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mapnik/include/mapnik/png_io.hpp

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/*****************************************************************************
*
* This file is part of Mapnik (c++ mapping toolkit)
*
* Copyright (C) 2021 Artem Pavlenko
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*****************************************************************************/
#ifndef MAPNIK_PNG_IO_HPP
#define MAPNIK_PNG_IO_HPP
// mapnik
#include <mapnik/palette.hpp>
#include <mapnik/octree.hpp>
#include <mapnik/hextree.hpp>
#include <mapnik/image.hpp>
#include <mapnik/warning.hpp>
MAPNIK_DISABLE_WARNING_PUSH
#include <mapnik/warning_ignore.hpp>
// zlib
#include <zlib.h> // for Z_DEFAULT_COMPRESSION
extern "C" {
#include <png.h>
}
#include <set>
#include <string>
MAPNIK_DISABLE_WARNING_POP
#define MAX_OCTREE_LEVELS 4
namespace mapnik {
struct png_options
{
int colors;
int filters;
int compression;
int strategy;
int trans_mode;
double gamma;
bool paletted;
bool use_hextree;
png_options()
: colors(256)
, filters(PNG_FILTER_NONE)
, compression(Z_DEFAULT_COMPRESSION)
, strategy(Z_DEFAULT_STRATEGY)
, trans_mode(-1)
, gamma(-1)
, paletted(true)
, use_hextree(true)
{}
};
template<typename T>
void write_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
T* out = static_cast<T*>(png_get_io_ptr(png_ptr));
out->write(reinterpret_cast<char*>(data), length);
}
template<typename T>
void flush_data(png_structp png_ptr)
{
T* out = static_cast<T*>(png_get_io_ptr(png_ptr));
out->flush();
}
template<typename T1, typename T2>
void save_as_png(T1& file, T2 const& image, png_options const& opts)
{
png_voidp error_ptr = 0;
png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, error_ptr, 0, 0);
if (!png_ptr)
return;
// switch on optimization only if supported
#if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200) && defined(PNG_MMX_CODE_SUPPORTED)
png_uint_32 mask, flags;
flags = png_get_asm_flags(png_ptr);
mask = png_get_asm_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE);
png_set_asm_flags(png_ptr, flags | mask);
#endif
png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, opts.filters);
png_infop info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
{
png_destroy_write_struct(&png_ptr, static_cast<png_infopp>(0));
return;
}
jmp_buf* jmp_context = static_cast<jmp_buf*>(png_get_error_ptr(png_ptr));
if (jmp_context)
{
png_destroy_write_struct(&png_ptr, &info_ptr);
return;
}
png_set_write_fn(png_ptr, &file, &write_data<T1>, &flush_data<T1>);
png_set_compression_level(png_ptr, opts.compression);
png_set_compression_strategy(png_ptr, opts.strategy);
png_set_compression_buffer_size(png_ptr, 32768);
png_set_IHDR(png_ptr,
info_ptr,
image.width(),
image.height(),
8,
(opts.trans_mode == 0) ? PNG_COLOR_TYPE_RGB : PNG_COLOR_TYPE_RGB_ALPHA,
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
const std::unique_ptr<png_bytep[]> row_pointers(new png_bytep[image.height()]);
for (unsigned int i = 0; i < image.height(); ++i)
{
row_pointers[i] = const_cast<png_bytep>(reinterpret_cast<const unsigned char*>(image.get_row(i)));
}
png_set_rows(png_ptr, info_ptr, row_pointers.get());
png_write_png(png_ptr,
info_ptr,
(opts.trans_mode == 0) ? PNG_TRANSFORM_STRIP_FILLER_AFTER : PNG_TRANSFORM_IDENTITY,
nullptr);
png_destroy_write_struct(&png_ptr, &info_ptr);
}
template<typename T>
void reduce_8(T const& in,
image_gray8& out,
