pngwrite.c

/* pngwrite.c - general routines to write a png file

   libpng 1.0 beta 1 - version 0.71
   For conditions of distribution and use, see copyright notice in png.h
   Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc.
   June 26, 1995
   */

/* get internal access to png.h */
#define PNG_INTERNAL
#include "png.h"

/* Writes all the png information.  This is the suggested way to use
   the library.  If you have a new chunk to add, make a function to
   write it, and put it in the correct location here.  If you want
   the chunk written after the image data, put it in png_write_end().
   I strongly encurage you to supply a PNG_INFO_ flag, and check
   info->valid before writing the chunk, as that will keep the code
   from breaking if you want to just write a plain png file.
   If you have long comments, I suggest writing them in png_write_end(),
   and compressing them. */
void
png_write_info(png_struct *png_ptr, png_info *info)
{
   png_write_sig(png_ptr); /* write PNG signature */
   /* write IHDR information. */
   png_write_IHDR(png_ptr, info->width, info->height, info->bit_depth,
      info->color_type, info->compression_type, info->filter_type,
      info->interlace_type);
   /* the rest of these check to see if the valid field has the appropriate
      flag set, and if it does, writes the chunk. */
   if (info->valid & PNG_INFO_gAMA)
      png_write_gAMA(png_ptr, info->gamma);
   if (info->valid & PNG_INFO_sBIT)
      png_write_sBIT(png_ptr, &(info->sig_bit), info->color_type);
   if (info->valid & PNG_INFO_cHRM)
      png_write_cHRM(png_ptr,
         info->x_white, info->y_white,
         info->x_red, info->y_red,
         info->x_green, info->y_green,
         info->x_blue, info->y_blue);
   if (info->valid & PNG_INFO_PLTE)
      png_write_PLTE(png_ptr, info->palette, info->num_palette);
   if (info->valid & PNG_INFO_tRNS)
      png_write_tRNS(png_ptr, info->trans, &(info->trans_values),
         info->num_trans, info->color_type);
   if (info->valid & PNG_INFO_bKGD)
      png_write_bKGD(png_ptr, &(info->background), info->color_type);
   if (info->valid & PNG_INFO_hIST)
      png_write_hIST(png_ptr, info->hist, info->num_palette);
   if (info->valid & PNG_INFO_pHYs)
      png_write_pHYs(png_ptr, info->x_pixels_per_unit,
         info->y_pixels_per_unit, info->phys_unit_type);
   if (info->valid & PNG_INFO_oFFs)
      png_write_oFFs(png_ptr, info->x_offset, info->y_offset,
         info->offset_unit_type);
   if (info->valid & PNG_INFO_tIME)
      png_write_tIME(png_ptr, &(info->mod_time));
   /* Check to see if we need to write text chunks */
   if (info->num_text)
   {
      int i; /* local counter */

      /* loop through the text chunks */
      for (i = 0; i < info->num_text; i++)
      {
         /* if chunk is compressed */
         if (info->text[i].compression >= 0)
         {
            /* write compressed chunk */
            png_write_zTXt(png_ptr, info->text[i].key,
               info->text[i].text, info->text[i].text_length,
               info->text[i].compression);
         }
         else
         {
            /* write uncompressed chunk */
            png_write_tEXt(png_ptr, info->text[i].key,
               info->text[i].text, info->text[i].text_length);
         }
      }
   }
}

/* writes the end of the png file.  If you don't want to write comments or
   time information, you can pass NULL for info.  If you already wrote these
   in png_write_info(), do not write them again here.  If you have long
   comments, I suggest writing them here, and compressing them. */
void
png_write_end(png_struct *png_ptr, png_info *info)
{
   /* see if user wants us to write information chunks */
   if (info)
   {
      /* check to see if user has supplied a time chunk */
      if (info->valid & PNG_INFO_tIME)
         png_write_tIME(png_ptr, &(info->mod_time));
      /* check to see if we need to write comment chunks */
      if (info->num_text)
      {
         int i; /* local index variable */

         /* loop through comment chunks */
         for (i = 0; i < info->num_text; i++)
         {
            /* check to see if comment is to be compressed */
            if (info->text[i].compression >= 0)
            {
               /* write compressed chunk */
               png_write_zTXt(png_ptr, info->text[i].key,
                  info->text[i].text, info->text[i].text_length,
                  info->text[i].compression);
            }
            else
            {
               /* write uncompressed chunk */
               png_write_tEXt(png_ptr, info->text[i].key,
                  info->text[i].text, info->text[i].text_length);
            }
         }
      }
   }
   /* write end of png file */
   png_write_IEND(png_ptr);
}

