File content as of revision 5:c4c66c630011:

//------------------------------------------------------------------------------
// picojpeg v1.0 - Public domain, Rich Geldreich <richgel99@gmail.com>
//------------------------------------------------------------------------------
#ifndef PICOJPEG_H
#define PICOJPEG_H

#ifdef __cplusplus
extern "C" {
#endif

// Error codes
enum
{
   PJPG_NO_MORE_BLOCKS = 1,
   PJPG_BAD_DHT_COUNTS,
   PJPG_BAD_DHT_INDEX,
   PJPG_BAD_DHT_MARKER,
   PJPG_BAD_DQT_MARKER,
   PJPG_BAD_DQT_TABLE,
   PJPG_BAD_PRECISION,
   PJPG_BAD_HEIGHT,
   PJPG_BAD_WIDTH,
   PJPG_TOO_MANY_COMPONENTS,
   PJPG_BAD_SOF_LENGTH,
   PJPG_BAD_VARIABLE_MARKER,
   PJPG_BAD_DRI_LENGTH,
   PJPG_BAD_SOS_LENGTH,
   PJPG_BAD_SOS_COMP_ID,
   PJPG_W_EXTRA_BYTES_BEFORE_MARKER,
   PJPG_NO_ARITHMITIC_SUPPORT,
   PJPG_UNEXPECTED_MARKER,
   PJPG_NOT_JPEG,
   PJPG_UNSUPPORTED_MARKER,
   PJPG_BAD_DQT_LENGTH,
   PJPG_TOO_MANY_BLOCKS,
   PJPG_UNDEFINED_QUANT_TABLE,
   PJPG_UNDEFINED_HUFF_TABLE,
   PJPG_NOT_SINGLE_SCAN,
   PJPG_UNSUPPORTED_COLORSPACE,
   PJPG_UNSUPPORTED_SAMP_FACTORS,
   PJPG_DECODE_ERROR,
   PJPG_BAD_RESTART_MARKER,
   PJPG_ASSERTION_ERROR,
   PJPG_BAD_SOS_SPECTRAL,
   PJPG_BAD_SOS_SUCCESSIVE,
   PJPG_STREAM_READ_ERROR,
   PJPG_NOTENOUGHMEM,
   PJPG_UNSUPPORTED_COMP_IDENT,
   PJPG_UNSUPPORTED_QUANT_TABLE,
   PJPG_UNSUPPORTED_MODE,
};  

// Scan types - currently only GRAYSCALE, YH1V1, and YH2V2 are actually supported.
typedef enum
{
   PJPG_GRAYSCALE,
   PJPG_YH1V1,
   PJPG_YH2V1,
   PJPG_YH1V2,
   PJPG_YH2V2
} pjpeg_scan_type_t;

typedef struct
{
   // Image resolution
   int m_width;
   int m_height;
   // Number of components (1 or 3)
   int m_comps;
   // Total number of minimum coded units (MCU's) per row/col.
   int m_MCUSPerRow;
   int m_MCUSPerCol;
   // Scan type
   pjpeg_scan_type_t m_scanType;
   // MCU width/height in pixels
   int m_MCUWidth;
   int m_MCUHeight;
   // Pointers to internal MCU pixel component buffers. 
   // These buffers Will be filled with pixels each time pjpegDecodeMCU() is called successfully.
   // Each MCU consists of (m_MCUWidth/8)*(m_MCUHeight/8) blocks (currently either 1 for greyscale/no subsampling, or 4 for H2V2 sampling factors), where each block is a contiguous array of 64 (8x8) bytes.
   // For greyscale images, only the values in m_pMCUBufR are valid.
   unsigned char *m_pMCUBufR;
   unsigned char *m_pMCUBufG;
   unsigned char *m_pMCUBufB;
} pjpeg_image_info_t;

typedef unsigned char (*pjpeg_need_bytes_callback_t)(unsigned char* pBuf, unsigned char buf_size, unsigned char *pBytes_actually_read, void *pCallback_data);

// Initializes the decompressor. Returns 0 on success, or one of the above error codes on failure.
// pNeed_bytes_callback will be called to fill the decompressor's internal input buffer.
// Not thread safe.
unsigned char pjpeg_decode_init(pjpeg_image_info_t *pInfo, pjpeg_need_bytes_callback_t pNeed_bytes_callback, void *pCallback_data);

// Decompresses the file's next MCU. Returns 0 on success, PJPG_NO_MORE_BLOCKS if no more blocks are available, or an error code.
// Must be called a total of m_MCUSPerRow*m_MCUSPerCol times to completely decompress the image.
unsigned char pjpeg_decode_mcu(void);

#ifdef __cplusplus
}
#endif

#endif // PICOJPEG_H