octree<rgb> trees[],
unsigned limits[],
unsigned levels,
std::vector<unsigned>& alpha)
{
unsigned width = in.width();
unsigned height = in.height();
std::vector<unsigned> alphaCount(alpha.size());
for (unsigned i = 0; i < alpha.size(); ++i)
{
alpha[i] = 0;
alphaCount[i] = 0;
}
for (unsigned y = 0; y < height; ++y)
{
mapnik::image_rgba8::pixel_type const* row = in.get_row(y);
mapnik::image_gray8::pixel_type* row_out = out.get_row(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
std::uint8_t index = 0;
int idx = -1;
for (int j = levels - 1; j > 0; --j)
{
if (U2ALPHA(val) >= limits[j] && trees[j].colors() > 0)
{
index = idx = trees[j].quantize(val);
break;
}
}
if (idx >= 0 && idx < static_cast<int>(alpha.size()))
{
alpha[idx] += U2ALPHA(val);
++alphaCount[idx];
}
row_out[x] = index;
}
}
for (unsigned i = 0; i < alpha.size(); ++i)
{
if (alphaCount[i] != 0)
{
alpha[i] /= alphaCount[i];
}
}
}
template<typename T>
void reduce_4(T const& in,
image_gray8& out,
octree<rgb> trees[],
unsigned limits[],
unsigned levels,
std::vector<unsigned>& alpha)
{
unsigned width = in.width();
unsigned height = in.height();
std::vector<unsigned> alphaCount(alpha.size());
for (unsigned i = 0; i < alpha.size(); ++i)
{
alpha[i] = 0;
alphaCount[i] = 0;
}
for (unsigned y = 0; y < height; ++y)
{
mapnik::image_rgba8::pixel_type const* row = in.get_row(y);
mapnik::image_gray8::pixel_type* row_out = out.get_row(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
std::uint8_t index = 0;
int idx = -1;
for (int j = levels - 1; j > 0; --j)
{
if (U2ALPHA(val) >= limits[j] && trees[j].colors() > 0)
{
index = idx = trees[j].quantize(val);
break;
}
}
if (idx >= 0 && idx < static_cast<int>(alpha.size()))
{
alpha[idx] += U2ALPHA(val);
++alphaCount[idx];
}
if (x % 2 == 0)
{
index = index << 4;
}
row_out[x >> 1] |= index;
}
}
for (unsigned i = 0; i < alpha.size(); ++i)
{
if (alphaCount[i] != 0)
{
alpha[i] /= alphaCount[i];
}
}
}
// 1-bit but only one color.
template<typename T>
void reduce_1(T const&,
image_gray8& out,
octree<rgb> /*trees*/[],
unsigned /*limits*/[],
std::vector<unsigned>& /*alpha*/)
{
out.set(0); // only one color!!!
}
template<typename T>
void save_as_png(T& file,
std::vector<mapnik::rgb> const& palette,
mapnik::image_gray8 const& image,
unsigned width,
unsigned height,
unsigned color_depth,
std::vector<unsigned> const& alpha,
png_options const& opts)
{
png_voidp error_ptr = 0;
png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, error_ptr, 0, 0);
if (!png_ptr)
{
return;
}
// switch on optimization only if supported
#if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200) && defined(PNG_MMX_CODE_SUPPORTED)
png_uint_32 mask, flags;
flags = png_get_asm_flags(png_ptr);
mask = png_get_asm_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE);
png_set_asm_flags(png_ptr, flags | mask);
#endif
png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, opts.filters);
png_infop info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
{
png_destroy_write_struct(&png_ptr, static_cast<png_infopp>(0));
return;
}
jmp_buf* jmp_context = static_cast<jmp_buf*>(png_get_error_ptr(png_ptr));
if (jmp_context)
{
png_destroy_write_struct(&png_ptr, &info_ptr);
return;
}
png_set_write_fn(png_ptr, &file, &write_data<T>, &flush_data<T>);
png_set_compression_level(png_ptr, opts.compression);
png_set_compression_strategy(png_ptr, opts.strategy);
png_set_compression_buffer_size(png_ptr, 32768);
png_set_IHDR(png_ptr,
info_ptr,