/* initialize the info structure */
void
png_info_init(png_info *info)
{
   /* set everything to 0 */
   memset(info, 0, sizeof (png_info));
}

void
png_convert_from_struct_tm(png_time *ptime, struct tm *ttime)
{
   ptime->year = 1900 + ttime->tm_year;
   ptime->month = ttime->tm_mon + 1;
   ptime->day = ttime->tm_mday;
   ptime->hour = ttime->tm_hour;
   ptime->minute = ttime->tm_min;
   ptime->second = ttime->tm_sec;
}

void
png_convert_from_time_t(png_time *ptime, time_t ttime)
{
   struct tm *tbuf;

   tbuf = gmtime(&ttime);
   png_convert_from_struct_tm(ptime, tbuf);
}

/* initialize png structure, and allocate any memory needed */
void
png_write_init(png_struct *png_ptr)
{
   jmp_buf tmp_jmp; /* to save current jump buffer */

   /* save jump buffer */
   memcpy(tmp_jmp, png_ptr->jmpbuf, sizeof (jmp_buf));
   /* reset all variables to 0 */
   memset(png_ptr, 0, sizeof (png_struct));
   /* restore jump buffer */
   memcpy(png_ptr->jmpbuf, tmp_jmp, sizeof (jmp_buf));

   /* initialize zbuf - compression buffer */
   png_ptr->zbuf_size = PNG_ZBUF_SIZE;
   png_ptr->zbuf = png_large_malloc(png_ptr, png_ptr->zbuf_size);
   /* initialize zlib */
   png_ptr->zstream = &(png_ptr->zstream_struct);
   png_ptr->zstream->zalloc = png_zalloc;
   png_ptr->zstream->zfree = png_zfree;
   png_ptr->zstream->opaque = (voidp)png_ptr;
   deflateInit(png_ptr->zstream, Z_BEST_COMPRESSION);
   png_ptr->zstream->next_out = png_ptr->zbuf;
   png_ptr->zstream->avail_out = (uInt)png_ptr->zbuf_size;
}

/* write a few rows of image data.  If the image is interlaced,
   either you will have to write the 7 sub images, or, if you
   have called png_set_interlace_handling(), you will have to
   "write" the image seven times */
void
png_write_rows(png_struct *png_ptr, png_byte **row,
   png_uint_32 num_rows)
{
   png_uint_32 i; /* row counter */
   png_byte **rp; /* row pointer */

   /* loop through the rows */
   for (i = 0, rp = row; i < num_rows; i++, rp++)
   {
      png_write_row(png_ptr, *rp);
   }
}

/* write the image.  You only need to call this function once, even
   if you are writing an interlaced image. */
void
png_write_image(png_struct *png_ptr, png_byte **image)
{
   png_uint_32 i; /* row index */
   int pass, num_pass; /* pass variables */
   png_byte **rp; /* points to current row */

   /* intialize interlace handling.  If image is not interlaced,
      this will set pass to 1 */
   num_pass = png_set_interlace_handling(png_ptr);
   /* loop through passes */
   for (pass = 0; pass < num_pass; pass++)
   {
      /* loop through image */
      for (i = 0, rp = image; i < png_ptr->height; i++, rp++)
      {
         png_write_row(png_ptr, *rp);
      }
   }
}

/* write a row of image data */
void
png_write_row(png_struct *png_ptr, png_byte *row)
{
   /* initialize transformations and other stuff if first time */
   if (png_ptr->row_number == 0 && png_ptr->pass == 0)
   {
      png_write_start_row(png_ptr);
   }

   /* if interlaced and not interested in row, return */
   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
   {
      switch (png_ptr->pass)
      {
         case 0:
            if (png_ptr->row_number & 7)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;
         case 1:
            if ((png_ptr->row_number & 7) || png_ptr->width < 5)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;
         case 2:
            if ((png_ptr->row_number & 7) != 4)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;
         case 3:
            if ((png_ptr->row_number & 3) || png_ptr->width < 3)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;
         case 4:
            if ((png_ptr->row_number & 3) != 2)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;
         case 5:
            if ((png_ptr->row_number & 1) || png_ptr->width < 2)
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;
         case 6:
            if (!(png_ptr->row_number & 1))
            {
               png_write_finish_row(png_ptr);
               return;
            }
            break;
      }
   }

