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pngwrite.c
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/* pngwrite.c - general routines to write a PNG file
*
* Copyright (c) 2018-2025 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)
{
if (info_ptr->unknown_chunks_num != 0)
{
png_const_unknown_chunkp up;
png_debug(5, "writing extra chunks");
for (up = info_ptr->unknown_chunks;
up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
++up)
if ((up->location & where) != 0)
{
/* If per-chunk unknown chunk handling is enabled use it, otherwise
* just write the chunks the application has set.
*/
#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
int keep = png_handle_as_unknown(png_ptr, up->name);
/* NOTE: this code is radically different from the read side in the
* matter of handling an ancillary unknown chunk. In the read side
* the default behavior is to discard it, in the code below the default
* behavior is to write it. Critical chunks are, however, only
* written if explicitly listed or if the default is set to write all
* unknown chunks.
*
* The default handling is also slightly weird - it is not possible to
* stop the writing of all unsafe-to-copy chunks!
*
* TODO: REVIEW: this would seem to be a bug.
*/
if (keep != PNG_HANDLE_CHUNK_NEVER &&
((up->name[3] & 0x20) /* safe-to-copy overrides everything */ ||
keep == PNG_HANDLE_CHUNK_ALWAYS ||
(keep == PNG_HANDLE_CHUNK_AS_DEFAULT &&
png_ptr->unknown_default == PNG_HANDLE_CHUNK_ALWAYS)))
#endif
{
/* TODO: review, what is wrong with a zero length unknown chunk? */
if (up->size == 0)
png_warning(png_ptr, "Writing zero-length unknown chunk");
png_write_chunk(png_ptr, up->name, up->data, up->size);
}
}
}
}
#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)
{
png_debug(1, "in png_write_info_before_PLTE");
if (png_ptr == NULL || info_ptr == NULL)
return;
if ((png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE) == 0)
{
/* Write PNG signature */
png_write_sig(png_ptr);
#ifdef PNG_MNG_FEATURES_SUPPORTED
if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \
png_ptr->mng_features_permitted != 0)
{
png_warning(png_ptr,
"MNG features are not allowed in a PNG datastream");
png_ptr->mng_features_permitted = 0;
}
#endif
/* Write IHDR information. */
png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
info_ptr->filter_type,
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
info_ptr->interlace_type
#else
0
#endif
);
/* The rest of these check to see if the valid field has the appropriate
* flag set, and if it does, writes the chunk.
*
* 1.6.0: COLORSPACE support controls the writing of these chunks too, and
* the chunks will be written if the WRITE routine is there and
* information * is available in the COLORSPACE. (See
* png_colorspace_sync_info in png.c for where the valid flags get set.)
*
* Under certain circumstances the colorspace can be invalidated without
* syncing the info_struct 'valid' flags; this happens if libpng detects
* an error and calls png_error while the color space is being set, yet
* the application continues writing the PNG. So check the 'invalid'
* flag here too.
*/
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
/* Write unknown chunks first; PNG v3 establishes a precedence order
* for colourspace chunks. It is certain therefore that new
* colourspace chunks will have a precedence and very likely it will be
* higher than all known so far. Writing the unknown chunks here is
* most likely to present the chunks in the most convenient order.
*
* FUTURE: maybe write chunks in the order the app calls png_set_chnk
* to give the app control.
*/
write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
#endif
#ifdef PNG_WRITE_sBIT_SUPPORTED
/* PNG v3: a streaming app will need to see this before cICP because
* the information is helpful in handling HLG encoding (which is
* natively 10 bits but gets expanded to 16 in PNG.)
*
* The app shouldn't care about the order ideally, but it might have
* no choice. In PNG v3, apps are allowed to reject PNGs where the
* APNG chunks are out of order so it behooves libpng to be nice here.
*/
if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
#endif
/* PNG v3: the July 2004 version of the TR introduced the concept of colour
* space priority. As above it therefore behooves libpng to write the colour
* space chunks in the priority order so that a streaming app need not buffer
* them.
*
* PNG v3: Chunks mDCV and cLLI provide ancillary information for the
* interpretation of the colourspace chunkgs but do not require support for
* those chunks so are outside the "COLORSPACE" check but before the write of
* the colourspace chunks themselves.
