PrusaSlicer-NonPlainar/src/libslic3r/PNGRead.cpp
2020-08-27 23:14:42 +02:00

101 lines
3.0 KiB
C++

#include "PNGRead.hpp"
#include <memory>
#include <cstdio>
#include <png.h>
namespace Slic3r { namespace png {
struct PNGDescr {
png_struct *png = nullptr; png_info *info = nullptr;
PNGDescr() = default;
PNGDescr(const PNGDescr&) = delete;
PNGDescr(PNGDescr&&) = delete;
PNGDescr& operator=(const PNGDescr&) = delete;
PNGDescr& operator=(PNGDescr&&) = delete;
~PNGDescr()
{
if (png && info) png_destroy_info_struct(png, &info);
if (png) png_destroy_read_struct( &png, nullptr, nullptr);
}
};
bool is_png(const ReadBuf &rb)
{
static const constexpr int PNG_SIG_BYTES = 8;
#if PNG_LIBPNG_VER_MINOR <= 2
// Earlier libpng versions had png_sig_cmp(png_bytep, ...) which is not
// a const pointer. It is not possible to cast away the const qualifier from
// the input buffer so... yes... life is challenging...
png_byte buf[PNG_SIG_BYTES];
auto inbuf = static_cast<const std::uint8_t *>(rb.buf);
std::copy(inbuf, inbuf + PNG_SIG_BYTES, buf);
#else
auto buf = static_cast<png_const_bytep>(rb.buf);
#endif
return rb.sz >= PNG_SIG_BYTES && !png_sig_cmp(buf, 0, PNG_SIG_BYTES);
}
// Buffer read callback for libpng. It provides an allocated output buffer and
// the amount of data it desires to read from the input.
void png_read_callback(png_struct *png_ptr,
png_bytep outBytes,
png_size_t byteCountToRead)
{
// Retrieve our input buffer through the png_ptr
auto reader = static_cast<IStream *>(png_get_io_ptr(png_ptr));
if (!reader || !reader->is_ok()) return;
reader->read(static_cast<std::uint8_t *>(outBytes), byteCountToRead);
}
bool decode_png(IStream &in_buf, ImageGreyscale &out_img)
{
static const constexpr int PNG_SIG_BYTES = 8;
std::vector<png_byte> sig(PNG_SIG_BYTES, 0);
in_buf.read(sig.data(), PNG_SIG_BYTES);
if (!png_check_sig(sig.data(), PNG_SIG_BYTES))
return false;
PNGDescr dsc;
dsc.png = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, nullptr,
nullptr);
if(!dsc.png) return false;
dsc.info = png_create_info_struct(dsc.png);
if(!dsc.info) return false;
png_set_read_fn(dsc.png, static_cast<void *>(&in_buf), png_read_callback);
// Tell that we have already read the first bytes to check the signature
png_set_sig_bytes(dsc.png, PNG_SIG_BYTES);
png_read_info(dsc.png, dsc.info);
out_img.cols = png_get_image_width(dsc.png, dsc.info);
out_img.rows = png_get_image_height(dsc.png, dsc.info);
size_t color_type = png_get_color_type(dsc.png, dsc.info);
size_t bit_depth = png_get_bit_depth(dsc.png, dsc.info);
if (color_type != PNG_COLOR_TYPE_GRAY || bit_depth != 8)
return false;
out_img.buf.resize(out_img.rows * out_img.cols);
auto readbuf = static_cast<png_bytep>(out_img.buf.data());
for (size_t r = 0; r < out_img.rows; ++r)
png_read_row(dsc.png, readbuf + r * out_img.cols, nullptr);
return true;
}
}} // namespace Slic3r::png