   /* set up row info for transformations */
   png_ptr->row_info.color_type = png_ptr->color_type;
   png_ptr->row_info.width = png_ptr->usr_width;
   png_ptr->row_info.channels = png_ptr->usr_channels;
   png_ptr->row_info.bit_depth = png_ptr->usr_bit_depth;
   png_ptr->row_info.pixel_depth = png_ptr->row_info.bit_depth *
      png_ptr->row_info.channels;
   png_ptr->row_info.rowbytes = ((png_ptr->row_info.width *
      (png_uint_32)png_ptr->row_info.pixel_depth + 7) >> 3);

   /* copy users row into buffer, leaving room for filter byte */
   memcpy(png_ptr->row_buf + 1, row, (png_size_t)png_ptr->row_info.rowbytes);

   /* handle interlacing */
   if (png_ptr->interlaced && png_ptr->pass < 6 &&
      (png_ptr->transformations & PNG_INTERLACE))
   {
      png_do_write_interlace(&(png_ptr->row_info),
         png_ptr->row_buf + 1, png_ptr->pass);
      /* this should always get caught above, but still ... */
      if (!(png_ptr->row_info.width))
      {
         png_write_finish_row(png_ptr);
         return;
      }
   }

   /* handle other transformations */
   if (png_ptr->transformations)
      png_do_write_transformations(png_ptr);

   /* filter rows that have been proved to help */
   if (png_ptr->bit_depth >= 8 && png_ptr->color_type != 3)
   {
      /* save row to previous row */
      memcpy(png_ptr->save_row, png_ptr->row_buf,
         (png_size_t)png_ptr->row_info.rowbytes + 1);

      /* filter row */
      png_write_filter_row(&(png_ptr->row_info), png_ptr->row_buf,
         png_ptr->prev_row);

      /* trade saved pointer and prev pointer so next row references are correctly */
      { /* scope limiter */
         png_byte *tptr;

         tptr = png_ptr->prev_row;
         png_ptr->prev_row = png_ptr->save_row;
         png_ptr->save_row = tptr;
      }
   }
   else
      /* set filter row to "none" */
      png_ptr->row_buf[0] = 0;

   /* set up the zlib input buffer */
   png_ptr->zstream->next_in = png_ptr->row_buf;
   png_ptr->zstream->avail_in = (uInt)png_ptr->row_info.rowbytes + 1;

#ifdef zlibinout
/* temp zlib problem */
{
   extern FILE *fpzlibin;

   fwrite(png_ptr->row_buf, 1, png_ptr->zstream->avail_in, fpzlibin);
}
/* end temp zlib problem */
#endif

   /* repeat until we have compressed all the data */
   do
   {
      int ret; /* return of zlib */

      /* compress the data */
      ret = deflate(png_ptr->zstream, Z_NO_FLUSH);
      /* check for compression errors */
      if (ret != Z_OK)
      {
         if (png_ptr->zstream->msg)
            png_error(png_ptr, png_ptr->zstream->msg);
         else
            png_error(png_ptr, "zlib error");
      }

      /* see if it is time to write another IDAT */
      if (!png_ptr->zstream->avail_out)
      {
         /* write the IDAT and reset the zlib output buffer */
         png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
         png_ptr->zstream->next_out = png_ptr->zbuf;
         png_ptr->zstream->avail_out = (uInt)png_ptr->zbuf_size;
      }
   /* repeat until all data has been compressed */
   } while (png_ptr->zstream->avail_in);

   /* finish row - updates counters and flushes zlib if last row */
   png_write_finish_row(png_ptr);
}

/* free any memory used in png struct */
void
png_write_destroy(png_struct *png_ptr)
{
   jmp_buf tmp_jmp; /* save jump buffer */

   /* free any memory zlib uses */
   deflateEnd(png_ptr->zstream);
   /* free our memory.  png_free checks NULL for us. */
   png_large_free(png_ptr, png_ptr->zbuf);
   png_large_free(png_ptr, png_ptr->row_buf);
   png_large_free(png_ptr, png_ptr->prev_row);
   png_large_free(png_ptr, png_ptr->save_row);
   /* reset structure */
   memcpy(tmp_jmp, png_ptr->jmpbuf, sizeof (jmp_buf));
   memset(png_ptr, 0, sizeof (png_struct));
   memcpy(png_ptr->jmpbuf, tmp_jmp, sizeof (jmp_buf));
}