_info.fbp, buf_fb_one_line, fb_len_one_line);
			break;
		}

		cursor_bitmap_format_convert(buf_fb_one_line, buf_img_one_line, img_len_one_line); /*數據轉換*/
		memcpy(p, buf_fb_one_line, fb_len_one_line); /*顯示一行*/
		p += fb_len_one_line;

		/*超過顯示屏寬度認爲圖片顯示完成*/
		fb_height--;
		if (fb_height <= 0)
			break;
	}

	free(buf_img_one_line);
	free(buf_fb_one_line);

	fclose(fp);
	return ret;
err_showbmp:
	if (fp)
		fclose(fp);
	return ret;
}

int show_picture(char *img_name)
{
	struct fb_var_screeninfo vinfo;
	struct fb_fix_screeninfo finfo;

	if (fb_info.fbfd <= -1) {
		printf("fb open fialed\n");
		return -1;
	}

	if (ioctl(fb_info.fbfd, FBIOGET_FSCREENINFO, &finfo)) {
		printf("fb ioctl fialed\n");
		return -1;
	}

	if (ioctl(fb_info.fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
		printf("fb ioctl fialed\n");
		return -1;
	}

	fb_info.xres = vinfo.xres;
	fb_info.yres = vinfo.yres;
	fb_info.xres_virtual = vinfo.xres_virtual;
	fb_info.yres_virtual = vinfo.yres_virtual;
	fb_info.xoffset = vinfo.xoffset;
	fb_info.yoffset = vinfo.yoffset;
	fb_info.bpp  = vinfo.bits_per_pixel;
	fb_info.line_length = finfo.line_length;
	fb_info.size = finfo.smem_len;

	memcpy(&fb_info.red, &vinfo.red, sizeof(struct fb_bitfield));
	memcpy(&fb_info.green, &vinfo.green, sizeof(struct fb_bitfield));
	memcpy(&fb_info.blue, &vinfo.blue, sizeof(struct fb_bitfield));

	printf("fb info x[%d] y[%d] x_v[%d] y_v[%d] xoffset[%d] yoffset[%d] bpp[%d] line_length[%ld] size[%ld]\n", fb_info.xres, fb_info.yres, fb_info.xres_virtual, fb_info.yres_virtual, fb_info.xoffset, fb_info.yoffset, fb_info.bpp, fb_info.line_length, fb_info.size);

	printf("fb info red off[%d] len[%d] msb[%d]\n", fb_info.red.offset, fb_info.red.length, fb_info.red.msb_right);
	printf("fb info green off[%d] len[%d] msb[%d]\n", fb_info.green.offset, fb_info.green.length, fb_info.green.msb_right);
	printf("fb info blue off[%d] len[%d] msb[%d]\n", fb_info.blue.offset, fb_info.blue.length, fb_info.blue.msb_right);

	if (fb_info.bpp != 16 && fb_info.bpp != 24 && fb_info.bpp != 32) {
		printf("fb bpp is not 16,24 or 32\n");
		return -1;
	}

	if (fb_info.red.length > 8 || fb_info.green.length > 8 || fb_info.blue.length > 8) {
		printf("fb red|green|blue length is invalid\n");
		return -1;
	}

	// 內存映射
	fb_info.fbp = (char *)mmap(0, fb_info.size, PROT_READ | PROT_WRITE, MAP_SHARED, fb_info.fbfd, 0);
	if (fb_info.fbp == (char *)-1) {
		printf("mmap fialed\n");
		return -1;
	}

	show_bmp(img_name);

	//刪除映射
	munmap(fb_info.fbp, fb_info.size);

	return 0;
}


int main(int argc, char **argv)
{
	char img_name[64];

	if (argc != 2) {
		printf("arg error\n");
		return 0;
	}

	snprintf(img_name, sizeof(img_name), "%s", argv[1]);
	printf("img_name = %s\n", img_name);

	fb_info.fbfd = open("/dev/fb0", O_RDWR);
	if (!fb_info.fbfd) {
		printf("Error: cannot open framebuffer device(/dev/fb0).\n");
		return -1;
	}
	show_picture(img_name);

	close(fb_info.fbfd);
		return 0;
}

運行情況

圖號	分辨率	位深度	顯示情況
1	658*986	24	灰色半個
2	1024*600	24	正常
3	1024*600	32	正常
4	658*986	32	正常 半個

圖片

如果需要，去下面鏈接下載：
https://download.csdn.net/download/qichongjin/12326281
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