dec_png.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <png.h>
 
#ifdef __64BIT__
  typedef int g2int; 
#else
  typedef long g2int; 
#endif
 
#if defined CRAY90
   #include <fortran.h>
   #define SUB_NAME DEC_PNG
#elif defined LINUXF90
   #define SUB_NAME DEC_PNG
#elif defined LINUXG95
   #define SUB_NAME dec_png__
#elif defined HP || defined AIX
   #define SUB_NAME dec_png
#elif defined SGI || defined LINUX || defined VPP5000 || defined APPLE
   #define SUB_NAME dec_png_
#endif
 
struct png_stream {
   unsigned char *stream_ptr;     
   g2int stream_len;              
};
typedef struct png_stream png_stream; 
void user_read_data(png_structp , png_bytep , png_uint_32 );
 
void user_read_data(png_structp png_ptr,png_bytep data, png_uint_32 length)
 
 
{
     char *ptr;
     g2int offset;
     png_stream *mem;
 
     mem=(png_stream *)png_get_io_ptr(png_ptr);
     ptr=(void *)mem->stream_ptr;
     offset=mem->stream_len;
/*     printf("SAGrd %ld %ld %x\n",offset,length,ptr);  */
     memcpy(data,ptr+offset,length);
     mem->stream_len += length;
}
 
int SUB_NAME(unsigned char *pngbuf,g2int *width,g2int *height,char *cout)
{
    int interlace,color,compres,filter,bit_depth;
    g2int j,k,n,bytes,clen;
    png_structp png_ptr;
    png_infop info_ptr,end_info;
    png_bytepp row_pointers;
    png_stream read_io_ptr;
    png_uint_32 h32, w32;
 
/*
**  check if stream is a valid PNG format  
*/
 
    if ( png_sig_cmp(pngbuf,0,8) != 0) 
       return (-3);
 
/*
** create and initialize png_structs 
*/
 
    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, (png_voidp)NULL, 
                                      NULL, NULL);
    if (!png_ptr)
       return (-1);
 
    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr)
    {
       png_destroy_read_struct(&png_ptr,(png_infopp)NULL,(png_infopp)NULL);
       return (-2);
    }
 
    end_info = png_create_info_struct(png_ptr);
    if (!end_info)
    {
       png_destroy_read_struct(&png_ptr,(png_infopp)info_ptr,(png_infopp)NULL);
       return (-2);
    }
 
/* 
**     Set Error callback  
*/
 
    if (setjmp(png_jmpbuf(png_ptr)))
    {
       png_destroy_read_struct(&png_ptr, &info_ptr,&end_info);
       return (-3);
    }
 
/*
**    Initialize info for reading PNG stream from memory 
*/
 
    read_io_ptr.stream_ptr=(png_voidp)pngbuf;
    read_io_ptr.stream_len=0;
 
/*
**    Set new custom read function 
*/
 
    png_set_read_fn(png_ptr,(png_voidp)&read_io_ptr,(png_rw_ptr)user_read_data);
 
/*     png_init_io(png_ptr, fptr); */
 
/*
**     Read and decode PNG stream 
*/
 
    png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
 
/*
**     Get pointer to each row of image data 
*/
 
    row_pointers = png_get_rows(png_ptr, info_ptr);
 
/*
**      Get image info, such as size, depth, colortype, etc...  
*/
 
/*    printf("SAGT:png %d %d %d\n",info_ptr->width,info_ptr->height,info_ptr->bit_depth);*/
/*    (void)png_get_IHDR(png_ptr, info_ptr, (png_uint_32 *)width, (png_uint_32 *)height,
               &bit_depth, &color, &interlace, &compres, &filter);*/
    (void)png_get_IHDR(png_ptr, info_ptr, &w32, &h32,
               &bit_depth, &color, &interlace, &compres, &filter);
 
    *height = h32;
    *width = w32;
 
/*
**     Check if image was grayscale  
*/
 
/*
    if (color != PNG_COLOR_TYPE_GRAY ) {
       fprintf(stderr,"dec_png: Grayscale image was expected. \n");
    }
*/
    if ( color == PNG_COLOR_TYPE_RGB ) {
       bit_depth=24;
    }
    else if ( color == PNG_COLOR_TYPE_RGB_ALPHA ) {
       bit_depth=32;
    }
/*
**     Copy image data to output string 
*/
 
    n=0;
    bytes=bit_depth/8;
    clen=(*width)*bytes;
    for (j=0;j<*height;j++) {
      for (k=0;k<clen;k++) {
        cout[n]=*(row_pointers[j]+k);
        n++;
      }
    }
 
/*
**     Clean up
*/
 
    png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
    return 0;
 
}