opencv/modules/imgcodecs/src/rgbe.cpp

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#include "precomp.hpp"
#include "rgbe.hpp"
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

// This file contains code to read and write four byte rgbe file format
// developed by Greg Ward.  It handles the conversions between rgbe and
// pixels consisting of floats.  The data is assumed to be an array of floats.
// By default there are three floats per pixel in the order red, green, blue.
// (RGBE_DATA_??? values control this.)  Only the mimimal header reading and
// writing is implemented.  Each routine does error checking and will return
// a status value as defined below.  This code is intended as a skeleton so
// feel free to modify it to suit your needs.

// Some opencv specific changes have been added:
// inline define specified, error handler uses CV_Error,
// defines changed to work in bgr color space.
//
// posted to http://www.graphics.cornell.edu/~bjw/
// written by Bruce Walter  (bjw@graphics.cornell.edu)  5/26/95
// based on code written by Greg Ward

#define INLINE inline

/* offsets to red, green, and blue components in a data (float) pixel */
#define RGBE_DATA_RED    2
#define RGBE_DATA_GREEN  1
#define RGBE_DATA_BLUE   0
/* number of floats per pixel */
#define RGBE_DATA_SIZE   3

enum rgbe_error_codes {
  rgbe_read_error,
  rgbe_write_error,
  rgbe_format_error,
  rgbe_memory_error
};

/* default error routine.  change this to change error handling */
static int rgbe_error(int rgbe_error_code, const char *msg)
{
  switch (rgbe_error_code) {
  case rgbe_read_error:
       CV_Error(cv::Error::StsError, "RGBE read error");
       break;
  case rgbe_write_error:
       CV_Error(cv::Error::StsError, "RGBE write error");
       break;
  case rgbe_format_error:
       CV_Error(cv::Error::StsError, cv::String("RGBE bad file format: ") +
                       cv::String(msg));
       break;
  default:
  case rgbe_memory_error:
       CV_Error(cv::Error::StsError, cv::String("RGBE error: \n") +
                     cv::String(msg));
  }
}

/* standard conversion from float pixels to rgbe pixels */
/* note: you can remove the "inline"s if your compiler complains about it */
static INLINE void
float2rgbe(unsigned char rgbe[4], float red, float green, float blue)
{
  float v;
  int e;

  v = red;
  if (green > v) v = green;
  if (blue > v) v = blue;
  if (v < 1e-32) {
    rgbe[0] = rgbe[1] = rgbe[2] = rgbe[3] = 0;
  }
  else {
    v = static_cast<float>(frexp(v,&e) * 256.0/v);
    rgbe[0] = (unsigned char) (red * v);
    rgbe[1] = (unsigned char) (green * v);
    rgbe[2] = (unsigned char) (blue * v);
    rgbe[3] = (unsigned char) (e + 128);
  }
}

/* standard conversion from rgbe to float pixels */
/* note: Ward uses ldexp(col+0.5,exp-(128+8)).  However we wanted pixels */
/*       in the range [0,1] to map back into the range [0,1].            */
static INLINE void
rgbe2float(float *red, float *green, float *blue, unsigned char rgbe[4])
{
  float f;

  if (rgbe[3]) {   /*nonzero pixel*/
    f = static_cast<float>(ldexp(1.0,rgbe[3]-(int)(128+8)));
    *red = rgbe[0] * f;
    *green = rgbe[1] * f;
    *blue = rgbe[2] * f;
  }
  else
    *red = *green = *blue = 0.0;
}

/* default minimal header. modify if you want more information in header */
int RGBE_WriteHeader(FILE *fp, int width, int height, rgbe_header_info *info)
{
  const char *programtype = "RGBE";

  if (info && (info->valid & RGBE_VALID_PROGRAMTYPE))
    programtype = info->programtype;
  if (fprintf(fp,"#?%s\n",programtype) < 0)
    return rgbe_error(rgbe_write_error,NULL);
  /* The #? is to identify file type, the programtype is optional. */
  if (info && (info->valid & RGBE_VALID_GAMMA)) {
    if (fprintf(fp,"GAMMA=%g\n",info->gamma) < 0)
      return rgbe_error(rgbe_write_error,NULL);
  }
  if (info && (info->valid & RGBE_VALID_EXPOSURE)) {
    if (fprintf(fp,"EXPOSURE=%g\n",info->exposure) < 0)
      return rgbe_error(rgbe_write_error,NULL);
  }
  if (fprintf(fp,"FORMAT=32-bit_rle_rgbe\n\n") < 0)
    return rgbe_error(rgbe_write_error,NULL);
  if (fprintf(fp, "-Y %d +X %d\n", height, width) < 0)
    return rgbe_error(rgbe_write_error,NULL);
  return RGBE_RETURN_SUCCESS;
}

