chromium/third_party/libpng/pngwrite.c

/* pngwrite.c - general routines to write a PNG file
 *
 * Copyright (c) 2018-2024 Cosmin Truta
 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
 * Copyright (c) 1996-1997 Andreas Dilger
 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 */

#include "pngpriv.h"
#ifdef PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED
#  include <errno.h>
#endif /* SIMPLIFIED_WRITE_STDIO */

#ifdef PNG_WRITE_SUPPORTED

#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
/* Write out all the unknown chunks for the current given location */
static void
write_unknown_chunks(png_structrp png_ptr, png_const_inforp info_ptr,
    unsigned int where)
{ … }
#endif /* WRITE_UNKNOWN_CHUNKS */

/* 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 encourage
 * you to supply a PNG_INFO_<chunk> flag, and check info_ptr->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 PNGAPI
png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
{ … }

void PNGAPI
png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
{ … }

/* 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 PNGAPI
png_write_end(png_structrp png_ptr, png_inforp info_ptr)
{ … }

#ifdef PNG_CONVERT_tIME_SUPPORTED
void PNGAPI
png_convert_from_struct_tm(png_timep ptime, const struct tm * ttime)
{
   png_debug(1, "in png_convert_from_struct_tm");

   ptime->year = (png_uint_16)(1900 + ttime->tm_year);
   ptime->month = (png_byte)(ttime->tm_mon + 1);
   ptime->day = (png_byte)ttime->tm_mday;
   ptime->hour = (png_byte)ttime->tm_hour;
   ptime->minute = (png_byte)ttime->tm_min;
   ptime->second = (png_byte)ttime->tm_sec;
}

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

   png_debug(1, "in png_convert_from_time_t");

   tbuf = gmtime(&ttime);
   if (tbuf == NULL)
   {
      /* TODO: add a safe function which takes a png_ptr argument and raises
       * a png_error if the ttime argument is invalid and the call to gmtime
       * fails as a consequence.
       */
      memset(ptime, 0, sizeof(*ptime));
      return;
   }

   png_convert_from_struct_tm(ptime, tbuf);
}
#endif

/* Initialize png_ptr structure, and allocate any memory needed */
PNG_FUNCTION(…)
{ …

/* Alternate initialize png_ptr structure, and allocate any memory needed */
PNG_FUNCTION(png_structp,PNGAPI
png_create_write_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
    png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
{ … }


/* 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 PNGAPI
png_write_rows(png_structrp png_ptr, png_bytepp row,
    png_uint_32 num_rows)
{ … }

/* Write the image.  You only need to call this function once, even
 * if you are writing an interlaced image.
 */
void PNGAPI
png_write_image(png_structrp png_ptr, png_bytepp image)
{ … }

#ifdef PNG_MNG_FEATURES_SUPPORTED
/* Performs intrapixel differencing  */
static void
png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
{
   png_debug(1, "in png_do_write_intrapixel");

   if ((row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
   {
      int bytes_per_pixel;
      png_uint_32 row_width = row_info->width;
      if (row_info->bit_depth == 8)
      {
         png_bytep rp;
         png_uint_32 i;

         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
            bytes_per_pixel = 3;

         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
            bytes_per_pixel = 4;

         else
            return;

         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
         {
            *(rp)     = (png_byte)(*rp       - *(rp + 1));
            *(rp + 2) = (png_byte)(*(rp + 2) - *(rp + 1));
         }
      }

#ifdef PNG_WRITE_16BIT_SUPPORTED
      else if (row_info->bit_depth == 16)
      {
         png_bytep rp;
         png_uint_32 i;

         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
            bytes_per_pixel = 6;

         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
            bytes_per_pixel = 8;

         else
            return;

         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
         {
            png_uint_32 s0   = (png_uint_32)(*(rp    ) << 8) | *(rp + 1);
            png_uint_32 s1   = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
            png_uint_32 s2   = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
            png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);
            png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
            *(rp    ) = (png_byte)(red >> 8);
            *(rp + 1) = (png_byte)red;
            *(rp + 4) = (png_byte)(blue >> 8);
            *(rp + 5) = (png_byte)blue;
         }
      }
#endif /* WRITE_16BIT */
   }
}
#endif /* MNG_FEATURES */

/* Called by user to write a row of image data */
void PNGAPI
png_write_row(png_structrp png_ptr, png_const_bytep row)
{ … }

#ifdef PNG_WRITE_FLUSH_SUPPORTED
/* Set the automatic flush interval or 0 to turn flushing off */
void PNGAPI
png_set_flush(png_structrp png_ptr, int nrows)
{ … }

/* Flush the current output buffers now */
void PNGAPI
png_write_flush(png_structrp png_ptr)
{ … }
#endif /* WRITE_FLUSH */

/* Free any memory used in png_ptr struct without freeing the struct itself. */
static void
png_write_destroy(png_structrp png_ptr)
{ … }

/* Free all memory used by the write.
 * In libpng 1.6.0 this API changed quietly to no longer accept a NULL value for
 * *png_ptr_ptr.  Prior to 1.6.0 it would accept such a value and it would free
 * the passed in info_structs but it would quietly fail to free any of the data
 * inside them.  In 1.6.0 it quietly does nothing (it has to be quiet because it
 * has no png_ptr.)
 */
void PNGAPI
png_destroy_write_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)
{ … }

