readpng.c

zgv-5.6,一个Linux系统下的图片浏览器(VGA/SVGA)

/* Zgv v3.0 - GIF, JPEG and PBM/PGM/PPM viewer, for VGA PCs running Linux.
 * Copyright (C) 1993-1998 Russell Marks. See README for license details.
 *
 * readpng.c - interface to pnglib, derived from their example.c
 *              and readjpeg.c.
 */

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <png.h>
#include <setjmp.h>	/* after png.h to avoid horrible thing in pngconf.h */
#include "zgv.h"
#include "3deffects.h"
#include "readpng.h"
#include "readpnm.h"
#include "vgadisp.h"   /* for pixelsize */
#include "rc_config.h"
#include "rcfile.h"


/* prototypes */
void aborted_file_png_cleanup(void);
int read_png_file(char *filename, hffunc howfarfunc, byte **palette);
void unpack_bits(int bit_depth, unsigned char *rowptr, int width, int height);


hffunc howfar;

/* we need to use all this stuff from vgadisp.c */
extern int width,height,numcols;
extern byte *theimage;
static byte *pal;

/* our png clean up routine (for zgv.c) needs this */
FILE *global_png_infile;

/* must be global to allow aborting in mid-read */
static png_structp png_ptr;
static png_infop info_ptr;
static int number_passes,ilheight,dithering;

static int use_errmsg=0;



/* we call this (from zgv.c) if we aborted.
 * we use the setjmpbuf from zgv.c.
 */
void aborted_file_png_cleanup()
{
png_destroy_read_struct(&png_ptr,&info_ptr,NULL);
free(pal);
fclose(global_png_infile);
}


void my_png_error(png_structp png_ptr,const char *message)
{
strncpy(jpeg_png_errmsg,message,JPEG_PNG_ERRMSG_SIZE-1);
jpeg_png_errmsg[JPEG_PNG_ERRMSG_SIZE-1]=0;
use_errmsg=1;

/* cleanup is done after jump back, so just do that now... */
longjmp(png_ptr->jmpbuf,1);
}


/* No warning messages */
void my_png_warning(png_structp png_ptr,const char *message)
{
}


static void dither_png(hffunc howfarfunc,int number_passes,int ilheight)
{
unsigned char *ptr;
int y;

/* ok, we have 3*width*height allocated (actually 3*width*(height+2),
 * but let's not be pedantic :-)). This currently contains the
 * 24-bit image. If we dither this into the same space, it works
 * ok and doesn't overwrite anything as it goes. We then, for each
 * line, have to copy it into the right place in the new 8-bit image.
 * plus we should call the howfar func. as dithering counts as the
 * 2nd 50% of loading.
 */
for(y=0,ptr=theimage;y<height;y++,ptr+=width*3)
  {
  ditherline(ptr,y,width);
  if(y>0) memcpy(theimage+y*width,ptr,width);
  if(howfarfunc!=NULL) howfarfunc(ilheight+y*number_passes,ilheight*2);
  }

ditherfinish();
pixelsize=1;
}


int read_png_file(char *filename,hffunc howfarfunc,byte **palette)
{
static FILE *in;
unsigned char *rowptr;
png_uint_32 uw,uh;
int f,y;
int bitdepth,colourtype,interlacetype;
png_color_16 my_background={0,0,0,0,0};

use_errmsg=0;
theimage=NULL;

if(((*palette)=(byte *)calloc(768,1))==NULL)
  return(_PICERR_NOMEM);
pal=*palette;

if((in=global_png_infile=fopen(filename,"rb"))==NULL)
  return(_PICERR_NOFILE);

png_ptr=png_create_read_struct(PNG_LIBPNG_VER_STRING,NULL,
	my_png_error,my_png_warning);
if(png_ptr==NULL)
  {
  free(pal); fclose(in);
  return(_PICERR_NOMEM);
  }

if((info_ptr=png_create_info_struct(png_ptr))==NULL)
  {
  free(pal); fclose(in);
  png_destroy_read_struct(&png_ptr,NULL,NULL);
  return(_PICERR_NOMEM);
  }

