#ifndef _H_RGBE
#define _H_RGBE
/* THIS CODE CARRIES NO GUARANTEE OF USABILITY OR FITNESS FOR ANY PURPOSE.
 *  * WHILE THE AUTHORS HAVE TRIED TO ENSURE THE PROGRAM WORKS CORRECTLY,
 *   * IT IS STRICTLY USE AT YOUR OWN RISK.  */

/* utility for reading and writing Ward's rgbe image format.
 *    See rgbe.txt file for more details.
 *    */

#include <stdio.h>
#include <math.h>

typedef struct {
  int valid;            /* indicate which fields are valid */
  char programtype[16]; /* listed at beginning of file to identify it 
                         * after "#?".  defaults to "RGBE" */ 
  float gamma;          /* image has already been gamma corrected with 
                         * given gamma.  defaults to 1.0 (no correction) */
  float exposure;       /* a value of 1.0 in an image corresponds to
			 * <exposure> watts/steradian/m^2. 
			 * 			 * defaults to 1.0 */
} rgbe_header_info;

/* flags indicating which fields in an rgbe_header_info are valid */
#define RGBE_VALID_PROGRAMTYPE 0x01
#define RGBE_VALID_GAMMA       0x02
#define RGBE_VALID_EXPOSURE    0x04

/* return codes for rgbe routines */
#define RGBE_RETURN_SUCCESS 0
#define RGBE_RETURN_FAILURE -1

/* read or write headers */
/* you may set rgbe_header_info to null if you want to */
int RGBE_WriteHeader(FILE *fp, int width, int height, rgbe_header_info *info);
int RGBE_ReadHeader(FILE *fp, int *width, int *height, rgbe_header_info *info);

/* read or write pixels */
/* can read or write pixels in chunks of any size including single pixels*/
int RGBE_WritePixels(FILE *fp, float *data, int numpixels);
int RGBE_ReadPixels(FILE *fp, float *data, int numpixels);

/* read or write run length encoded files */
/* must be called to read or write whole scanlines */
int RGBE_WritePixels_RLE(FILE *fp, float *data, int scanline_width,
			 int num_scanlines);
int RGBE_ReadPixels_RLE(FILE *fp, float *data, int scanline_width,
			int num_scanlines);

/* standard conversion from float pixels to rgbe pixels */
/* note: you can remove the "inline"s if your compiler complains about it */
static 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 = 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);
  }
}

#endif /* _H_RGBE */