有哪位老兄做过PPM文件的读写？

[Previewer]

我要做个PPM文件的解析，此PPM文件存储的时一个表格，要把单元格里的内容提取出来。
全是2进制的，没一点头绪，哪位老兄给些提示，必高分答谢！：）

[Previewer]

没有人可以给些提示吗？

[djfu]

这个你必须了解原始PPM 文件是怎么序列化的以及它的数据结构存储方式，否则真是半点头绪都没有。

[Previewer]

没做过图像的，PPM文件没有一种标准格式码？可以自己定义？

[qiansen]

/*pnmfile.h */

#ifndef PNM_FILE_H
#define PNM_FILE_H

#include <cstdlib>
#include <climits>
#include <cstring>
#include <fstream>
#include "image.h"
#include "misc.h"
#include <iostream.h>//for debug,qiansen

#define BUF_SIZE 256

class pnm_error { };

static void read_packed(unsigned char *data, int size, std::ifstream &f) {
unsigned char c = 0;

int bitshift = -1;
for (int pos = 0; pos < size; pos++) {
if (bitshift == -1) {
c = f.get();
bitshift = 7;
}
data[pos] = (c >> bitshift) & 1;
bitshift--;
}
}

static void write_packed(unsigned char *data, int size, std::ofstream &f) {
unsigned char c = 0;

int bitshift = 7;
for (int pos = 0; pos < size; pos++) {
c = c | (data[pos] << bitshift);
bitshift--;
if ((bitshift == -1) || (pos == size-1)) {
f.put(c);
bitshift = 7;
c = 0;
}
}
}

/* read PNM field, skipping comments */
static void pnm_read(std::ifstream &file, char *buf) {
char doc[BUF_SIZE];
char c;

file >> c;
while (c == '#') {
file.getline(doc, BUF_SIZE);
file >> c;
}
file.putback(c);

file.width(BUF_SIZE);
file >> buf;
file.ignore();
}

static image<uchar> *loadPBM(const char *name) {
char buf[BUF_SIZE];

/* read header */
std::ifstream file(name, std::ios::in | std::ios::binary);
pnm_read(file, buf);
if (strncmp(buf, "P4", 2))
throw pnm_error();

pnm_read(file, buf);
int width = atoi(buf);
pnm_read(file, buf);
int height = atoi(buf);

/* read data */
image<uchar> *im = new image<uchar>(width, height);
for (int i = 0; i < height; i++)
read_packed(imPtr(im, 0, i), width, file);

return im;
}

static void savePBM(image<uchar> *im, const char *name) {
int width = im->width();
int height = im->height();
std::ofstream file(name, std::ios::out | std::ios::binary);

file << "P4\n" << width << " " << height << "\n";
for (int i = 0; i < height; i++)
write_packed(imPtr(im, 0, i), width, file);
}

static image<uchar> *loadPGM(const char *name) {
char buf[BUF_SIZE];

/* read header */
std::ifstream file(name, std::ios::in | std::ios::binary);
pnm_read(file, buf);
if (strncmp(buf, "P5", 2))
throw pnm_error();

pnm_read(file, buf);
int width = atoi(buf);
pnm_read(file, buf);
int height = atoi(buf);

pnm_read(file, buf);
if (atoi(buf) > UCHAR_MAX)
throw pnm_error();

/* read data */
image<uchar> *im = new image<uchar>(width, height);
file.read((char *)imPtr(im, 0, 0), width * height * sizeof(uchar));

return im;
}

static void savePGM(image<uchar> *im, const char *name) {
int width = im->width();
int height = im->height();
std::ofstream file(name, std::ios::out | std::ios::binary);

file << "P5\n" << width << " " << height << "\n" << UCHAR_MAX << "\n";
file.write((char *)imPtr(im, 0, 0), width * height * sizeof(uchar));
}

static image<rgb> *loadPPM(const char *name) {
char buf[BUF_SIZE], doc[BUF_SIZE];

/* read header */
std::ifstream file(name, std::ios::in | std::ios::binary);
pnm_read(file, buf);
if (strncmp(buf, "P5", 2)){
//throw pnm_error();
cout<<"pnm version is P6,may be not supported."<<endl;
}
pnm_read(file, buf);
int width = atoi(buf);
pnm_read(file, buf);
int height = atoi(buf);

pnm_read(file, buf);
if (atoi(buf) > UCHAR_MAX)
throw pnm_error();

/* read data */
image<rgb> *im = new image<rgb>(width, height);
file.read((char *)imPtr(im, 0, 0), width * height * sizeof(rgb));

return im;
}

static void savePPM(image<rgb> *im, const char *name) {
int width = im->width();
int height = im->height();
std::ofstream file(name, std::ios::out | std::ios::binary);

file << "P6\n" << width << " " << height << "\n" << UCHAR_MAX << "\n";
file.write((char *)imPtr(im, 0, 0), width * height * sizeof(rgb));
}

template <class T>
void load_image(image<T> **im, const char *name) {
char buf[BUF_SIZE];

/* read header */
std::ifstream file(name, std::ios::in | std::ios::binary);
pnm_read(file, buf);
if (strncmp(buf, "VLIB", 9))
throw pnm_error();

pnm_read(file, buf);
int width = atoi(buf);
pnm_read(file, buf);
int height = atoi(buf);

/* read data */
*im = new image<T>(width, height);
file.read((char *)imPtr((*im), 0, 0), width * height * sizeof(T));
}

template <class T>
void save_image(image<T> *im, const char *name) {
int width = im->width();
int height = im->height();
std::ofstream file(name, std::ios::out | std::ios::binary);

file << "VLIB\n" << width << " " << height << "\n";
file.write((char *)imPtr(im, 0, 0), width * height * sizeof(T));
}

#endif

[qiansen]

/* a simple image class
filename: image.h */

#ifndef IMAGE_H
#define IMAGE_H

#include <cstring>

template <class T>
class image {
public:
/* create an image */
image(const int width, const int height, const bool init = true);

/* delete an image */
~image();

/* init an image */
void init(const T &val);

/* copy an image */
image<T> *copy() const;

/* get the width of an image. */
int width() const { return w; }

/* get the height of an image. */
int height() const { return h; }

/* image data. */
T *data;

/* row pointers. */
T **access;

private:
int w, h;
};

/* use imRef to access image data. */
#define imRef(im, x, y) (im->access[y][x])

/* use imPtr to get pointer to image data. */
#define imPtr(im, x, y) &(im->access[y][x])

template <class T>
image<T>::image(const int width, const int height, const bool init) {
w = width;
h = height;
data = new T[w * h]; // allocate space for image data
access = new T*[h]; // allocate space for row pointers

// initialize row pointers
for (int i = 0; i < h; i++)
access[i] = data + (i * w);

if (init)
memset(data, 0, w * h * sizeof(T));
}

template <class T>
image<T>::~image() {
delete [] data;
delete [] access;
}

template <class T>
void image<T>::init(const T &val) {
T *ptr = imPtr(this, 0, 0);
T *end = imPtr(this, w-1, h-1);
while (ptr <= end)
*ptr++ = val;
}


template <class T>
image<T> *image<T>::copy() const {
image<T> *im = new image<T>(w, h, false);
memcpy(im->data, data, w * h * sizeof(T));
return im;
}

#endif

[qiansen]

建议你搜索一下linux下的图像处理包，大部分都有关于ppm格式的读写的代码的。

[Previewer]

谢谢 十里平湖