我有两个文件，我需要使用它。 bmplib.h ...
#ifndef BMPLIB_H
#define BMPLIB_H
typedef struct {
unsigned short padding;
unsigned short bfType;
unsigned int bfSize;
unsigned short bfReserved1;
unsigned short bfReserved2;
unsigned int bfOffBits;
} BITMAPFILEHEADER;
typedef struct {
unsigned int biSize;
int biWidth;
int biHeight;
unsigned short biPlanes;
unsigned short biBitCount;
unsigned int biCompression;
unsigned int biSizeImage;
unsigned int biXPelsPerMeter;
unsigned int biYPelsPerMeter;
unsigned int biClrUsed;
unsigned int biClrImportant;
} BITMAPINFOHEADER;
typedef struct {
unsigned char r;
unsigned char g;
unsigned char b;
} PIXEL;
#define DEFAULT_BITMAP_OFFSET 1078
/* Read an uncompressed 24-bit bmp from a file named 'filename' (if
null, it's standard input); return the number of 'rows', the number
of 'cols', and the 'bitmap' as an array of PIXELs. The function
return 0 if successful. */
int readFile (char* filename, int* rows, int* cols, PIXEL** bitmap);
/* Write an uncompressed 24-bit bmp to a file named 'filename' (if
null, it's standard output); the dimension of the bmp is the number
of 'rows' by the number of 'cols', and the 'bitmap' contains an
array of PIXELs. The function return 0 if successful. */
int writeFile (char* filename, int rows, int cols, PIXEL* bitmap);
/* Read bmp file header from file 'fd', return the number of 'rows',
the number of 'cols', and the 'start' position of the bitmap. The
function returns 0 if successful. */
int readHeader(int fd, int *rows, int *cols, unsigned int *start);
/* Write bmp file header to file 'fd'; the dimention of the bitmap is
the number of 'rows' by the number of 'cols', and it starts at the
'start' position. The function returns 0 if successful. */
int writeHeader(int fd, int rows, int cols, unsigned int start);
/* Read the 'bitmap' from file 'fd'; the dimention of the bitmap is
the number of 'rows' by the number of 'cols', and it starts at the
'start' position. The function returns 0 if successful. */
int readBits(int fd, PIXEL* bitmap, int rows, int cols, unsigned int start);
/* Write the 'bitmap' to file 'fd'; the dimention of the bitmap is the
number of 'rows' by the number of 'cols', and it starts at the
'start' position. The function returns 0 if successful. */
int writeBits(int fd, int rows, int cols, PIXEL* bitmap, unsigned int start);
#endif /*BMPLIB_H*/
和bmplib.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include "bmplib.h"
static int myread(int fd, char* buf, unsigned int size)
{
int r = 0;
while(r < size) {
int x = read(fd, &buf[r], size-r);
if(x < 0) return x;
else r += x;
}
return size;
}
static int mywrite(int fd, char* buf, unsigned int size)
{
int w = 0;
while(w < size) {
int x = write(fd, &buf[w], size-w);
if(x < 0) return x;
else w += x;
}
return size;
}
int readFile (char *filename, int *rows, int *cols, PIXEL** bitmap)
{
int fd, ret;
unsigned int start;
if(filename) {
if((fd = open(filename, O_RDONLY)) < 0) {
perror("Can't open bmp file to read");
return -1;
}
} else fd = STDIN_FILENO;
ret = readHeader (fd, rows, cols, &start);
if(ret) return ret;
*bitmap = (PIXEL*)malloc(sizeof(PIXEL)*(*rows)*(*cols));
ret = readBits (fd, *bitmap, *rows, *cols, start);
if(ret) return ret;
if(filename) close(fd);
return 0;
}
int writeFile (char* filename, int rows, int cols, PIXEL* bitmap)
{
int fd, ret;
unsigned int start = DEFAULT_BITMAP_OFFSET;
if(filename) {
if((fd = open(filename, O_RDWR|O_CREAT|O_TRUNC, 0666)) < 0) {
perror("Can't open bmp file to write");
return -1;
