bmpi_16bit_decoder.c

bmp图像文件解码器的arm版本的源代码

/*

*******************************************************************************
*
* FILE NAME:            
*   bmp_16bit_decoder.c
*
* DESCRIPTION:
*   source code for BMP decoder with 16-bit.
*
* MODULE: 
*   BMP (BitMaP) decoder.
* 

*  
*******************************************************************************
*/

/*
*******************************************************************************
* Include files
*******************************************************************************
*/

/* -- Include for BMP ressources -- */
#include "bmp_decoder_api.h"
#include "bmpi_decoder.h"



/*
*******************************************************************************
* 
* FUNCTION NAME:
*   BMPI_Decode16Bits()
*
* FUNCTION DESCRIPTION:
*   This function decodes a BMP image with 16-bit color.
*
* INPUTS:
*   pu8InputBuffer  : pointer to input buffer
*   pu8Mask         : pointer to color mask in palette
*   sImageInfo      : image information structure 
*   func            : pointer to callback function
*
* OUTPUTS:
*   psOutputBuffer  : pointer to output buffer (structure)
*   
* RETURN:
*   '0' if successful or '1' if failed.
*
* GLOBALS ACCESSED/MODIFIED:
*   < List all global variables this function accesses and/or modifies >
*
* SPECIAL NOTES:
*
*******************************************************************************
*/
OP_UINT8 BMPI_Decode16Bits
(
    OP_UINT8                    *pu8InputBuffer,
    OP_UINT8                    *pu8Mask,
    BMP_IMAGE_INFO              sImageInfo,
    OP_BOOLEAN                  func(OP_UINT16 x, OP_UINT16 y),
    IMAGE_DECODER_OUTPUT_TYPE   *psOutputBuffer
)
{
    /*-----------------------------------------------------------------------*/
    /* DECLARE LOCAL VARIABLES                                                 */
    /*-----------------------------------------------------------------------*/

    OP_UINT16   u16RedMask;             /* mask for red color */
    OP_UINT16   u16GreenMask;           /* mask for green color */
    OP_UINT16   u16BlueMask;            /* mask for blue color */
    OP_UINT16   u16RedShift;            /* shift value used in decoding red color */
    OP_UINT16   u16GreenShift;          /* shift value used in decoding green color */
    OP_UINT16   u16BlueShift;           /* shift value used in decoding blue color */
    OP_UINT16   u16RedScaling;          /* scaling value used in decoding red color */
    OP_UINT16   u16GreenScaling;        /* scaling value used in decoding green color */
    OP_UINT16   u16BlueScaling;         /* scaling value used in decoding blue color */
    OP_UINT16   u16Temp;                /* 16-bit temporary variable */
    OP_UINT32   u32NumExtraByte;        /* number of extra bytes in a line */
    OP_UINT32   u32XinvCnt;             /* inverse counter on X-axis */
    OP_UINT32   u32YinvCnt;             /* inverse counter on Y-axis */
    OP_UINT32   u32Temp;                /* 32-bit temporary variable */


    /*-----------------------------------------------------------------------*/
    /* DECODE 16-BIT COLORS                                                   */
    /*-----------------------------------------------------------------------*/

    /* determine bit masks for each color plane */
    if(sImageInfo.u32Compression == BI_RGB) /* with conventional bit masking */
    {
        u16RedMask      = 0x7c00;
        u16GreenMask    = 0x03e0;
        u16BlueMask     = 0x001f;
        u16RedShift     = 10;
        u16GreenShift   = 5;
        u16BlueShift    = 0;
        u16RedScaling   = 8;
        u16GreenScaling = 8;
        u16BlueScaling  = 8;
    }
    else                                        /* with specific bit masking */
    {
        u16RedMask   = (OP_UINT16)BMPI_ReadLittleEndianU32(pu8Mask);
        pu8Mask+=4;
        u16GreenMask = (OP_UINT16)BMPI_ReadLittleEndianU32(pu8Mask);
        pu8Mask+=4;
        u16BlueMask  = (OP_UINT16)BMPI_ReadLittleEndianU32(pu8Mask);
        BMPI_DetermineShiftScaling(u16RedMask, 
                                   &u16RedShift, 
                                   &u16RedScaling);
        BMPI_DetermineShiftScaling(u16GreenMask, 
                                   &u16GreenShift, 
                                   &u16GreenScaling);
        BMPI_DetermineShiftScaling(u16BlueMask, 
                                   &u16BlueShift, 
                                   &u16BlueScaling);
    }