*/
#ifdef PNG_WRITE_cLLI_SUPPORTED
if ((info_ptr->valid & PNG_INFO_cLLI) != 0)
{
png_write_cLLI_fixed(png_ptr, info_ptr->maxCLL, info_ptr->maxFALL);
}
#endif
#ifdef PNG_WRITE_mDCV_SUPPORTED
if ((info_ptr->valid & PNG_INFO_mDCV) != 0)
{
png_write_mDCV_fixed(png_ptr,
info_ptr->mastering_red_x, info_ptr->mastering_red_y,
info_ptr->mastering_green_x, info_ptr->mastering_green_y,
info_ptr->mastering_blue_x, info_ptr->mastering_blue_y,
info_ptr->mastering_white_x, info_ptr->mastering_white_y,
info_ptr->mastering_maxDL, info_ptr->mastering_minDL);
}
#endif
#ifdef PNG_COLORSPACE_SUPPORTED
# ifdef PNG_WRITE_cICP_SUPPORTED /* Priority 4 */
if ((info_ptr->valid & PNG_INFO_cICP) != 0)
{
png_write_cICP(png_ptr,
info_ptr->cicp_colour_primaries,
info_ptr->cicp_transfer_function,
info_ptr->cicp_matrix_coefficients,
info_ptr->cicp_video_full_range_flag);
}
# endif
/* PNG v3 change: it is now permitted to write both sRGB and ICC profiles,
* however because the libpng code auto-generates an sRGB for the
* corresponding ICC profiles and because PNG v2 disallowed this we need
* to only write one.
*
* Remove the PNG v2 warning about writing an sRGB ICC profile as well
* because it's invalid with PNG v3.
*/
# ifdef PNG_WRITE_iCCP_SUPPORTED /* Priority 3 */
if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
(info_ptr->valid & PNG_INFO_iCCP) != 0)
{
png_write_iCCP(png_ptr, info_ptr->iccp_name,
info_ptr->iccp_profile);
}
# ifdef PNG_WRITE_sRGB_SUPPORTED
else
# endif
# endif
# ifdef PNG_WRITE_sRGB_SUPPORTED /* Priority 2 */
if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
(info_ptr->valid & PNG_INFO_sRGB) != 0)
png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
# endif /* WRITE_sRGB */
#endif /* COLORSPACE */
#ifdef PNG_GAMMA_SUPPORTED
# ifdef PNG_WRITE_gAMA_SUPPORTED /* Priority 1 */
if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_gAMA) != 0 &&
(info_ptr->valid & PNG_INFO_gAMA) != 0)
png_write_gAMA_fixed(png_ptr, info_ptr->colorspace.gamma);
# endif
#endif
#ifdef PNG_COLORSPACE_SUPPORTED
# ifdef PNG_WRITE_cHRM_SUPPORTED /* Also priority 1 */
if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
(info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&
(info_ptr->valid & PNG_INFO_cHRM) != 0)
png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
# endif
#endif
png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;
}
}
void PNGAPI
png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
{
#if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
int i;
#endif
png_debug(1, "in png_write_info");
if (png_ptr == NULL || info_ptr == NULL)
return;
png_write_info_before_PLTE(png_ptr, info_ptr);
if ((info_ptr->valid & PNG_INFO_PLTE) != 0)
png_write_PLTE(png_ptr, info_ptr->palette,
(png_uint_32)info_ptr->num_palette);
else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
png_error(png_ptr, "Valid palette required for paletted images");
#ifdef PNG_WRITE_tRNS_SUPPORTED
if ((info_ptr->valid & PNG_INFO_tRNS) !=0)
{
#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
/* Invert the alpha channel (in tRNS) */
if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0 &&
info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
{
int j, jend;
jend = info_ptr->num_trans;
if (jend > PNG_MAX_PALETTE_LENGTH)
jend = PNG_MAX_PALETTE_LENGTH;
for (j = 0; j<jend; ++j)
info_ptr->trans_alpha[j] =
(png_byte)(255 - info_ptr->trans_alpha[j]);
}
#endif
png_write_tRNS(png_ptr, info_ptr->trans_alpha, &(info_ptr->trans_color),
info_ptr->num_trans, info_ptr->color_type);
}
#endif
#ifdef PNG_WRITE_bKGD_SUPPORTED
if ((info_ptr->valid & PNG_INFO_bKGD) != 0)
png_write_bKGD(png_ptr, &(info_ptr->background), info_ptr->color_type);
#endif
#ifdef PNG_WRITE_eXIf_SUPPORTED
if ((info_ptr->valid & PNG_INFO_eXIf) != 0)
{
png_write_eXIf(png_ptr, info_ptr->exif, info_ptr->num_exif);
png_ptr->mode |= PNG_WROTE_eXIf;
}
#endif
#ifdef PNG_WRITE_hIST_SUPPORTED
