img_median_3x3.h

dm642函数库

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/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  IMGLIB  DSP Image/Video Processing Library                              */
/*                                                                          */
/*      Release:        Revision 1.04b                                      */
/*      CVS Revision:   1.14    Thu Sep 11 18:42:51 2003 (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.                            */
/* ======================================================================== */
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/*  Assembler compatibility shim for assembling 4.30 and later code on      */
/*  tools prior to 4.30.                                                    */
/* ======================================================================== */
/* ======================================================================== */
/*  End of assembler compatibility shim.                                    */
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/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  NAME                                                                    */
/*      IMG_median_3x3                                                      */
/*                                                                          */
/*  REVISION DATE                                                           */
/*      11-Sep-2003                                                         */
/*                                                                          */
/*  USAGE                                                                   */
/*      This routine is C-callable and can be called as:                    */
/*                                                                          */
/*          void IMG_median_3x3                                             */
/*          (                                                               */
/*             const unsigned char *restrict i_data, // Input image     //  */
/*             int n,                    // Length of input (or output) //  */
/*             unsigned char       *restrict o_data  // Output image    //  */
/*          )                                                               */
/*                                                                          */
/*  DESCRIPTION                                                             */
/*      This kernel performs a 3x3 median filter operation on 8-bit         */
/*      unsigned values.  The median filter comes under the class           */
/*      of non-linear signal processing algorithms.                         */
/*                                                                          */
/*      Rather than replace the grey level at a pixel by a weighted         */
/*      average of the nine pixels including and surrounding it, the        */
/*      grey level at each pixel is replaced by the median of the nine      */
/*      values.  The median of a set of nine numbers is the middle          */
/*      element so that half of the elements in the list are larger and     */
/*      half are smaller.  Median filters remove the effects of extreme     */
/*      values from data, such as salt and pepper noise, although using     */
/*      a wide may result in unacceptable blurring of sharp edges in        */
/*      the original image.                                                 */
/*                                                                          */
/*  C CODE                                                                  */
/*      The following is a C code description of the algorithm without      */
/*      restrictions.  The optimized implementations may have               */
/*      restrictions, as noted under the "ASSUMPTIONS" below.               */
/*                                                                          */
/*      void IMG_median_3x3                                                 */
/*      (                                                                   */
/*          const unsigned char *restrict i_data,                           */
/*          int n,                                                          */
/*          unsigned char       *restrict o_data                            */
/*      )                                                                   */
/*      {                                                                   */
/*          unsigned char c0h, c1h, c2h; // "hi",  columns 0..2 //          */
/*          unsigned char c0m, c1m, c2m; // "mid", columns 0..2 //          */
/*          unsigned char c0l, c1l, c2l; // "lo",  columns 0..2 //          */
/*          unsigned char h_min;         // "min" //                        */
/*          unsigned char m_mid;         // "mid" //                        */
/*          unsigned char l_max;         // "max" //                        */
/*          unsigned char m_h, m_l, t, out;                                 */
/*                                                                          */
/*          int i;                                                          */
/*                                                                          */
/*          // ---------------------------------------------------- //      */
/*          //  Start off with a well-defined initial state.        //      */
/*          // ---------------------------------------------------- //      */
/*          c1h = c2h = c1m = c2m = c1l = c2l = 127;                        */
/*                                                                          */
/*          // ---------------------------------------------------- //      */
/*          //  Iterate over the input row.                         //      */
/*          // ---------------------------------------------------- //      */
/*          for (i = 0; i < n; i++)                                         */
/*          {                                                               */
/*              // ------------------------------------------------ //      */
/*              //  Slide the two previous columns of sorted        //      */
/*              //  pixels over by 1.                               //      */
/*              // ------------------------------------------------ //      */
/*              c0h = c1h;    c1h = c2h;                                    */
/*              c0m = c1m;    c1m = c2m;                                    */
/*              c0l = c1l;    c1l = c2l;                                    */
/*                                                                          */
/*              // ------------------------------------------------ //      */
/*              //  Load in a new column of pixels, and sort into   //      */
/*              //  low, medium, high.                              //      */
/*              // ------------------------------------------------ //      */
/*              c2h = i_data[i      ];                                      */
/*              c2m = i_data[i +   n];                                      */
/*              c2l = i_data[i + 2*n];                                      */
/*                                                                          */
/*              if (c2l > c2h) { t = c2l; c2l = c2h; c2h = t; }             */
/*              if (c2l > c2m) { t = c2l; c2l = c2m; c2m = t; }             */
/*              if (c2m > c2h) { t = c2m; c2m = c2h; c2h = t; }             */
/*                                                                          */
/*              // ------------------------------------------------ //      */