if(setjmp(png_ptr->jmpbuf))
  {
  /* if we get here, there was an error. */
  /* don't use local variables here, they may have been blasted */
  png_destroy_read_struct(&png_ptr,&info_ptr,NULL);
  fclose(global_png_infile);	/* this uses the global FILE *. */
  if(!cfg.errignore) free(pal);
  if(cfg.errignore && theimage!=NULL && dithering)
    dither_png(NULL,number_passes,ilheight);
  if(use_errmsg)
    return(_PICERR_SEE_ERRMSG);
  else
    return(_PICERR_CORRUPT);	/* could actually be anything... */
  }

png_init_io(png_ptr,in);
png_read_info(png_ptr,info_ptr);

/* the uw/uh stuff is to avoid a `pointer mismatch' compiler warning */
png_get_IHDR(png_ptr,info_ptr,&uw,&uh,&bitdepth,
	&colourtype,&interlacetype,(int *)NULL,(int *)NULL);
width=uw; height=uh;

/* now lots and lots of config stuff... */

if(bitdepth==16)
  png_set_strip_16(png_ptr);

png_set_packing(png_ptr);

png_set_background(png_ptr,&my_background,1.0,0,1.0);

/* doing this here will result in it allocating enough
 * for the 24-bit image even if it will be dithered. This is *required*
 * given the way we have to dither, in case a file is interlaced.
 */
if((colourtype==PNG_COLOR_TYPE_RGB || colourtype==PNG_COLOR_TYPE_RGB_ALPHA) &&
   (pixelsize==1 || cfg.jpeg24bit==0))		/* dither? */
  {
  pixelsize=3;
  if(ditherinit(width)==0)
    return(_PICERR_NOMEM);
  make_332_palette(pal);
  dithering=1;
  }
else
  dithering=0;

if(colourtype==PNG_COLOR_TYPE_GRAY && bitdepth<8)
  png_set_expand(png_ptr);

if(colourtype==PNG_COLOR_TYPE_GRAY ||
   colourtype==PNG_COLOR_TYPE_GRAY_ALPHA ||
   colourtype==PNG_COLOR_TYPE_PALETTE)
  pixelsize=1;

if(colourtype==PNG_COLOR_TYPE_GRAY ||
   colourtype==PNG_COLOR_TYPE_GRAY_ALPHA)
  {
  pixelsize=1;
  for(f=0;f<256;f++)
    pal[f]=pal[256+f]=pal[512+f]=f;
  }

/* XXX should do gamma stuff */

/* output BGR if applicable, not RGB */
png_set_bgr(png_ptr);

number_passes=png_set_interlace_handling(png_ptr);

/* fix palette (probably not needed now, but will be if I do gamma later) */
png_read_update_info(png_ptr,info_ptr);

if(colourtype==PNG_COLOR_TYPE_PALETTE)
  {
  png_colorp cols;
  int palsiz;
  
  png_get_PLTE(png_ptr,info_ptr,&cols,&palsiz);
  for(f=0;f<palsiz;f++)
    {
    pal[    f]=cols[f].red;
    pal[256+f]=cols[f].green;
    pal[512+f]=cols[f].blue;
    }
  }


/* allocate image memory (with two extra lines for dithering) */
theimage=(byte *)malloc(pixelsize*width*(height+2));
if(theimage==NULL) return(_PICERR_NOMEM);


ilheight=height*number_passes;

if(cfg.errignore)
  memset(theimage,0,width*(height+1)*pixelsize);

/* read the image */
for(y=0;y<ilheight;y++)
  {
  rowptr=theimage+(y%height)*width*pixelsize;
  if(cfg.errignore && number_passes>1)	/* fully draw interlace bits */
    png_read_rows(png_ptr,NULL,&rowptr,1);
  else
    png_read_rows(png_ptr,&rowptr,NULL,1);
  
  if(howfarfunc!=NULL) howfarfunc(y,dithering?ilheight*2:ilheight);
  }

/* dither if needed */
if(dithering) dither_png(howfarfunc,number_passes,ilheight);

png_read_end(png_ptr,info_ptr);
png_destroy_read_struct(&png_ptr,&info_ptr,NULL);
fclose(in);

return(_PIC_OK);
}