if ((info_ptr->valid & PNG_INFO_hIST) != 0)
png_write_hIST(png_ptr, info_ptr->hist, info_ptr->num_palette);
#endif
#ifdef PNG_WRITE_oFFs_SUPPORTED
if ((info_ptr->valid & PNG_INFO_oFFs) != 0)
png_write_oFFs(png_ptr, info_ptr->x_offset, info_ptr->y_offset,
info_ptr->offset_unit_type);
#endif
#ifdef PNG_WRITE_pCAL_SUPPORTED
if ((info_ptr->valid & PNG_INFO_pCAL) != 0)
png_write_pCAL(png_ptr, info_ptr->pcal_purpose, info_ptr->pcal_X0,
info_ptr->pcal_X1, info_ptr->pcal_type, info_ptr->pcal_nparams,
info_ptr->pcal_units, info_ptr->pcal_params);
#endif
#ifdef PNG_WRITE_sCAL_SUPPORTED
if ((info_ptr->valid & PNG_INFO_sCAL) != 0)
png_write_sCAL_s(png_ptr, (int)info_ptr->scal_unit,
info_ptr->scal_s_width, info_ptr->scal_s_height);
#endif /* sCAL */
#ifdef PNG_WRITE_pHYs_SUPPORTED
if ((info_ptr->valid & PNG_INFO_pHYs) != 0)
png_write_pHYs(png_ptr, info_ptr->x_pixels_per_unit,
info_ptr->y_pixels_per_unit, info_ptr->phys_unit_type);
#endif /* pHYs */
#ifdef PNG_WRITE_tIME_SUPPORTED
if ((info_ptr->valid & PNG_INFO_tIME) != 0)
{
png_write_tIME(png_ptr, &(info_ptr->mod_time));
png_ptr->mode |= PNG_WROTE_tIME;
}
#endif /* tIME */
#ifdef PNG_WRITE_sPLT_SUPPORTED
if ((info_ptr->valid & PNG_INFO_sPLT) != 0)
for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
png_write_sPLT(png_ptr, info_ptr->splt_palettes + i);
#endif /* sPLT */
#ifdef PNG_WRITE_TEXT_SUPPORTED
/* Check to see if we need to write text chunks */
for (i = 0; i < info_ptr->num_text; i++)
{
png_debug2(2, "Writing header text chunk %d, type %d", i,
info_ptr->text[i].compression);
/* An internationalized chunk? */
if (info_ptr->text[i].compression > 0)
{
#ifdef PNG_WRITE_iTXt_SUPPORTED
/* Write international chunk */
png_write_iTXt(png_ptr,
info_ptr->text[i].compression,
info_ptr->text[i].key,
info_ptr->text[i].lang,
info_ptr->text[i].lang_key,
info_ptr->text[i].text);
/* Mark this chunk as written */
if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
else
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
png_warning(png_ptr, "Unable to write international text");
#endif
}
/* If we want a compressed text chunk */
else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_zTXt)
{
#ifdef PNG_WRITE_zTXt_SUPPORTED
/* Write compressed chunk */
png_write_zTXt(png_ptr, info_ptr->text[i].key,
info_ptr->text[i].text, info_ptr->text[i].compression);
/* Mark this chunk as written */
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
png_warning(png_ptr, "Unable to write compressed text");
#endif
}
else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
{
#ifdef PNG_WRITE_tEXt_SUPPORTED
/* Write uncompressed chunk */
png_write_tEXt(png_ptr, info_ptr->text[i].key,
info_ptr->text[i].text,
0);
/* Mark this chunk as written */
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
#else
/* Can't get here */
png_warning(png_ptr, "Unable to write uncompressed text");
#endif
}
}
#endif /* tEXt */
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_PLTE);
#endif
}
/* 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)
{
png_debug(1, "in png_write_end");
if (png_ptr == NULL)
return;
if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
png_error(png_ptr, "No IDATs written into file");
#ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
png_ptr->num_palette_max >= png_ptr->num_palette)
png_benign_error(png_ptr, "Wrote palette index exceeding num_palette");
#endif
/* See if user wants us to write information chunks */
if (info_ptr != NULL)
{
#ifdef PNG_WRITE_TEXT_SUPPORTED
int i; /* local index variable */
#endif
#ifdef PNG_WRITE_tIME_SUPPORTED
/* Check to see if user has supplied a time chunk */
if ((info_ptr->valid & PNG_INFO_tIME) != 0 &&
(png_ptr->mode & PNG_WROTE_tIME) == 0)
png_write_tIME(png_ptr, &(info_ptr->mod_time));
#endif
#ifdef PNG_WRITE_TEXT_SUPPORTED
/* Loop through comment chunks */
for (i = 0; i < info_ptr->num_text; i++)
{
png_debug2(2, "Writing trailer text chunk %d, type %d", i,
