File picojpeg.h

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//------------------------------------------------------------------------------
// picojpeg - 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, // picojpeg doesn't support progressive JPEG's
};

// Scan types
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 (each is either 8 or 16 depending on the scan
    // type)
    int m_MCUWidth;
    int m_MCUHeight;

    // m_pMCUBufR, m_pMCUBufG, and m_pMCUBufB are pointers to internal MCU Y or
    // RGB pixel component buffers. Each time pjpegDecodeMCU() is called
    // successfully these buffers will be filled with 8x8 pixel blocks of Y or RGB
    // pixels. Each MCU consists of (m_MCUWidth/8)*(m_MCUHeight/8) Y/RGB blocks: 1
    // for greyscale/no subsampling, 2 for H1V2/H2V1, or 4 blocks for H2V2
    // sampling factors. Each block is a contiguous array of 64 (8x8) bytes of a
    // single component: either Y for grayscale images, or R, G or B components
    // for color images.
    //
    // The 8x8 pixel blocks are organized in these byte arrays like this:
    //
    // PJPG_GRAYSCALE: Each MCU is decoded to a single block of 8x8 grayscale
    // pixels. Only the values in m_pMCUBufR are valid. Each 8 bytes is a row of
    // pixels (raster order: left to right, top to bottom) from the 8x8 block.
    //
    // PJPG_H1V1: Each MCU contains is decoded to a single block of 8x8 RGB
    // pixels.
    //
    // PJPG_YH2V1: Each MCU is decoded to 2 blocks, or 16x8 pixels.
    // The 2 RGB blocks are at byte offsets: 0, 64
    //
    // PJPG_YH1V2: Each MCU is decoded to 2 blocks, or 8x16 pixels.
    // The 2 RGB blocks are at byte offsets: 0,
    //                                       128
    //
    // PJPG_YH2V2: Each MCU is decoded to 4 blocks, or 16x16 pixels.
    // The 2x2 block array is organized at byte offsets:   0,  64,
    //                                                   128, 192
    //
    // It is up to the caller to copy or blit these pixels from these buffers into
    // the destination bitmap.
    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. If reduce is 1, only the first pixel of
// each block will be decoded. This mode is much faster because it skips the AC
// dequantization, IDCT and chroma upsampling of every image pixel. Not thread
// safe.
unsigned char pjpeg_decode_init(
    pjpeg_image_info_t *pInfo, pjpeg_need_bytes_callback_t pNeed_bytes_callback,
    void *pCallback_data, unsigned char reduce);

// 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. Not
// thread safe.
unsigned char pjpeg_decode_mcu(void);

#ifdef __cplusplus
}
#endif

#endif // PICOJPEG_H