width,
height,
color_depth,
PNG_COLOR_TYPE_PALETTE,
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
png_color* pal = const_cast<png_color*>(reinterpret_cast<const png_color*>(&palette[0]));
png_set_PLTE(png_ptr, info_ptr, pal, static_cast<unsigned>(palette.size()));
// make transparent lowest indexes, so tRNS is small
if (alpha.size() > 0)
{
std::vector<png_byte> trans(alpha.size());
unsigned alphaSize = 0; // truncate to nonopaque values
for (unsigned i = 0; i < alpha.size(); ++i)
{
trans[i] = alpha[i];
if (alpha[i] < 255)
{
alphaSize = i + 1;
}
}
if (alphaSize > 0)
{
png_set_tRNS(png_ptr, info_ptr, static_cast<png_bytep>(&trans[0]), alphaSize, 0);
}
}
png_write_info(png_ptr, info_ptr);
for (unsigned i = 0; i < height; ++i)
{
png_write_row(png_ptr, const_cast<png_bytep>(image.get_row(i)));
}
png_write_end(png_ptr, info_ptr);
png_destroy_write_struct(&png_ptr, &info_ptr);
}
template<typename T1, typename T2>
void save_as_png8_oct(T1& file, T2 const& image, png_options const& opts)
{
// number of alpha ranges in png8 format; 2 results in smallest image with binary transparency
// 3 is minimum for semitransparency, 4 is recommended, anything else is worse
const unsigned TRANSPARENCY_LEVELS = (opts.trans_mode == 2 || opts.trans_mode < 0) ? MAX_OCTREE_LEVELS : 2;
unsigned width = image.width();
unsigned height = image.height();
unsigned alphaHist[256]; // transparency histogram
unsigned semiCount = 0; // sum of semitransparent pixels
unsigned meanAlpha = 0;
if (opts.trans_mode == 0)
{
meanAlpha = 255;
}
else
{
for (int i = 0; i < 256; ++i)
{
alphaHist[i] = 0;
}
for (unsigned y = 0; y < height; ++y)
{
for (unsigned x = 0; x < width; ++x)
{
unsigned val = U2ALPHA(static_cast<unsigned>(image.get_row(y)[x]));
++alphaHist[val];
meanAlpha += val;
if (val > 0 && val < 255)
{
++semiCount;
}
}
}
meanAlpha /= width * height;
}
// transparency ranges division points
unsigned limits[MAX_OCTREE_LEVELS + 1];
limits[0] = 0;
limits[1] = (opts.trans_mode != 0 && alphaHist[0] > 0) ? 1 : 0;
limits[TRANSPARENCY_LEVELS] = 256;
for (unsigned j = 2; j < TRANSPARENCY_LEVELS; ++j)
{
limits[j] = limits[1];
}
if (opts.trans_mode != 0)
{
unsigned alphaHistSum = 0;
for (unsigned i = 1; i < 256; ++i)
{
alphaHistSum += alphaHist[i];
for (unsigned j = 1; j < TRANSPARENCY_LEVELS; ++j)
{
if (alphaHistSum < semiCount * (j) / 4)
{
limits[j] = i;
}
}
}
}
// avoid too wide full transparent range
if (limits[1] > 256 / (TRANSPARENCY_LEVELS - 1))
{
limits[1] = 256 / (TRANSPARENCY_LEVELS - 1);
}
// avoid too wide full opaque range
if (limits[TRANSPARENCY_LEVELS - 1] < 212)
{
limits[TRANSPARENCY_LEVELS - 1] = 212;
}
if (TRANSPARENCY_LEVELS == 2)
{
limits[1] = 127;
}
// estimated number of colors from palette assigned to chosen ranges
unsigned cols[MAX_OCTREE_LEVELS];
// count colors
if (opts.trans_mode == 0)
{
for (unsigned j = 0; j < TRANSPARENCY_LEVELS; ++j)
{
cols[j] = 0;
}
cols[TRANSPARENCY_LEVELS - 1] = width * height;
}
else
{
for (unsigned j = 0; j < TRANSPARENCY_LEVELS; ++j)
{
cols[j] = 0;
for (unsigned i = limits[j]; i < limits[j + 1]; ++i)
{
cols[j] += alphaHist[i];
}
}
}
unsigned divCoef = width * height - cols[0];
if (divCoef == 0)
{
divCoef = 1;
}
cols[0] = cols[0] > 0 ? 1 : 0; // fully transparent color (one or not at all)
if (opts.colors >= 64)
{
// give chance less populated but not empty cols to have at least few colors(12)
unsigned minCols = (12 + 1) * divCoef / (opts.colors - cols[0]);
