img_sobel.h64

dm642函数库

;* ======================================================================== *;
;*  TEXAS INSTRUMENTS, INC.                                                 *;
;*                                                                          *;
;*  IMGLIB  DSP Image/Video Processing Library                              *;
;*                                                                          *;
;*      Release:        Revision 1.04b                                      *;
;*      CVS Revision:   1.6     Fri Oct 10 16:01:13 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.                            *;
;* ======================================================================== *;
;* ======================================================================== *;
;*  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_sobel, Little Endian.                                           *
*                                                                           *
*   REVISION DATE                                                           *
*       10-Oct-2003                                                         *
*                                                                           *
*   USAGE                                                                   *
*       This routine is C-callable and can be called as:                    *
*                                                                           *
*       void IMG_sobel                                                      *
*       (                                                                   *
*           const unsigned char *in_data,      /* Input image data  */      *
*           unsigned char       *out_data,     /* Output image data */      *
*           short cols, short rows             /* Image dimensions  */      *
*       )                                                                   *
*                                                                           *
*       The IMG_sobel filter is applied to the input image. The input image *
*       dimensions are given by the arguments 'cols' and 'rows'.  The       *
*       output image is 'cols' pixels wide and 'rows - 2' pixels tall.      *
*                                                                           *
*   DESCRIPTION                                                             *
*                                                                           *
*       To see how the implementation is going to work on the input         *
*       buffer, lets imagine we have the following input buffer:            *
*                                                                           *
*               yyyyyyyyyyyyyyyy                                            *
*               yxxxxxxxxxxxxxxy                                            *
*               yxxxxxxxxxxxxxxy                                            *
*               yxxxxxxxxxxxxxxy                                            *
*               yxxxxxxxxxxxxxxy                                            *
*               yyyyyyyyyyyyyyyy                                            *
*                                                                           *
*       The output buffer would be:                                         *
*                                                                           *
*               tXXXXXXXXXXXXXXz                                            *
*               zXXXXXXXXXXXXXXz                                            *
*               zXXXXXXXXXXXXXXz                                            *
*               zXXXXXXXXXXXXXXt                                            *
*                                                                           *
*       Where:                                                              *
*                                                                           *
*           X = IMG_sobel(x)    The algorithm is applied to that pixel.     *
*                           The correct output is obtained, the data        *
*                           around the pixels we work on is used            *
*                                                                           *
*           t               Whatever was in the output buffer in that       *
*                           position is kept there.                         *
*                                                                           *
*           z = IMG_sobel(y)    The algorithm is applied to that pixel.     *
*                           The output is not meaningful, because the       *
*                           necessary data to process the pixel is not      *
*                           available.  This is because for each output     *
*                           pixel we need input pixels from the right and   *
*                           from the left of the output pixel.  But this    *
*                           data doesn't exist.                             *
*                                                                           *
*       This means that we will only process (rows-2) lines.  Then, we      *
*       will process all the pixels inside each line. Even though the       *
*       results for the first and last pixels in each line will not         *
*       be relevant, it makes the control much simpler and ends up          *
*       saving cycles.                                                      *
*                                                                           *
*       Also the first pixel in the first processed line and the            *
*       last pixel in the last processed line will not be computed.         *
*       It is not necessary, since the results would be bogus.              *
*                                                                           *
*       The following horizontal and vertical masks that are                *
*       applied to the input buffer to obtain one output pixel.             *
*                                                                           *
*           Horizontal:                                                     *
*               -1 -2 -1                                                    *
*                0  0  0                                                    *
*                1  2  1                                                    *
*                                                                           *
*           Vertical:                                                       *
*               -1  0  1                                                    *
*               -2  0  2                                                    *
*               -1  0  1                                                    *
*                                                                           *
*       This is a C model of the Sobel implementation.  This C code         *
*       is functionally equivalent to the assembly code without             *
*       restrictions.   The assembly code may impose additional             *
*       restrictions.                                                       *
*                                                                           *