    /* -- Calculate number of extra bytes in a line -- */
    u32Temp = (sImageInfo.u32ImageWidth*2) & 0x00000003;
    if ( u32Temp != 0 ) 
    {
        u32NumExtraByte = 4-u32Temp;
    }
    else
    {
        u32NumExtraByte = 0;
    }

    /* -- Extract 16-bit data in bitmap -- */
    /* vertical loop */
    u32YinvCnt = sImageInfo.u32ImageHeight;
    while(u32YinvCnt--)
    {

        /* horizontal loop */
        u32XinvCnt = sImageInfo.u32ImageWidth;
        while(u32XinvCnt--)                         /* releavant 16-bit data */
        {
            u16Temp = BMPI_ReadLittleEndianU16(pu8InputBuffer);
            pu8InputBuffer+=2;                   /* move to next 16-bit data */
            psOutputBuffer->u8Blue  = (OP_UINT8)((u16Temp & u16BlueMask) 
                >> u16BlueShift)*u16BlueScaling;
            psOutputBuffer->u8Green = (OP_UINT8)((u16Temp & u16GreenMask) 
                >> u16GreenShift)*u16GreenScaling;
            psOutputBuffer->u8Red   = (OP_UINT8)((u16Temp & u16RedMask) 
                >> u16RedShift)*u16RedScaling;
            psOutputBuffer->u8Alpha = 0xff;      /* set to opaque as default */
            psOutputBuffer++;                          /* move to next pixel */
        }
        pu8InputBuffer+=u32NumExtraByte;          /* dummy bytes are ignored */

    }


    /*-----------------------------------------------------------------------*/
    /* DECODED SUCCESSFULLY                                                  */
    /*-----------------------------------------------------------------------*/

    return(0);
}

 

/*
*******************************************************************************
* 
* FUNCTION NAME:
*   BMPI_DetermineShiftScaling()
*
* FUNCTION DESCRIPTION:
*   This function determines the shifting and scaling values used in 
*   calculating the color intensity. The shifting and scaling values
*   are derived from the input bit mask.
*
* INPUTS:
*   u16Mask  : input bit mask. 
*
* OUTPUTS:
*   u16Shift   : shift value derived from the input bit mask
*   u16Scaling : scaling value derived from input bit mask
*   
* RETURN:
*   None.
*
* GLOBALS ACCESSED/MODIFIED:
*   < List all global variables this function accesses and/or modifies >
*
* SPECIAL NOTES:
*
*******************************************************************************
*/
void BMPI_DetermineShiftScaling
(
    OP_UINT16       u16Mask, 
    OP_UINT16       *u16Shift, 
    OP_UINT16       *u16Scaling
)
{
    /*-----------------------------------------------------------------------*/
    /* DECLARE LOCAL VARIABLES                                                 */
    /*-----------------------------------------------------------------------*/

    OP_UINT16   u16Temp;                      /* 16-bit temporary variable */
 

    /*-----------------------------------------------------------------------*/
    /* INITIALIZE RETURNED PARAMETERS                                          */
    /*-----------------------------------------------------------------------*/

    *u16Shift = 0;
    *u16Scaling = 0x0080;


    /*-----------------------------------------------------------------------*/
    /* DETERMINE SHIFTING VALUE                                                 */
    /*-----------------------------------------------------------------------*/

    u16Temp = u16Mask & 0x0001;
    while( (!u16Temp) && (*u16Shift<16) )
    {
        u16Mask = (u16Mask >> 1) & 0x7fff;
        u16Temp = u16Mask & 0x0001;
        (*u16Shift)++;
    }


    /*-----------------------------------------------------------------------*/
    /* DETERMINE SCALING VALUE                                                 */
    /*-----------------------------------------------------------------------*/

    if(*u16Shift == 16)
    {
        *u16Scaling = 0;
    }
    else
    {
        u16Mask = u16Mask >> 1;
        while(u16Mask)
        {
            *u16Scaling = *u16Scaling >> 1; 
            u16Mask = u16Mask >> 1;
        }
    }

}