for (unsigned j = 1; j < TRANSPARENCY_LEVELS; ++j)
{
if (cols[j] > 12 && cols[j] < minCols)
{
divCoef += minCols - cols[j];
cols[j] = minCols;
}
}
}
unsigned usedColors = cols[0];
for (unsigned j = 1; j < TRANSPARENCY_LEVELS - 1; ++j)
{
cols[j] = cols[j] * (opts.colors - cols[0]) / divCoef;
usedColors += cols[j];
}
// use rest for most opaque group of pixels
cols[TRANSPARENCY_LEVELS - 1] = opts.colors - usedColors;
// no transparency
if (opts.trans_mode == 0)
{
limits[1] = 0;
cols[0] = 0;
cols[1] = opts.colors;
}
// octree table for separate alpha range with 1-based index (0 is fully transparent: no color)
octree<rgb> trees[MAX_OCTREE_LEVELS];
for (unsigned j = 1; j < TRANSPARENCY_LEVELS; ++j)
{
trees[j].setMaxColors(cols[j]);
}
for (unsigned y = 0; y < height; ++y)
{
typename T2::pixel_type const* row = image.get_row(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
// insert to proper tree based on alpha range
for (unsigned j = TRANSPARENCY_LEVELS - 1; j > 0; --j)
{
if (cols[j] > 0 && U2ALPHA(val) >= limits[j])
{
trees[j].insert(mapnik::rgb(U2RED(val), U2GREEN(val), U2BLUE(val)));
break;
}
}
}
}
unsigned leftovers = 0;
std::vector<rgb> palette;
palette.reserve(opts.colors);
if (cols[0])
{
palette.push_back(rgb(0, 0, 0));
}
for (unsigned j = 1; j < TRANSPARENCY_LEVELS; ++j)
{
if (cols[j] > 0)
{
if (leftovers > 0)
{
cols[j] += leftovers;
trees[j].setMaxColors(cols[j]);
leftovers = 0;
}
std::vector<rgb> pal;
trees[j].setOffset(static_cast<unsigned>(palette.size()));
trees[j].create_palette(pal);
leftovers = cols[j] - static_cast<unsigned>(pal.size());
cols[j] = static_cast<unsigned>(pal.size());
palette.insert(palette.end(), pal.begin(), pal.end());
}
}
// transparency values per palette index
std::vector<unsigned> alpha_table;
// alpha_table.resize(palette.size());//allow semitransparency also in almost opaque range
if (opts.trans_mode != 0)
{
alpha_table.resize(palette.size() - cols[TRANSPARENCY_LEVELS - 1]);
}
if (palette.size() > 16)
{
// >16 && <=256 colors -> write 8-bit color depth
image_gray8 reduced_image(width, height);
reduce_8(image, reduced_image, trees, limits, TRANSPARENCY_LEVELS, alpha_table);
save_as_png(file, palette, reduced_image, width, height, 8, alpha_table, opts);
}
else if (palette.size() == 1)
{
// 1 color image -> write 1-bit color depth PNG
unsigned image_width = ((width + 15) >> 3) & ~1U; // 1-bit image, round up to 16-bit boundary
unsigned image_height = height;
image_gray8 reduced_image(image_width, image_height);
reduce_1(image, reduced_image, trees, limits, alpha_table);
if (meanAlpha < 255 && cols[0] == 0)
{
alpha_table.resize(1);
alpha_table[0] = meanAlpha;
}
save_as_png(file, palette, reduced_image, width, height, 1, alpha_table, opts);
}
else
{
// <=16 colors -> write 4-bit color depth PNG
unsigned image_width = ((width + 7) >> 1) & ~3U; // 4-bit image, round up to 32-bit boundary
unsigned image_height = height;
image_gray8 reduced_image(image_width, image_height);
reduce_4(image, reduced_image, trees, limits, TRANSPARENCY_LEVELS, alpha_table);
save_as_png(file, palette, reduced_image, width, height, 4, alpha_table, opts);
}
}
template<typename T1, typename T2, typename T3>
void save_as_png8(T1& file,
T2 const& image,
T3 const& tree,
std::vector<mapnik::rgb> const& palette,
std::vector<unsigned> const& alpha_table,
png_options const& opts)
{
unsigned width = image.width();
unsigned height = image.height();
if (palette.size() > 16)
{
