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Add a simple PNG image encoder with Lua API (#11485)

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* Add a simple PNG image encoder with Lua API
Add ColorSpec to RGBA converter
Make a safety wrapper for the encoder
Create devtest examples

Co-authored-by: hecktest <>
Co-authored-by: sfan5 <sfan5@live.de>
This commit is contained in:
hecks 2021-07-29 05:10:10 +02:00 • committed by GitHub
parent 2866918f32
commit 80d12dbedb
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9 changed files with 278 additions and 1 deletions
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src/util/png.cpp Executable file
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/*
Minetest
Copyright (C) 2021 hecks
This program 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 program 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 program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "png.h"
#include <string>
#include <sstream>
#include <zlib.h>
#include <cassert>
#include "util/serialize.h"
#include "serialization.h"
#include "irrlichttypes.h"
static void writeChunk(std::ostringstream &target, const std::string &chunk_str)
{
assert(chunk_str.size() >= 4);
assert(chunk_str.size() - 4 < U32_MAX);
writeU32(target, chunk_str.size() - 4); // Write length minus the identifier
target << chunk_str;
writeU32(target, crc32(0,(const u8*)chunk_str.data(), chunk_str.size()));
}
std::string encodePNG(const u8 *data, u32 width, u32 height, s32 compression)
{
auto file = std::ostringstream(std::ios::binary);
file << "\x89PNG\r\n\x1a\n";
{
auto IHDR = std::ostringstream(std::ios::binary);
IHDR << "IHDR";
writeU32(IHDR, width);
writeU32(IHDR, height);
// 8 bpp, color type 6 (RGBA)
IHDR.write("\x08\x06\x00\x00\x00", 5);
writeChunk(file, IHDR.str());
}
{
auto IDAT = std::ostringstream(std::ios::binary);
IDAT << "IDAT";
auto scanlines = std::ostringstream(std::ios::binary);
for(u32 i = 0; i < height; i++) {
scanlines.write("\x00", 1); // Null predictor
scanlines.write((const char*) data + width * 4 * i, width * 4);
}
compressZlib(scanlines.str(), IDAT, compression);
writeChunk(file, IDAT.str());
}
file.write("\x00\x00\x00\x00IEND\xae\x42\x60\x82", 12);
return file.str();
}