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