bmp。c嵌入式图像处理程序(bmp)

fbv -- simple image viewer for the linux framebuffer

Copyright (C) 2002 Tomasz Sterna

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#include "config.h"

#ifdef FBV_SUPPORT_BMP

#include "fbv.h"

#include

#include

#include

#include

#define BMP_TORASTER_OFFSET10

#define BMP_SIZE_OFFSET18

#define BMP_BPP_OFFSET28

#define BMP_RLE_OFFSET30

#define BMP_COLOR_OFFSET54

#define fill4B(a)( ( 4 - ( (a) % 4 ) ) & 0x03)

struct color {

unsigned char red;

unsigned char green;

unsigned char blue;

};

int fh_bmp_id(char *name)//读取位图头信息，判断是否为"BM"

{

int fd;

char id[2];

fd = open(name, O_RDONLY);//打开文件

if (fd == -1) {

return(0);

}

read(fd, id, 2);

close(fd);

if ( id[0]=='B' && id[1]=='M' ) {

return(1);

}

return(0);

}

void fetch_pallete(int fd, struct color pallete[], int count)//获取调色板信息

{

unsigned char buff[4];

int i;

lseek(fd, BMP_COLOR_OFFSET, SEEK_SET);//fd,28,SEEK_SET:参数28为新的读写位置

for (i=0; iread(fd, buff, 4);//将fd所指向的文件的4个字节传送给缓冲区（指针）buff所指内存中

pallete[i].red = buff[2];

pallete[i].green = buff[1];

pallete[i].blue = buff[0];

}

return;

}

int fh_bmp_load(char *name,unsigned char *buffer, unsigned char **alpha, int x,int y)

{

#if 1

int fd, bpp, raster, i, j, k, skip;

unsigned char buff[4];

unsigned char *wr_buffer = buffer + x*(y-1)*3;

struct color pallete[256];

fd = open(name, O_RDONLY);

if (fd == -1) {

return(FH_ERROR_FILE);

}

if (lseek(fd, BMP_TORASTER_OFFSET, SEEK_SET) == -1) {//从文件10处开始读写

return(FH_ERROR_FORMAT);

}

read(fd, buff, 4);

raster = buff[0] + (buff[1]<<8) + (buff[2]<<16) + (buff[3]<<24);//由上面可知：从bfOffBits

//开始四个字节：每一行扫描的字节数？

if (lseek(fd, BMP_BPP_OFFSET, SEEK_SET) == -1) {

return(FH_ERROR_FORMAT);

}

read(fd, buff, 2);

bpp = buff[0] + (buff[1]<<8);//可得biBitCount(从28开始2个字节)

switch (bpp){

case 1: /* monochrome 单色 */

skip = fill4B(x/8+(x%8?1:0));

/*#define fill4B(a)( ( 4 - ( (a) % 4 ) ) & 0x03)

1.BMP文件记录一行

图像是以字节为单位的。因此，就不存在一个字节中的数据位信息表示的点在不同的两行中。也就是说，

设显示模式位16色，在每个字节分配两个点信息时，如果图像的宽度位奇数，那么最后一个像素点的信息将独占一个字节，

这个字节的后4位将没有意义。接下来的一个字节将开始记录下一行的信息。

2.为了显示的方便，除了真彩色外，其他的每中颜色模式的行字节数要用数据“00”补齐为4的整数倍。

如果显示模式为16色，当图像宽为19时，存储时每行则要补充4-(19/2+1)%4=2个字节

（加1是因为里面有一个像素点要独占了一字节）。如果显示模式为256色，当图像宽为19时，每行也要补充4-19%4=1个字节。

*/

lseek(fd, raster, SEEK_SET);

for (i=0; ifor (j=0; jread(fd, buff, 1);

for (k=0; k<8; k++) {

if (buff[0] & 0x80) {

*wr_buffer++ = 0xff;

*wr_buffer++ = 0xff;

*wr_buffer++ = 0xff;

} else {

*wr_buffer++ = 0x00;