// >16 && <=256 colors -> write 8-bit color depth
image_gray8 reduced_image(width, height);
for (unsigned y = 0; y < height; ++y)
{
mapnik::image_rgba8::pixel_type const* row = image.get_row(y);
mapnik::image_gray8::pixel_type* row_out = reduced_image.get_row(y);
for (unsigned x = 0; x < width; ++x)
{
row_out[x] = tree.quantize(row[x]);
}
}
save_as_png(file, palette, reduced_image, width, height, 8, alpha_table, opts);
}
else if (palette.size() == 1)
{
// 1 color image -> write 1-bit color depth PNG
unsigned image_width = ((width + 15) >> 3) & ~1U; // 1-bit image, round up to 16-bit boundary
unsigned image_height = height;
image_gray8 reduced_image(image_width, image_height);
reduced_image.set(0);
save_as_png(file, palette, reduced_image, width, height, 1, alpha_table, opts);
}
else
{
// <=16 colors -> write 4-bit color depth PNG
unsigned image_width = ((width + 7) >> 1) & ~3U; // 4-bit image, round up to 32-bit boundary
unsigned image_height = height;
image_gray8 reduced_image(image_width, image_height);
for (unsigned y = 0; y < height; ++y)
{
mapnik::image_rgba8::pixel_type const* row = image.get_row(y);
mapnik::image_gray8::pixel_type* row_out = reduced_image.get_row(y);
std::uint8_t index = 0;
for (unsigned x = 0; x < width; ++x)
{
index = tree.quantize(row[x]);
if (x % 2 == 0)
{
index = index << 4;
}
row_out[x >> 1] |= index;
}
}
save_as_png(file, palette, reduced_image, width, height, 4, alpha_table, opts);
}
}
template<typename T1, typename T2>
void save_as_png8_hex(T1& file, T2 const& image, png_options const& opts)
{
unsigned width = image.width();
unsigned height = image.height();
if (width + height > 3) // at least 3 pixels (hextree implementation requirement)
{
// structure for color quantization
hextree<mapnik::rgba> tree(opts.colors);
if (opts.trans_mode >= 0)
{
tree.setTransMode(opts.trans_mode);
}
if (opts.gamma > 0)
{
tree.setGamma(opts.gamma);
}
for (unsigned y = 0; y < height; ++y)
{
typename T2::pixel_type const* row = image.get_row(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
tree.insert(mapnik::rgba(U2RED(val), U2GREEN(val), U2BLUE(val), U2ALPHA(val)));
}
}
// transparency values per palette index
std::vector<mapnik::rgba> rgba_palette;
tree.create_palette(rgba_palette);
auto size = rgba_palette.size();
std::vector<mapnik::rgb> palette;
std::vector<unsigned> alpha_table;
palette.reserve(size);
alpha_table.reserve(size);
for (auto const& c : rgba_palette)
{
palette.emplace_back(c.r, c.g, c.b);
alpha_table.push_back(c.a);
}
save_as_png8<T1, T2, hextree<mapnik::rgba>>(file, image, tree, palette, alpha_table, opts);
}
else
{
std::set<mapnik::rgba> colors;
for (unsigned y = 0; y < height; ++y)
{
typename T2::pixel_type const* row = image.get_row(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
colors.emplace(U2RED(val), U2GREEN(val), U2BLUE(val), U2ALPHA(val));
}
}
std::string str;
for (auto c : colors)
{
str.push_back(c.r);
str.push_back(c.g);
str.push_back(c.b);
str.push_back(c.a);
}
rgba_palette pal(str, rgba_palette::PALETTE_RGBA);
save_as_png8<T1, T2, rgba_palette>(file, image, pal, pal.palette(), pal.alpha_table(), opts);
}
}
template<typename T1, typename T2>
void save_as_png8_pal(T1& file, T2 const& image, rgba_palette const& pal, png_options const& opts)
{
save_as_png8<T1, T2, rgba_palette>(file, image, pal, pal.palette(), pal.alpha_table(), opts);
}
} // namespace mapnik
#endif // MAPNIK_PNG_IO_HPP
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