OpenCV：如何阅读.pfm文件？

Question

有没有办法在OpenCV中读取.pfm文件？

非常感谢您的任何建议！

Answer 1

“file formate（见http://netpbm.sourceforge.net/doc/pfm.html），我写了下面的读/写函数，它们只依赖于标准的C/C++库。在读取/写入pfm文件（如MiddleBury Computer Vision的ground truth disparity“.pfm”文件（见http://vision.middlebury.edu/stereo/submit3/））时，它证明可以很好地工作。

#ifndef _PGM_H_ 
#define _PGM_H_ 
#include <fstream> 
#include <iostream> 
#include <algorithm> 
#include <string> 
#include <cstdint> 
#include <cstdlib> 
#include <cstring> 
#include <bitset>　/*std::bitset<32>*/ 
#include <cstdio> 

enum PFM_endianness { BIG, LITTLE, ERROR}; 

class PFM { 
public: 
    PFM(); 
    inline bool is_little_big_endianness_swap(){ 
     if (this->endianess == 0.f) { 
      std::cerr << "this-> endianness is not assigned yet!\n"; 
      exit(0); 
     } 
     else { 
      uint32_t endianness = 0xdeadbeef; 
      //std::cout << "\n" << std::bitset<32>(endianness) << std::endl; 
      unsigned char * temp = (unsigned char *)&endianness; 
      //std::cout << std::bitset<8>(*temp) << std::endl; 
      PFM_endianness endianType_ = ((*temp)^0xef == 0 ? 
       LITTLE : (*temp)^(0xde) == 0 ? BIG : ERROR); 
      // ".pfm" format file specifies that: 
      // positive scale means big endianess; 
      // negative scale means little endianess. 
      return ((BIG == endianType_) && (this->endianess < 0.f)) 
       || ((LITTLE == endianType_) && (this->endianess > 0.f)); 
     } 
    } 


    template<typename T> 
    T * read_pfm(const std::string & filename) { 
     FILE * pFile; 
     pFile = fopen(filename.c_str(), "rb"); 
     char c[100]; 
     if (pFile != NULL) { 
      fscanf(pFile, "%s", c); 
      // strcmp() returns 0 if they are equal. 
      if (!strcmp(c, "Pf")) { 
       fscanf(pFile, "%s", c); 
       // atoi: ASCII to integer. 
       // itoa: integer to ASCII. 
       this->width = atoi(c); 
       fscanf(pFile, "%s", c); 
       this->height = atoi(c); 
       int length_ = this->width * this->height; 
       fscanf(pFile, "%s", c); 
       this->endianess = atof(c); 

       fseek(pFile, 0, SEEK_END); 
       long lSize = ftell(pFile); 
       long pos = lSize - this->width*this->height * sizeof(T); 
       fseek(pFile, pos, SEEK_SET); 

       T* img = new T[length_]; 
       //cout << "sizeof(T) = " << sizeof(T); 
       fread(img, sizeof(T), length_, pFile); 
       fclose(pFile); 

       /* The raster is a sequence of pixels, packed one after another, 
       * with no delimiters of any kind. They are grouped by row, 
       * with the pixels in each row ordered left to right and 
       * the rows ordered bottom to top. 
       */ 
       T* tbimg = (T *)malloc(length_ * sizeof(T));// top-to-bottom. 
       //PFM SPEC image stored bottom -> top reversing image           
       for (int i = 0; i < this->height; i++) { 
        memcpy(&tbimg[(this->height - i - 1)*(this->width)], 
         &img[(i*(this->width))], 
         (this->width) * sizeof(T)); 
       } 


       if (this->is_little_big_endianness_swap()){ 
        std::cout << "little-big endianness transformation is needed.\n"; 
        // little-big endianness transformation is needed. 
        union { 
         T f; 
         unsigned char u8[sizeof(T)]; 
        } source, dest; 

        for (int i = 0; i < length_; ++i) { 
         source.f = tbimg[i]; 
         for (unsigned int k = 0, s_T = sizeof(T); k < s_T; k++) 
          dest.u8[k] = source.u8[s_T - k - 1]; 
         tbimg[i] = dest.f; 
         //cout << dest.f << ", "; 
        } 
       } 
       delete[] img; 
       return tbimg; 

      } 
      else { 
       std::cout << "Invalid magic number!" 
        << " No Pf (meaning grayscale pfm) is missing!!\n"; 
       fclose(pFile); 
       exit(0); 
      } 

     } 
     else { 
      std::cout << "Cannot open file " << filename 
       << ", or it does not exist!\n"; 
      fclose(pFile); 
      exit(0); 
     } 