/* minimal header reading.  modify if you want to parse more information */
int RGBE_ReadHeader(FILE *fp, int *width, int *height, rgbe_header_info *info)
{
  char buf[128];
  float tempf;
  int i;

  if (info) {
    info->valid = 0;
    info->programtype[0] = 0;
    info->gamma = info->exposure = 1.0;
  }

  // 1. read first line
  if (fgets(buf,sizeof(buf)/sizeof(buf[0]),fp) == NULL)
    return rgbe_error(rgbe_read_error,NULL);
  if ((buf[0] != '#')||(buf[1] != '?')) {
    /* if you want to require the magic token then uncomment the next line */
    /*return rgbe_error(rgbe_format_error,"bad initial token"); */
  }
  else if (info) {
    info->valid |= RGBE_VALID_PROGRAMTYPE;
    for(i=0;i<static_cast<int>(sizeof(info->programtype)-1);i++) {
      if ((buf[i+2] == 0) || isspace(buf[i+2]))
  break;
      info->programtype[i] = buf[i+2];
    }
    info->programtype[i] = 0;
  }

  // 2. reading other header lines
  bool hasFormat = false;
  for(;;) {
    if (fgets(buf,sizeof(buf)/sizeof(buf[0]),fp) == 0)
      return rgbe_error(rgbe_read_error,NULL);
    if (buf[0] == '\n') // end of the header
      break;
    else if (buf[0] == '#') // comment
      continue;
    else if (strcmp(buf,"FORMAT=32-bit_rle_rgbe\n") == 0)
      hasFormat = true;
    else if (info && (sscanf(buf,"GAMMA=%g",&tempf) == 1)) {
      info->gamma = tempf;
      info->valid |= RGBE_VALID_GAMMA;
    }
    else if (info && (sscanf(buf,"EXPOSURE=%g",&tempf) == 1)) {
      info->exposure = tempf;
      info->valid |= RGBE_VALID_EXPOSURE;
    }
  }
  if (strcmp(buf,"\n") != 0)
    return rgbe_error(rgbe_format_error,
          "missing blank line after FORMAT specifier");
  if (!hasFormat)
      return rgbe_error(rgbe_format_error, "missing FORMAT specifier");

  // 3. reading resolution string
  if (fgets(buf,sizeof(buf)/sizeof(buf[0]),fp) == 0)
    return rgbe_error(rgbe_read_error,NULL);
  if (sscanf(buf,"-Y %d +X %d",height,width) < 2)
    return rgbe_error(rgbe_format_error,"missing image size specifier");
  return RGBE_RETURN_SUCCESS;
}

/* simple write routine that does not use run length encoding */
/* These routines can be made faster by allocating a larger buffer and
   fread-ing and fwrite-ing the data in larger chunks */
int RGBE_WritePixels(FILE *fp, float *data, int numpixels)
{
  unsigned char rgbe[4];

  while (numpixels-- > 0) {
    float2rgbe(rgbe,data[RGBE_DATA_RED],
         data[RGBE_DATA_GREEN],data[RGBE_DATA_BLUE]);
    data += RGBE_DATA_SIZE;
    if (fwrite(rgbe, sizeof(rgbe), 1, fp) < 1)
      return rgbe_error(rgbe_write_error,NULL);
  }
  return RGBE_RETURN_SUCCESS;
}