*wr_buffer++ = 0x00;

*wr_buffer++ = 0x00;

}

buff[0] = buff[0]<<1;

}

}

if (x%8) {

read(fd, buff, 1);

for (k=0; kif (buff[0] & 0x80) {

*wr_buffer++ = 0xff;

*wr_buffer++ = 0xff;

*wr_buffer++ = 0xff;

} else {

*wr_buffer++ = 0x00;

*wr_buffer++ = 0x00;

*wr_buffer++ = 0x00;

}

buff[0] = buff[0]<<1;

}

}

if (skip) {

read(fd, buff, skip);

}

wr_buffer -= x*6; /* backoff 2 lines - x*2 *3 */

}

break;

case 4: /* 4bit palletized */

skip = fill4B(x/2+x%2);//#define fill4B(a)( ( 4 - ( (a) % 4 ) ) & 0x03)

fetch_pallete(fd, pallete, 16);

lseek(fd, raster, SEEK_SET);

for (i=0; ifor (j=0; jread(fd, buff, 1);

buff[1] = buff[0]>>4;

buff[2] = buff[0] & 0x0f;

*wr_buffer++ = pallete[buff[1]].red;

*wr_buffer++ = pallete[buff[1]].green;

*wr_buffer++ = pallete[buff[1]].blue;

*wr_buffer++ = pallete[buff[2]].red;

*wr_buffer++ = pallete[buff[2]].green;

*wr_buffer++ = pallete[buff[2]].blue;

}

if (x%2) {

read(fd, buff, 1);

buff[1] = buff[0]>>4;

*wr_buffer++ = pallete[buff[1]].red;

*wr_buffer++ = pallete[buff[1]].green;

*wr_buffer++ = pallete[buff[1]].blue;

}

if (skip) {

read(fd, buff, skip);

}

wr_buffer -= x*6; /* backoff 2 lines - x*2 *3 */

}

break;

case 8: /* 8bit palletized */

skip = fill4B(x);

fetch_pallete(fd, pallete, 256);

lseek(fd, raster, SEEK_SET);

for (i=0; ifor (j=0; jread(fd, buff, 1);

*wr_buffer++ = pallete[buff[0]].red;

*wr_buffer++ = pallete[buff[0]].green;

*wr_buffer++ = pallete[buff[0]].blue;

}

if (skip) {

read(

fd, buff, skip);

}

wr_buffer -= x*6; /* backoff 2 lines - x*2 *3 */

}

break;

case 16: /* 16bit RGB */

return(FH_ERROR_FORMAT);

break;

case 24: /* 24bit RGB */

skip = fill4B(x*3);

lseek(fd, raster, SEEK_SET);

for (i=0; ifor (j=0; jread(fd, buff, 3);

*wr_buffer++ = buff[2];

*wr_buffer++ = buff[1];

*wr_buffer++ = buff[0];

}

if (skip) {

read(fd, buff, skip);

}

wr_buffer -= x*6; /* backoff 2 lines - x*2 *3 */

}

break;

default:

return(FH_ERROR_FORMAT);

}

close(fd);

return(FH_ERROR_OK);

#endif

}

int fh_bmp_getsize(char *name,int *x,int *y)

{

int fd;

unsigned char size[4];

fd = open(name, O_RDONLY);

if (fd == -1) {

return(FH_ERROR_FILE);//宏定义FH_ERROR_FILE 1; 见fbv.h

}

if (lseek(fd, BMP_SIZE_OFFSET, SEEK_SET) == -1) {//BMP_SIZE_OFFSET :28

return(FH_ERROR_FORMAT);//FH_ERROR_FORMAT:2

}

read(fd, size, 4);

*x = size[0] + (size[1]<<8) + (size[2]<<16) + (size[3]<<24);

//*x-=1;

read(fd, size, 4);

*y = size[0] + (size[1]<<8) + (size[2]<<16) + (size[3]<<24);

close(fd);

return(FH_ERROR_OK);

}

#endif