img_thr_gt2thr.h

dm642函数库

/* ======================================================================== */
/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  IMGLIB  DSP Image/Video Processing Library                              */
/*                                                                          */
/*      Release:        Revision 1.04b                                      */
/*      CVS Revision:   1.5     Sun Sep 29 03:32:30 2002 (UTC)              */
/*      Snapshot date:  23-Oct-2003                                         */
/*                                                                          */
/*  This library contains proprietary intellectual property of Texas        */
/*  Instruments, Inc.  The library and its source code are protected by     */
/*  various copyrights, and portions may also be protected by patents or    */
/*  other legal protections.                                                */
/*                                                                          */
/*  This software is licensed for use with Texas Instruments TMS320         */
/*  family DSPs.  This license was provided to you prior to installing      */
/*  the software.  You may review this license by consulting the file       */
/*  TI_license.PDF which accompanies the files in this library.             */
/* ------------------------------------------------------------------------ */
/*          Copyright (C) 2003 Texas Instruments, Incorporated.             */
/*                          All Rights Reserved.                            */
/* ======================================================================== */
/* ======================================================================== */
/*  Assembler compatibility shim for assembling 4.30 and later code on      */
/*  tools prior to 4.30.                                                    */
/* ======================================================================== */
/* ======================================================================== */
/*  End of assembler compatibility shim.                                    */
/* ======================================================================== */
/* ======================================================================== */
/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  NAME                                                                    */
/*      IMG_thr_gt2thr                                                      */
/*                                                                          */
/*                                                                          */
/*  REVISION DATE                                                           */
/*      13-Sep-2002                                                         */
/*                                                                          */
/*  USAGE                                                                   */
/*      This routine has the following C prototype:                         */
/*                                                                          */
/*      void IMG_thr_gt2thr                                                 */
/*      (                                                                   */
/*          const unsigned char *in_data,     //  Input image data  //      */
/*          unsigned char *restrict out_data, //  Output image data //      */
/*          short cols, short rows,           //  Image dimensions  //      */
/*          unsigned char       threshold     //  Threshold value   //      */
/*      )                                                                   */
/*                                                                          */
/*      This routine performs a thresholding operation on an input          */
/*      image in in_data[] whose dimensions are given in the arguments      */
/*      'cols' and 'rows'.  The thresholded pixels are written to the       */
/*      output image pointed to by out_data[].  The input and output        */
/*      are exactly the same dimensions.                                    */
/*                                                                          */
/*  DESCRIPTION                                                             */
/*      Pixels that are above the threshold value are written to the        */
/*      output unmodified.  Pixels that are greater than the threshold      */
/*      are set to the threshold value in the output image.                 */
/*                                                                          */
/*      The exact thresholding function performed is described by           */
/*      the following transfer function diagram:                            */
/*                                                                          */
/*                                                                          */
/*                 255_|                                                    */
/*                     |                                                    */
/*                     |                                                    */
/*            O        |                                                    */
/*            U        |                                                    */
/*            T    th _|. . . . . _________                                 */
/*            P        |        /.                                          */
/*            U        |      /  .                                          */
/*            T        |    /    .                                          */
/*                     |  /      .                                          */
/*                   0_|/________.__________                                */
/*                     |         |        |                                 */
/*                     0        th       255                                */
/*                                                                          */
/*                             INPUT                                        */
/*                                                                          */
/*      Please see the IMGLIB functions IMG_thr_le2thr, IMG_thr_gt2max      */
/*      and IMG_thr_le2min for other thresholding functions.                */
/*                                                                          */
/*  ASSUMPTIONS                                                             */
/*      The input and output buffers do not alias.                          */
/*                                                                          */
/*      The input and output buffers must be double-word aligned.           */
/*                                                                          */
/*      The total number of pixels rows*cols must be at least               */
/*      16 and a multiple of 16.                                            */
/*                                                                          */
/*  TECHNIQUES                                                              */
/*      The loop is unrolled 16x.  Packed-data processing techniques        */
/*      allow us to process all 16 pixels in parallel.                      */
/*                                                                          */
/*      Two LDDW instructions load in 16 pixels, designated p0 thru p9      */
/*      pA thru pF.  These pixels are packed in the four registers pFEDC,   */
/*      pBA98, p7654, and p3210 as follows:                                 */
/*                                                                          */
/*          Upper double-word:                                              */
/*                                                                          */
/*               31  24   16    8    0          31  24   16    8    0       */
/*                +----+----+----+----+          +----+----+----+----+      */
/*          pFEDC | pF | pE | pD | pC |    pBA98 | pB | pA | p9 | p8 |      */
/*                +----+----+----+----+          +----+----+----+----+      */
/*                                                                          */
/*          Lower double-word:                                              */
/*                                                                          */
/*               31  24   16    8    0          31  24   16    8    0       */
/*                +----+----+----+----+          +----+----+----+----+      */
/*          p7654 | p7 | p6 | p5 | p4 |    p3210 | p3 | p2 | p1 | p0 |      */
/*                +----+----+----+----+          +----+----+----+----+      */
/*                                                                          */
/*      (Note that this diagram assumes a little endian memory              */
/*      configuration, although this kernel works equally well in           */
/*      either endian mode.)                                                */
/*                                                                          */
/*      We compare these four words against a packed copy of the threshold  */
/*      value.  The packed threshold contains four copies of the threshold  */
/*      value, one in each byte, like so:                                   */
/*                                                                          */
/*                             31  24   16    8    0                        */
/*                              +----+----+----+----+                       */
/*                     thththth | th | th | th | th |                       */
/*                              +----+----+----+----+                       */
/*                                                                          */
/*      We compare using MINU4.  This instruction with select the smaller   */
/*      value between our input pixels and the threshold value.  The        */
/*      result is that input values above the threshold are clamped to the  */
/*      threshold value.                                                    */
/*                                                                          */
/*      The 16 results are then written with two STDWs.                     */
/*                                                                          */
/*  MEMORY NOTE                                                             */
/*      This code is ENDIAN NEUTRAL.                                        */
/*                                                                          */
/*      The input and output arrays must be double-word aligned.            */
/*                                                                          */
/*      No bank conflicts occur, regardless of the relative alignment of    */
/*      in_data[] and out_data[].                                           */
/*                                                                          */
/*  CYCLES                                                                  */
/*      cycles = 0.125 * rows * cols + 20.                                  */
/*      For rows = 32 and cols = 32, cycles = 148.                          */
/*                                                                          */
/*      This number includes 6 cycles of function call overhead.  The       */
/*      exact overhead will vary depending on compiler options used.        */
/*                                                                          */
/*  CODESIZE                                                                */
/*      108 bytes.                                                          */
/* ------------------------------------------------------------------------ */
/*            Copyright (c) 2003 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================== */
#ifndef IMG_THR_GT2THR_H_
#define IMG_THR_GT2THR_H_ 1

void IMG_thr_gt2thr
(
    const unsigned char *in_data,     /*  Input image data  */
    unsigned char *restrict out_data, /*  Output image data */
    short cols, short rows,           /*  Image dimensions  */
    unsigned char       threshold     /*  Threshold value   */
);

#endif
/* ======================================================================== */
/*  End of file:  img_thr_gt2thr.h                                          */
/* ------------------------------------------------------------------------ */
/*            Copyright (c) 2003 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================== */