/* simple read routine.  will not correctly handle run length encoding */
int RGBE_ReadPixels(FILE *fp, float *data, int numpixels)
{
  unsigned char rgbe[4];

  while(numpixels-- > 0) {
    if (fread(rgbe, sizeof(rgbe), 1, fp) < 1)
      return rgbe_error(rgbe_read_error,NULL);
    rgbe2float(&data[RGBE_DATA_RED],&data[RGBE_DATA_GREEN],
         &data[RGBE_DATA_BLUE],rgbe);
    data += RGBE_DATA_SIZE;
  }
  return RGBE_RETURN_SUCCESS;
}

/* The code below is only needed for the run-length encoded files. */
/* Run length encoding adds considerable complexity but does */
/* save some space.  For each scanline, each channel (r,g,b,e) is */
/* encoded separately for better compression. */

static int RGBE_WriteBytes_RLE(FILE *fp, unsigned char *data, int numbytes)
{
#define MINRUNLENGTH 4
  int cur, beg_run, run_count, old_run_count, nonrun_count;
  unsigned char buf[2];

  cur = 0;
  while(cur < numbytes) {
    beg_run = cur;
    /* find next run of length at least 4 if one exists */
    run_count = old_run_count = 0;
    while((run_count < MINRUNLENGTH) && (beg_run < numbytes)) {
      beg_run += run_count;
      old_run_count = run_count;
      run_count = 1;
      while( (beg_run + run_count < numbytes) && (run_count < 127)
             && (data[beg_run] == data[beg_run + run_count]))
  run_count++;
    }
    /* if data before next big run is a short run then write it as such */
    if ((old_run_count > 1)&&(old_run_count == beg_run - cur)) {
      buf[0] = static_cast<unsigned char>(128 + old_run_count);   /*write short run*/
      buf[1] = data[cur];
      if (fwrite(buf,sizeof(buf[0])*2,1,fp) < 1)
  return rgbe_error(rgbe_write_error,NULL);
      cur = beg_run;
    }
    /* write out bytes until we reach the start of the next run */
    while(cur < beg_run) {
      nonrun_count = beg_run - cur;
      if (nonrun_count > 128)
  nonrun_count = 128;
      buf[0] = static_cast<unsigned char>(nonrun_count);
      if (fwrite(buf,sizeof(buf[0]),1,fp) < 1)
  return rgbe_error(rgbe_write_error,NULL);
      if (fwrite(&data[cur],sizeof(data[0])*nonrun_count,1,fp) < 1)
  return rgbe_error(rgbe_write_error,NULL);
      cur += nonrun_count;
    }
    /* write out next run if one was found */
    if (run_count >= MINRUNLENGTH) {
      buf[0] = static_cast<unsigned char>(128 + run_count);
      buf[1] = data[beg_run];
      if (fwrite(buf,sizeof(buf[0])*2,1,fp) < 1)
  return rgbe_error(rgbe_write_error,NULL);
      cur += run_count;
    }
  }
  return RGBE_RETURN_SUCCESS;
#undef MINRUNLENGTH
}

int RGBE_WritePixels_RLE(FILE *fp, float *data, int scanline_width,
       int num_scanlines)
{
  unsigned char rgbe[4];
  unsigned char *buffer;
  int i, err;

  if ((scanline_width < 8)||(scanline_width > 0x7fff))
    /* run length encoding is not allowed so write flat*/
    return RGBE_WritePixels(fp,data,scanline_width*num_scanlines);
  buffer = (unsigned char *)malloc(sizeof(unsigned char)*4*scanline_width);
  if (buffer == NULL)
    /* no buffer space so write flat */
    return RGBE_WritePixels(fp,data,scanline_width*num_scanlines);
  while(num_scanlines-- > 0) {
    rgbe[0] = 2;
    rgbe[1] = 2;
    rgbe[2] = static_cast<unsigned char>(scanline_width >> 8);
    rgbe[3] = scanline_width & 0xFF;
    if (fwrite(rgbe, sizeof(rgbe), 1, fp) < 1) {
      free(buffer);
      return rgbe_error(rgbe_write_error,NULL);
    }
    for(i=0;i<scanline_width;i++) {
      float2rgbe(rgbe,data[RGBE_DATA_RED],
     data[RGBE_DATA_GREEN],data[RGBE_DATA_BLUE]);
      buffer[i] = rgbe[0];
      buffer[i+scanline_width] = rgbe[1];
      buffer[i+2*scanline_width] = rgbe[2];
      buffer[i+3*scanline_width] = rgbe[3];
      data += RGBE_DATA_SIZE;
    }
    /* write out each of the four channels separately run length encoded */
    /* first red, then green, then blue, then exponent */
    for(i=0;i<4;i++) {
      if ((err = RGBE_WriteBytes_RLE(fp,&buffer[i*scanline_width],
             scanline_width)) != RGBE_RETURN_SUCCESS) {
  free(buffer);
  return err;
      }
    }
  }
  free(buffer);
  return RGBE_RETURN_SUCCESS;
}