info_ptr->text[i].compression);
/* An internationalized chunk? */
if (info_ptr->text[i].compression > 0)
{
#ifdef PNG_WRITE_iTXt_SUPPORTED
/* Write international chunk */
png_write_iTXt(png_ptr,
info_ptr->text[i].compression,
info_ptr->text[i].key,
info_ptr->text[i].lang,
info_ptr->text[i].lang_key,
info_ptr->text[i].text);
/* Mark this chunk as written */
if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
else
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
png_warning(png_ptr, "Unable to write international text");
#endif
}
else if (info_ptr->text[i].compression >= PNG_TEXT_COMPRESSION_zTXt)
{
#ifdef PNG_WRITE_zTXt_SUPPORTED
/* Write compressed chunk */
png_write_zTXt(png_ptr, info_ptr->text[i].key,
info_ptr->text[i].text, info_ptr->text[i].compression);
/* Mark this chunk as written */
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
png_warning(png_ptr, "Unable to write compressed text");
#endif
}
else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
{
#ifdef PNG_WRITE_tEXt_SUPPORTED
/* Write uncompressed chunk */
png_write_tEXt(png_ptr, info_ptr->text[i].key,
info_ptr->text[i].text, 0);
/* Mark this chunk as written */
info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
#else
png_warning(png_ptr, "Unable to write uncompressed text");
#endif
}
}
#endif
#ifdef PNG_WRITE_eXIf_SUPPORTED
if ((info_ptr->valid & PNG_INFO_eXIf) != 0 &&
(png_ptr->mode & PNG_WROTE_eXIf) == 0)
png_write_eXIf(png_ptr, info_ptr->exif, info_ptr->num_exif);
#endif
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
write_unknown_chunks(png_ptr, info_ptr, PNG_AFTER_IDAT);
#endif
}
png_ptr->mode |= PNG_AFTER_IDAT;
/* Write end of PNG file */
png_write_IEND(png_ptr);
/* This flush, added in libpng-1.0.8, removed from libpng-1.0.9beta03,
* and restored again in libpng-1.2.30, may cause some applications that
* do not set png_ptr->output_flush_fn to crash. If your application
* experiences a problem, please try building libpng with
* PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED defined, and report the event to
* png-mng-implement at lists.sf.net .
*/
#ifdef PNG_WRITE_FLUSH_SUPPORTED
# ifdef PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED
png_flush(png_ptr);
# endif
#endif
}
#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(png_structp,PNGAPI
png_create_write_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
{
#ifndef PNG_USER_MEM_SUPPORTED
png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
error_fn, warn_fn, NULL, NULL, NULL);
#else
return png_create_write_struct_2(user_png_ver, error_ptr, error_fn,
warn_fn, NULL, NULL, NULL);
}
/* 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)
{
png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
#endif /* USER_MEM */
if (png_ptr != NULL)
{
/* Set the zlib control values to defaults; they can be overridden by the
* application after the struct has been created.
*/
png_ptr->zbuffer_size = PNG_ZBUF_SIZE;
/* The 'zlib_strategy' setting is irrelevant because png_default_claim in
* pngwutil.c defaults it according to whether or not filters will be
* used, and ignores this setting.
*/
png_ptr->zlib_strategy = PNG_Z_DEFAULT_STRATEGY;
png_ptr->zlib_level = PNG_Z_DEFAULT_COMPRESSION;
png_ptr->zlib_mem_level = 8;
png_ptr->zlib_window_bits = 15;
png_ptr->zlib_method = 8;
#ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
png_ptr->zlib_text_strategy = PNG_TEXT_Z_DEFAULT_STRATEGY;
png_ptr->zlib_text_level = PNG_TEXT_Z_DEFAULT_COMPRESSION;
png_ptr->zlib_text_mem_level = 8;
png_ptr->zlib_text_window_bits = 15;
png_ptr->zlib_text_method = 8;
#endif /* WRITE_COMPRESSED_TEXT */
/* This is a highly dubious configuration option; by default it is off,
* but it may be appropriate for private builds that are testing
* extensions not conformant to the current specification, or of
* applications that must not fail to write at all costs!