    } 

    template<typename T> 
    void write_pfm(const std::string & filename, const T* imgbuffer, 
     const float & endianess_) { 
     std::ofstream ofs(filename.c_str(), std::ifstream::binary); 
     // ** 1) Identifier Line: The identifier line contains the characters 
     // "PF" or "Pf". PF means it's a color PFM. 
     // Pf means it's a grayscale PFM. 
     // ** 2) Dimensions Line: 
     // The dimensions line contains two positive decimal integers, 
     // separated by a blank. The first is the width of the image; 
     // the second is the height. Both are in pixels. 
     // ** 3) Scale Factor/Endianness: 
     // The Scale Factor/Endianness line is a queer line that jams 
     // endianness information into an otherwise sane description 
     // of a scale. The line consists of a nonzero decimal number, 
     // not necessarily an integer. If the number is negative, that 
     // means the PFM raster is little endian. Otherwise, it is big 
     // endian. The absolute value of the number is the scale 
     // factor for the image. 
     // The scale factor tells the units of the samples in the raster. 
     // You use somehow it along with some separately understood unit 
     // information to turn a sample value into something meaningful, 
     // such as watts per square meter. 

     ofs << "Pf\n" 
      << this->width << " " << this->height << "\n" 
      << endianess_ << "\n"; 
     /* PFM raster: 
     * The raster is a sequence of pixels, packed one after another, 
     * with no delimiters of any kind. They are grouped by row, 
     * with the pixels in each row ordered left to right and 
     * the rows ordered bottom to top. 
     * Each pixel consists of 1 or 3 samples, packed one after another, 
     * with no delimiters of any kind. 1 sample for a grayscale PFM 
     * and 3 for a color PFM (see the Identifier Line of the PFM header). 
     * Each sample consists of 4 consecutive bytes. The bytes represent 
     * a 32 bit string, in either big endian or little endian format, 
     * as determined by the Scale Factor/Endianness line of the PFM 
     * header. That string is an IEEE 32 bit floating point number code. 
     * Since that's the same format that most CPUs and compiler use, 
     * you can usually just make a program use the bytes directly 
     * as a floating point number, after taking care of the 
     * endianness variation. 
     */ 
     int length_ = this->width*this->height; 
     this->endianess = endianess_; 
     T* tbimg = (T *)malloc(length_ * sizeof(T)); 
     // PFM SPEC image stored bottom -> top reversing image 
     for (int i = 0; i < this->height; i++) { 
      memcpy(&tbimg[(this->height - i - 1)*this->width], 
       &imgbuffer[(i*this->width)], 
       this->width * sizeof(T)); 
     } 

     if (this->is_little_big_endianness_swap()) { 
      std::cout << "little-big endianness transformation is needed.\n"; 
      // little-big endianness transformation is needed. 
      union { 
       T f; 
       unsigned char u8[sizeof(T)]; 
      } source, dest; 

      for (int i = 0; i < length_; ++i) { 
       source.f = tbimg[i]; 
       for (size_t k = 0, s_T = sizeof(T); k < s_T; k++) 
        dest.u8[k] = source.u8[s_T - k - 1]; 
       tbimg[i] = dest.f; 
       //cout << dest.f << ", "; 
      } 
     } 

     ofs.write((char *)tbimg, this->width*this->height * sizeof(T)); 
     ofs.close(); 
     free(tbimg); 
    } 

    inline float getEndianess(){return endianess;} 
    inline int getHeight(void){return height;} 
    inline int getWidth(void){return width;} 
    inline void setHeight(const int & h){height = h;} 
    inline void setWidth(const int & w){width = w;} 
private: 
    int height; 
    int width; 
    float endianess; 
}; 

#endif /* PGM_H_ */ 

请原谅我在代码中留下大量无用的注释。

一个简单的例子示出了写入/读出：

int main(){ 
     PFM pfm_rw; 
     string temp = "img/Motorcycle/disp0GT.pfm"; 
     float * p_disp_gt = pfm_rw.read_pfm<float>(temp); 
     //int imgH = pfm_rw.getHeight(); 
     //int imgW = pfm_rw.getWidth(); 
     //float scale = pfm_rw.getEndianess(); 
     string temp2 = "result/Motorcycle/disp0GT_n1.pfm"; 
     pfm_rw.write_pfm<float>(temp2, p_disp_gt, -1.0f); 
     return 1; 
} 

Answer 2

据我所知，OpenCV不支持直接读取PFM文件。

你可以参考的代码片段here一个简单的PFM阅读器，这将使你读PFM文件到COLOR *data与COLOR定义如下：根据” .PFM的描述

typedef struct { 
    float r; 
    float g; 
    float b; 
} COLOR;