}
} else fd = STDOUT_FILENO;
ret = writeHeader (fd, rows, cols, start);
if(ret) return ret;
ret = writeBits(fd, rows, cols, bitmap, start);
if(ret) return ret;
if(filename) close(fd);
return 0;
}
int readHeader(int fd, int *rows, int *cols, unsigned int *start)
{
BITMAPFILEHEADER bmfh;
BITMAPINFOHEADER bmih;
if(myread(fd, ((char*)&bmfh)+2, sizeof(bmfh)-2) <= 0) {
perror("Can't read BITMAPFILEHEADER");
return -2;
}
if(myread(fd, (char*)&bmih, sizeof(bmih)) <= 0) {
perror("Can't read BITMAPINFOHEADER");
return -3;
}
if(bmih.biCompression != 0) {
fprintf(stderr, "Can't read compressed bmp");
return -4;
}
if(bmih.biBitCount != 24) {
fprintf(stderr, "Can't handle bmp other than 24-bit");
return -5;
}
*rows = bmih.biHeight;
*cols = bmih.biWidth;
*start = bmfh.bfOffBits;
return 0;
}
int writeHeader(int fd, int rows, int cols, unsigned int start)
{
unsigned int fileSize;
unsigned int headerSize;
unsigned int paddedCols;
BITMAPFILEHEADER bmfh;
BITMAPINFOHEADER bmih;
memset (&bmfh, 0, sizeof(bmfh));
memset (&bmih, 0, sizeof(bmih));
paddedCols = ((cols/4)*4 !=cols ? ((cols+4)/4)*4 : cols);
headerSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
fileSize = rows*paddedCols*sizeof(PIXEL)+headerSize;
bmfh.bfType = 0x4D42;
bmfh.bfSize = fileSize;
bmfh.bfReserved1 = 0;
bmfh.bfReserved2 = 0;
bmfh.bfOffBits = start;
bmih.biSize = 40;
bmih.biWidth = cols;
bmih.biHeight = rows;
bmih.biPlanes = 1;
bmih.biBitCount = 24;
bmih.biCompression = 0;
bmih.biSizeImage = 0;
bmih.biXPelsPerMeter = 0;
bmih.biYPelsPerMeter = 0;
bmih.biClrUsed = 0;
bmih.biClrImportant = 0;
if(mywrite(fd, ((char*)&bmfh)+2, sizeof(bmfh)-2) < 0) {
perror("Can't write BITMAPFILEHEADER");
return -2;
}
if(mywrite(fd, (char*)&bmih, sizeof(bmih)) < 0) {
perror("Can't write BITMAPINFOHEADER");
return -3;
}
return 0;
}
int readBits(int fd, PIXEL* bitmap, int rows, int cols, unsigned int start)
{
int row;
char padding[3];
int padAmount;
char useless[DEFAULT_BITMAP_OFFSET];
padAmount = ((cols * sizeof(PIXEL)) % 4) ? (4 - ((cols * sizeof(PIXEL)) % 4)) : 0;
start -= sizeof(BITMAPFILEHEADER)-2+sizeof(BITMAPINFOHEADER);
if(start > 0 && myread(fd, useless, start) < 0) {
perror("Can't lseek to bitmap");
return -6;
}
/*
if(lseek (fd, start, SEEK_SET) < 0) {
perror("Can't lseek to bitmap");
return -6;
}
*/
for (row=0; row < rows; row++) {
if(myread(fd, (char*)(bitmap+(row*cols)), cols*sizeof(PIXEL)) < 0) {
perror("Can't read bitmap");
return -7;
}
if(padAmount > 0) {
if(myread(fd, padding, padAmount) < 0) {
perror("Can't read bitmap");
return -8;
}
}
}
return 0;
}
int writeBits(int fd, int rows, int cols, PIXEL* bitmap, unsigned int start)
{
int row;
char padding[3];
int padAmount;
char useless[DEFAULT_BITMAP_OFFSET];
padAmount = ((cols * sizeof(PIXEL)) % 4) ? (4 - ((cols * sizeof(PIXEL)) % 4)) : 0;
memset(padding, 0, 3);
start -= sizeof(BITMAPFILEHEADER)-2+sizeof(BITMAPINFOHEADER);
if(start > 0) {
memset(useless, 0, start);
if(mywrite(fd, useless, start) < 0) {
perror("Can't lseek to bitmap");
return -6;
}
}
/*
if(lseek (fd, start, SEEK_SET) < 0) {
perror("Can't lseek to bitmap");
return -6;
}
*/
for (row=0; row < rows; row++) {
if(mywrite(fd, (char*)(bitmap+(row*cols)), cols*sizeof(PIXEL)) < 0) {
perror("Can't write bitmap");
return -7;
}
if(padAmount > 0) {
if(mywrite(fd, padding, padAmount) < 0) {
perror("Can't write bitmap");
return -8;
}
}
}
return 0;
}
我试图理解如何使用readInput函数加载位图图像，但我完全不知道我需要为行，列和PIXEL数组传递什么参数。此外，我不太明白我是如何使用这个库来操作位图的;放大或翻转90度。有人可以解释这段代码是如何工作的，特别是如何使用下面的函数成功加载位图图像，然后放大或翻转它。