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#ifndef PNGREAD_HPP
#define PNGREAD_HPP
#include <vector>
#include <string>
#include <istream>
namespace Slic3r { namespace png {
// Interface for an input stream of encoded png image data.
struct IStream {
virtual ~IStream() = default;
virtual size_t read(std::uint8_t *outp, size_t amount) = 0;
virtual bool is_ok() const = 0;
};
// The output format of decode_png: a 2D pixel matrix stored continuously row
// after row (row major layout).
template<class PxT> struct Image {
std::vector<PxT> buf;
size_t rows, cols;
PxT get(size_t row, size_t col) const { return buf[row * cols + col]; }
};
using ImageGreyscale = Image<uint8_t>;
// Only decodes true 8 bit grayscale png images. Returns false for other formats
// TODO (if needed): implement transformation of rgb images into grayscale...
bool decode_png(IStream &stream, ImageGreyscale &out_img);
// TODO (if needed)
// struct RGB { uint8_t r, g, b; };
// using ImageRGB = Image<RGB>;
// bool decode_png(IStream &stream, ImageRGB &img);
// Encoded png data buffer: a simple read-only buffer and its size.
struct ReadBuf { const void *buf = nullptr; const size_t sz = 0; };
bool is_png(const ReadBuf &pngbuf);
template<class Img> bool decode_png(const ReadBuf &in_buf, Img &out_img)
{
struct ReadBufStream: public IStream {
const ReadBuf &rbuf_ref; size_t pos = 0;
explicit ReadBufStream(const ReadBuf &buf): rbuf_ref{buf} {}
size_t read(std::uint8_t *outp, size_t amount) override
{
if (amount > rbuf_ref.sz - pos) return 0;
auto buf = static_cast<const std::uint8_t *>(rbuf_ref.buf);
std::copy(buf + pos, buf + (pos + amount), outp);
pos += amount;
return amount;
}
bool is_ok() const override { return pos < rbuf_ref.sz; }
} stream{in_buf};
return decode_png(stream, out_img);
}
// TODO: std::istream of FILE* could be similarly adapted in case its needed...
}} // namespace Slic3r::png
#endif // PNGREAD_HPP
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