#ifndef _PNG_H
#define _PNG_H

#include <zlib.h>

#ifndef BSIZE
#define BSIZE 20480
#endif

#define byte unsigned char

struct png_internal_struct
{
   unsigned long width;
   unsigned long height;
   byte bit_depth, color_type, comression, filter, interlace;
   byte PLTE;
   FILE *png;
   byte position;
   /* position in file:
      0: between chunks (between crc of old and length of new)
      1: before chunk data (length + header already read)
      2: after chunk data (crc not yet read)
   */
   unsigned long length, crc;
   char chunk_type[4];
   /* values of chunk read last */
   unsigned char *mem_ptr;
   z_stream d_stream;
   /* for zlib library status */
   int zlib_initialized;
   int readbuf_initialized;
   byte *readbuf;
   int buf_pos, buf_filled;
   unsigned long chunk_pos;
   unsigned long checksum;
} ;

struct png_info_struct
{
   unsigned long width;
   unsigned long height;
   byte bit_depth, color_type, compression, filter, interlace;
};

#ifdef __cplusplus
extern "C" {
#endif
int CorrectLong1(unsigned long *l, unsigned char *Buf);
int CorrectLong2(unsigned char *Buf, unsigned long *l);
int InitPNG(FILE *png, struct png_info_struct *info, struct png_internal_struct *internal);
   /* Has to be called after opening and before reading the PNG file      */
   /* returns -1 if png signature check failed or first chunk is not IHDR */
int GetNextChunk(struct png_internal_struct *i);
   /* Reads length and chunk type of next chunk in file */
   /* and sets fields length and chunk_type */
int ReadChunkData(struct png_internal_struct *i, byte *mem);
   /* Reads data of a chunk. It is required that the length and header */
   /* of the chunk has already been read. If not, function returns */
   /* -1. -2 indicates an invalid CRC */
int do_inflate(struct png_internal_struct *i);
   /* is used to call the function for decompressing of zlib */
   /* returns return code of zlib and 10 if Z_STREAM_END */
int ReadPNGLine(struct png_internal_struct *i, unsigned char *Buf);
   /* reads and decompresses a single line (+ filter byte) from file into Buf */
   /* -1 if file position isn't at the beginning of an IDAT chunk */
   /* -2 CRC error */
   /* -3 if the next chunk needed to reconstruct line isn't IDAT */
int DoUnFiltering(struct png_internal_struct *i, unsigned char *Buf, unsigned char *Buf_up);
   /* This funtion is feeded with a line aquired by ReadPNGLine (*buf) */
   /* It calculates filtered data -> raw data */
   /* Buf up is the raw date of the line above. May be NULL */
int DoFiltering(struct png_internal_struct *i, unsigned char *Buf);
int InitWritePNG(FILE *png, struct png_info_struct *info, struct png_internal_struct *i);
int WriteChunk(struct png_internal_struct *i, unsigned char *Buf);
int WritePNGLine(struct png_internal_struct *i, unsigned char *Buf);
int EndIDAT(struct png_internal_struct *i);
int PosOverIEND(struct png_internal_struct *i);
int PosOverIHDR(struct png_internal_struct *i);
int EndPNG(struct png_internal_struct *i);

#ifdef __cplusplus
}
#endif
#endif