JpegDecoder.h

#pragma once

#include <cstdlib>
#include <cstdio>
#include <cstdint>

#include <jpeglib.h>

namespace DStream
{
	class JpegDecoder
	{
	public:
		JpegDecoder();
		~JpegDecoder();

		JpegDecoder(const JpegDecoder&) = delete;
		void operator=(const JpegDecoder&) = delete;

		//JCS_GRAYSCALE, JCS_RGB, JCS_YCbCr, or JCS_CMYK.

		void setColorSpace(J_COLOR_SPACE space);
		void setJpegColorSpace(J_COLOR_SPACE colorSpace);
		J_COLOR_SPACE getColorSpace() const;
		bool decode(uint8_t* buffer, size_t len, uint8_t*& img, int& width, int& height);
		bool decode(const char* path, uint8_t*& img, int& width, int& height);
		bool decodeNonAlloc(const char* path, uint8_t* buffer, int& width, int& height);
		bool decode(FILE* file, uint8_t*& img, int& width, int& height);

		//file streaming reading support
		bool init(const char* path, int& width, int& height);

		size_t rowSize() { return decInfo.image_width * decInfo.num_components; }

		//buffer must have rows*rowSize() space at least!
		size_t readRows(int rows, uint8_t* buffer); //return false on end.
		bool finish();
		bool restart();
		bool chromaSubsampled() { return subsampled; }

	private:
		FILE* file = nullptr;
		bool init(int& width, int& height);
		bool decode(uint8_t*& img, int& width, int& height);

		jpeg_decompress_struct decInfo;
		jpeg_error_mgr errMgr;

		J_COLOR_SPACE colorSpace = JCS_RGB;
		J_COLOR_SPACE jpegColorSpace = JCS_YCbCr;

		bool subsampled = false;
	};
}