*/
#ifdef PNG_BENIGN_WRITE_ERRORS_SUPPORTED
/* In stable builds only warn if an application error can be completely
* handled.
*/
png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
#endif
/* App warnings are warnings in release (or release candidate) builds but
* are errors during development.
*/
#if PNG_RELEASE_BUILD
png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
#endif
/* TODO: delay this, it can be done in png_init_io() (if the app doesn't
* do it itself) avoiding setting the default function if it is not
* required.
*/
png_set_write_fn(png_ptr, NULL, NULL, NULL);
}
return png_ptr;
}
/* 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)
{
png_uint_32 i; /* row counter */
png_bytepp rp; /* row pointer */
png_debug(1, "in png_write_rows");
if (png_ptr == NULL)
return;
/* 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 PNGAPI
png_write_image(png_structrp png_ptr, png_bytepp image)
{
png_uint_32 i; /* row index */
int pass, num_pass; /* pass variables */
png_bytepp rp; /* points to current row */
if (png_ptr == NULL)
return;
png_debug(1, "in png_write_image");
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
/* Initialize interlace handling. If image is not interlaced,
* this will set pass to 1
*/
num_pass = png_set_interlace_handling(png_ptr);
#else
num_pass = 1;
#endif
/* 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);
}
}
}
#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)
{
/* 1.5.6: moved from png_struct to be a local structure: */
png_row_info row_info;
png_debug2(1, "in png_write_row (row %u, pass %d)",
png_ptr->row_number, png_ptr->pass);
if (png_ptr == NULL)
return;
/* Initialize transformations and other stuff if first time */
if (png_ptr->row_number == 0 && png_ptr->pass == 0)
{
/* Make sure we wrote the header info */
if ((png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE) == 0)
png_error(png_ptr,
"png_write_info was never called before png_write_row");
/* Check for transforms that have been set but were defined out */
#if !defined(PNG_WRITE_INVERT_SUPPORTED) && defined(PNG_READ_INVERT_SUPPORTED)
if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
png_warning(png_ptr, "PNG_WRITE_INVERT_SUPPORTED is not defined");
#endif
#if !defined(PNG_WRITE_FILLER_SUPPORTED) && defined(PNG_READ_FILLER_SUPPORTED)
if ((png_ptr->transformations & PNG_FILLER) != 0)
png_warning(png_ptr, "PNG_WRITE_FILLER_SUPPORTED is not defined");
#endif
#if !defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
defined(PNG_READ_PACKSWAP_SUPPORTED)
if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
png_warning(png_ptr,
"PNG_WRITE_PACKSWAP_SUPPORTED is not defined");
#endif
#if !defined(PNG_WRITE_PACK_SUPPORTED) && defined(PNG_READ_PACK_SUPPORTED)
if ((png_ptr->transformations & PNG_PACK) != 0)
png_warning(png_ptr, "PNG_WRITE_PACK_SUPPORTED is not defined");
#endif
#if !defined(PNG_WRITE_SHIFT_SUPPORTED) && defined(PNG_READ_SHIFT_SUPPORTED)
if ((png_ptr->transformations & PNG_SHIFT) != 0)
png_warning(png_ptr, "PNG_WRITE_SHIFT_SUPPORTED is not defined");
#endif
#if !defined(PNG_WRITE_BGR_SUPPORTED) && defined(PNG_READ_BGR_SUPPORTED)
if ((png_ptr->transformations & PNG_BGR) != 0)
png_warning(png_ptr, "PNG_WRITE_BGR_SUPPORTED is not defined");
#endif
#if !defined(PNG_WRITE_SWAP_SUPPORTED) && defined(PNG_READ_SWAP_SUPPORTED)
if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
png_warning(png_ptr, "PNG_WRITE_SWAP_SUPPORTED is not defined");
#endif
png_write_start_row(png_ptr);
}
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
/* If interlaced and not interested in row, return */
if (png_ptr->interlaced != 0 &&
(png_ptr->transformations & PNG_INTERLACE) != 0)
{
switch (png_ptr->pass)
{
case 0:
if ((png_ptr->row_number & 0x07) != 0)
{
png_write_finish_row(png_ptr);
return;
}
break;
case 1:
if ((png_ptr->row_number & 0x07) != 0 || png_ptr->width < 5)
{
png_write_finish_row(png_ptr);
return;
}
break;
case 2:
if ((png_ptr->row_number & 0x07) != 4)
{
png_write_finish_row(png_ptr);
return;
}
break;
case 3:
if ((png_ptr->row_number & 0x03) != 0 || png_ptr->width < 3)
{
png_write_finish_row(png_ptr);
return;
}
break;
case 4:
if ((png_ptr->row_number & 0x03) != 2)
{
png_write_finish_row(png_ptr);
return;
}
break;
case 5:
if ((png_ptr->row_number & 0x01) != 0 || png_ptr->width < 2)
{
png_write_finish_row(png_ptr);
return;
}
break;
case 6:
if ((png_ptr->row_number & 0x01) == 0)
{
png_write_finish_row(png_ptr);
return;
}
break;
default: /* error: ignore it */
break;
}
}
#endif
/* Set up row info for transformations */
row_info.color_type = png_ptr->color_type;
row_info.width = png_ptr->usr_width;
row_info.channels = png_ptr->usr_channels;
row_info.bit_depth = png_ptr->usr_bit_depth;
row_info.pixel_depth = (png_byte)(row_info.bit_depth * row_info.channels);
row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
png_debug1(3, "row_info->color_type = %d", row_info.color_type);
png_debug1(3, "row_info->width = %u", row_info.width);
png_debug1(3, "row_info->channels = %d", row_info.channels);
png_debug1(3, "row_info->bit_depth = %d", row_info.bit_depth);
png_debug1(3, "row_info->pixel_depth = %d", row_info.pixel_depth);
png_debug1(3, "row_info->rowbytes = %lu", (unsigned long)row_info.rowbytes);
/* Copy user's row into buffer, leaving room for filter byte. */
memcpy(png_ptr->row_buf + 1, row, row_info.rowbytes);
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
/* Handle interlacing */
if (png_ptr->interlaced && png_ptr->pass < 6 &&
(png_ptr->transformations & PNG_INTERLACE) != 0)
{
png_do_write_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass);
/* This should always get caught above, but still ... */
if (row_info.width == 0)
{
png_write_finish_row(png_ptr);
return;
}
}
#endif
#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
/* Handle other transformations */
if (png_ptr->transformations != 0)
png_do_write_transformations(png_ptr, &row_info);
#endif
/* At this point the row_info pixel depth must match the 'transformed' depth,
* which is also the output depth.
*/
if (row_info.pixel_depth != png_ptr->pixel_depth ||
row_info.pixel_depth != png_ptr->transformed_pixel_depth)
png_error(png_ptr, "internal write transform logic error");
#ifdef PNG_MNG_FEATURES_SUPPORTED
/* Write filter_method 64 (intrapixel differencing) only if
* 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
* 2. Libpng did not write a PNG signature (this filter_method is only
* used in PNG datastreams that are embedded in MNG datastreams) and
* 3. The application called png_permit_mng_features with a mask that
* included PNG_FLAG_MNG_FILTER_64 and
* 4. The filter_method is 64 and
* 5. The color_type is RGB or RGBA
*/
if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
(png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
{
/* Intrapixel differencing */
png_do_write_intrapixel(&row_info, png_ptr->row_buf + 1);
}
#endif
/* Added at libpng-1.5.10 */
#ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
/* Check for out-of-range palette index */
if (row_info.color_type == PNG_COLOR_TYPE_PALETTE &&
png_ptr->num_palette_max >= 0)
png_do_check_palette_indexes(png_ptr, &row_info);
#endif
/* Find a filter if necessary, filter the row and write it out. */
png_write_find_filter(png_ptr, &row_info);
if (png_ptr->write_row_fn != NULL)
(*(png_ptr->write_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
}
#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)
{
png_debug(1, "in png_set_flush");
if (png_ptr == NULL)
return;
png_ptr->flush_dist = (nrows < 0 ? 0 : (png_uint_32)nrows);
}
/* Flush the current output buffers now */
void PNGAPI
png_write_flush(png_structrp png_ptr)
{
png_debug(1, "in png_write_flush");
if (png_ptr == NULL)
return;
/* We have already written out all of the data */
if (png_ptr->row_number >= png_ptr->num_rows)
return;
png_compress_IDAT(png_ptr, NULL, 0, Z_SYNC_FLUSH);