/* Allow the application to select one or more row filters to use. */
void PNGAPI
png_set_filter(png_structrp png_ptr, int method, int filters)
{ … }

#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* DEPRECATED */
/* Provide floating and fixed point APIs */
#ifdef PNG_FLOATING_POINT_SUPPORTED
void PNGAPI
png_set_filter_heuristics(png_structrp png_ptr, int heuristic_method,
    int num_weights, png_const_doublep filter_weights,
    png_const_doublep filter_costs)
{ … }
#endif /* FLOATING_POINT */

#ifdef PNG_FIXED_POINT_SUPPORTED
void PNGAPI
png_set_filter_heuristics_fixed(png_structrp png_ptr, int heuristic_method,
    int num_weights, png_const_fixed_point_p filter_weights,
    png_const_fixed_point_p filter_costs)
{ … }
#endif /* FIXED_POINT */
#endif /* WRITE_WEIGHTED_FILTER */

#ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
void PNGAPI
png_set_compression_level(png_structrp png_ptr, int level)
{ … }

void PNGAPI
png_set_compression_mem_level(png_structrp png_ptr, int mem_level)
{ … }

void PNGAPI
png_set_compression_strategy(png_structrp png_ptr, int strategy)
{ … }

/* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
 * smaller value of window_bits if it can do so safely.
 */
void PNGAPI
png_set_compression_window_bits(png_structrp png_ptr, int window_bits)
{ … }

void PNGAPI
png_set_compression_method(png_structrp png_ptr, int method)
{ … }
#endif /* WRITE_CUSTOMIZE_COMPRESSION */

/* The following were added to libpng-1.5.4 */
#ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
void PNGAPI
png_set_text_compression_level(png_structrp png_ptr, int level)
{ … }

void PNGAPI
png_set_text_compression_mem_level(png_structrp png_ptr, int mem_level)
{ … }

void PNGAPI
png_set_text_compression_strategy(png_structrp png_ptr, int strategy)
{ … }

/* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
 * smaller value of window_bits if it can do so safely.
 */
void PNGAPI
png_set_text_compression_window_bits(png_structrp png_ptr, int window_bits)
{ … }

void PNGAPI
png_set_text_compression_method(png_structrp png_ptr, int method)
{ … }
#endif /* WRITE_CUSTOMIZE_ZTXT_COMPRESSION */
/* end of API added to libpng-1.5.4 */

void PNGAPI
png_set_write_status_fn(png_structrp png_ptr, png_write_status_ptr write_row_fn)
{ … }

#ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
void PNGAPI
png_set_write_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
    write_user_transform_fn)
{ … }
#endif


#ifdef PNG_INFO_IMAGE_SUPPORTED
void PNGAPI
png_write_png(png_structrp png_ptr, png_inforp info_ptr,
    int transforms, voidp params)
{ … }
#endif


#ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
/* Initialize the write structure - general purpose utility. */
static int
png_image_write_init(png_imagep image)
{ … }

/* Arguments to png_image_write_main: */
png_image_write_control;

/* Write png_uint_16 input to a 16-bit PNG; the png_ptr has already been set to
 * do any necessary byte swapping.  The component order is defined by the
 * png_image format value.
 */
static int
png_write_image_16bit(png_voidp argument)
{ … }

/* Given 16-bit input (1 to 4 channels) write 8-bit output.  If an alpha channel
 * is present it must be removed from the components, the components are then
 * written in sRGB encoding.  No components are added or removed.
 *
 * Calculate an alpha reciprocal to reverse pre-multiplication.  As above the
 * calculation can be done to 15 bits of accuracy; however, the output needs to
 * be scaled in the range 0..255*65535, so include that scaling here.
 */
#define UNP_RECIPROCAL(alpha) …

static png_byte
png_unpremultiply(png_uint_32 component, png_uint_32 alpha,
    png_uint_32 reciprocal/*from the above macro*/)
{ … }

static int
png_write_image_8bit(png_voidp argument)
{ … }

static void
png_image_set_PLTE(png_image_write_control *display)
{ … }

static int
png_image_write_main(png_voidp argument)
{ … }


static void (PNGCBAPI
image_memory_write)(png_structp png_ptr, png_bytep/*const*/ data, size_t size)
{ … }

static void (PNGCBAPI
image_memory_flush)(png_structp png_ptr)
{ … }

static int
png_image_write_memory(png_voidp argument)
{ … }

int PNGAPI
png_image_write_to_memory(png_imagep image, void *memory,
    png_alloc_size_t * PNG_RESTRICT memory_bytes, int convert_to_8bit,
    const void *buffer, png_int_32 row_stride, const void *colormap)
{ … }

#ifdef PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED
int PNGAPI
png_image_write_to_stdio(png_imagep image, FILE *file, int convert_to_8bit,
    const void *buffer, png_int_32 row_stride, const void *colormap)
{ … }

int PNGAPI
png_image_write_to_file(png_imagep image, const char *file_name,
    int convert_to_8bit, const void *buffer, png_int_32 row_stride,
    const void *colormap)
{ … }
#endif /* SIMPLIFIED_WRITE_STDIO */
#endif /* SIMPLIFIED_WRITE */
#endif /* WRITE */