int RGBE_ReadPixels_RLE(FILE *fp, float *data, int scanline_width,
      int num_scanlines)
{
  unsigned char rgbe[4], *scanline_buffer, *ptr, *ptr_end;
  int i, count;
  unsigned char buf[2];

  if ((scanline_width < 8)||(scanline_width > 0x7fff))
    /* run length encoding is not allowed so read flat*/
    return RGBE_ReadPixels(fp,data,scanline_width*num_scanlines);
  scanline_buffer = NULL;
  /* read in each successive scanline */
  while(num_scanlines > 0) {
    if (fread(rgbe,sizeof(rgbe),1,fp) < 1) {
      free(scanline_buffer);
      return rgbe_error(rgbe_read_error,NULL);
    }
    if ((rgbe[0] != 2)||(rgbe[1] != 2)||(rgbe[2] & 0x80)) {
      /* this file is not run length encoded */
      rgbe2float(&data[RGBE_DATA_RED],&data[RGBE_DATA_GREEN],&data[RGBE_DATA_BLUE],rgbe);
      data += RGBE_DATA_SIZE;
      free(scanline_buffer);
      return RGBE_ReadPixels(fp,data,scanline_width*num_scanlines-1);
    }
    if ((((int)rgbe[2])<<8 | rgbe[3]) != scanline_width) {
      free(scanline_buffer);
      return rgbe_error(rgbe_format_error,"wrong scanline width");
    }
    if (scanline_buffer == NULL)
      scanline_buffer = (unsigned char *)
  malloc(sizeof(unsigned char)*4*scanline_width);
    if (scanline_buffer == NULL)
      return rgbe_error(rgbe_memory_error,"unable to allocate buffer space");

    ptr = &scanline_buffer[0];
    /* read each of the four channels for the scanline into the buffer */
    for(i=0;i<4;i++) {
      ptr_end = &scanline_buffer[(i+1)*scanline_width];
      while(ptr < ptr_end) {
  if (fread(buf,sizeof(buf[0])*2,1,fp) < 1) {
    free(scanline_buffer);
    return rgbe_error(rgbe_read_error,NULL);
  }
  if (buf[0] > 128) {
    /* a run of the same value */
    count = buf[0]-128;
    if ((count == 0)||(count > ptr_end - ptr)) {
      free(scanline_buffer);
      return rgbe_error(rgbe_format_error,"bad scanline data");
    }
    while(count-- > 0)
      *ptr++ = buf[1];
  }
  else {
    /* a non-run */
    count = buf[0];
    if ((count == 0)||(count > ptr_end - ptr)) {
      free(scanline_buffer);
      return rgbe_error(rgbe_format_error,"bad scanline data");
    }
    *ptr++ = buf[1];
    if (--count > 0) {
      if (fread(ptr,sizeof(*ptr)*count,1,fp) < 1) {
        free(scanline_buffer);
        return rgbe_error(rgbe_read_error,NULL);
      }
      ptr += count;
    }
  }
      }
    }
    /* now convert data from buffer into floats */
    for(i=0;i<scanline_width;i++) {
      rgbe[0] = scanline_buffer[i];
      rgbe[1] = scanline_buffer[i+scanline_width];
      rgbe[2] = scanline_buffer[i+2*scanline_width];
      rgbe[3] = scanline_buffer[i+3*scanline_width];
      rgbe2float(&data[RGBE_DATA_RED],&data[RGBE_DATA_GREEN],
     &data[RGBE_DATA_BLUE],rgbe);
      data += RGBE_DATA_SIZE;
    }
    num_scanlines--;
  }
  free(scanline_buffer);
  return RGBE_RETURN_SUCCESS;
}