TweetFollow Us on Twitter

Jul 94 Challenge
Volume Number:10
Issue Number:7
Column Tag:Programmers’ Challenge

Programmers’ Challenge

By Mike Scanlin, MacTech Magazine Regular Contributing Author

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Color Space Conversion

Typically, when an RGB image is compressed into JPEG data, it is first converted into separate luminance (Y) and chrominance (U and V) components. Although JPEG doesn’t specify which color space conversion to use, a commonly used one is:

Y     0.29900000   0.58700000   0.11400000     R
U  = -0.16873590  -0.33126410   0.50000000  *  G
V     0.50000000  -0.41868760  -0.08131241     B

where R, G and B are unsigned chars (0..255). For the outputs, Y is an unsigned char (0..255) while U and V are signed chars (-128..127).

The prototype of the two functions you write are:


/* 1 */
void *RGBtoYUVInit(void);

void RGBtoYUV(rPtr, gPtr, bPtr, 
              yPtr, uPtr, vPtr,
              numPixels,privateDataPtr)
unsigned char *rPtr;
unsigned char *gPtr;
unsigned char *bPtr;
unsigned char *yPtr;
  signed char *uPtr;
  signed char *vPtr;
unsigned long numPixels;
         void *privateDataPtr;

This month you’re being given a chance to have a separate initialization routine that will not be timed (only the RGBtoYUV will count towards your time). It can create whatever lookup tables RGBtoYUV may need and return a pointer to that private data. The return value from RGBtoYUVInit will be passed to RGBtoYUV as the privateDataPtr parameter. You decide what it points to (if anything).

There are two key aspects to writing RGBtoYUV. The first is that it has to be fast (as always). The second, though, is that it has to be accurate (or else when someone reconstructs the image with the inverse conversion image quality will be lost). Even though the outputs are only 8 bits, the matrix coefficients require much more than that to represent. Your output values must equal what you would get if you carried out the matrix math with complete precision and then rounded the results down to 8 bits as the last step (with .5 rounding down to zero). For instance, if R = 3, G = 17 and B = 23 then: Y = 3*.299 + 17*.587 + 23*.114 which is 13.498. When rounded this becomes 13 which is what you should return as part of the buffer that yPtr points to.

Each of the pointers to the RGB input data and YUV output data point to a buffer filled with data of one component (so there are 6 buffers total). numPixels is between 1 and 1,000,000 and is the size of each buffer. If numPixels were 100 then rPtr would point to 100 red values and gPtr and bPtr would point to 100 corresponding green and blue values. Your routine would then set the 100 bytes pointed to by yPtr to the appropriate Y values (and likewise for the U and V values, too).

The RGB and YUV buffers will be allocated for you. Your initialization routine may allocate up to 1MB of lookup tables if it wants to (it will be able to get a contiguous 1MB piece if it needs it).

TWO MONTHS AGO WINNER

We have a new first-time winner this month. Congrats to Troy Anderson (Paradise Valley, AZ) for his somewhat large but definitely fast entry in the Flip Horizontal challenge. He was faster than second place winner Bob Boonstra (Westford, MA) in every case that I tested. No small feat considering that Bob is a three-time Challenge winner. Troy also beat another three-time winner, Bill Karsh (Chicago, IL), in almost every test case. Unfortunately, Bill may have been too ecstatic with his win last month to test every possible case this month and unfortunately I had to disqualify his entry for lack of correctness.

Here are the code sizes and times. The time numbers represents the sum of the times for many different inputs (different depths, different rowBytes, etc). Numbers in parens after a person’s name indicate how many times that person has finished in the top 5 places of all previous Programmer Challenges, not including this one:

Name time code+data

Troy Anderson 759 2442

Bob Boonstra (8) 818 1564

Allen Stenger (5) 1069 1318

Michael Panchenko 2952 616

The best way to do well at the Flip Horizontal problem is to write dedicated code to handle each possible depth. That’s exactly what Troy did. He then went even further by special casing certain common cases, such as when rowBytes is a multiple of four.

Troy also solved the flip-byte problem (that exists when the depth is less than 8) the same way that almost everyone else did: with a lookup table for each case (1-bit, 2-bit and 4-bit). For example, when you’re flipping a bitmap horizontally it becomes necessary to flip all 8 bits in a byte. With a 256 element lookup table you can do this in a single lookup.

The 8-bit, 16-bit and 32-bit deep cases are all very similar. Troy reuses similar code by letting the preprocessor fill in the types of his variables (he uses the #define T for this purpose).

Another way of doing this, if the code is similar enough for each case, is to make the whole routine a macro and have it take a parameter which represents the type (byte, short, etc) that you want the code generated for. For instance, Bob Boonstra created this macro:


/* 2 */
/* Macro DoFlipHoriz 
 handles cases where a pixel is one byte, word, or longword in size.
 */
#define DoFlipHoriz(tp) \
{ \
/* loopCount=numCols/2 has already been calculated. */ \
  if (0 < loopCount) do { \
    register tp *p,*q; \
    p = (tp *)base; \
    q = p+numCols; \
    cCount = loopCount; \
    do { \
      register tp temp; \
      temp = *p; \
      *p++ = *--q; \
      *q = temp; \
    } while (--cCount); \
    base += rowBytes; \
  } while (--rCount); \
}
and then uses it like this in part of his solution:

    register short cCount,rCount,loopCount;
    rCount = numRows;
    loopCount = numCols>>1;
    if (8 == pixSize) DoFlipHoriz(uchar) 
    else if (16==pixSize) DoFlipHoriz(ushort)
    else /*if (32==pixSize)*/ DoFlipHoriz(ulong)

You’ll get 3 copies of the macro’s code, each for a different size pixel.
Here’s Troy’s winning solution:

// MacTech Magazine Programmers' Challenge
// May, 1994
// Submitted by Troy Anderson
// 
// Copyright (c) 1994 Troy L. Anderson

#include <QDOffscreen.h>

typedef unsigned char UCHAR;

prototypes
void FlipPixMapHorz( PixMapHandle thePixMapHndl);

static void Flip_Long(  PixMapHandle theMap, 
                        short rowBytes,
                        short depth,
                        Rect* area);

static void Flip_Word(  PixMapHandle theMap, 
                        short rowBytes,
                        short depth,
                        Rect* area);

static void ExchangeWords_Long( PixMapHandle theMap, 
                                short rowBytes,
                                short depth,
                                Rect* area);

static void ExchangeWords_Word( PixMapHandle theMap, 
                                short rowBytes,
                                short depth,
                                Rect* area);

static void ExchangeWords_Byte( PixMapHandle theMap, 
                                short rowBytes,
                                short depth,
                                Rect* area);


FlipPixMapHorz
// This could be made a bit faster by in-lining the functions, but this 
is much clearer,
// and not very much slower.
void FlipPixMapHorz( PixMapHandle thePixMapHndl)
{
  short   rowBytes = (**thePixMapHndl).rowBytes & 0x7fff;
  Boolean longAligned = rowBytes % 4 == 0;
  short   depth = (**thePixMapHndl).pixelSize;
  Rect    bounds = (**thePixMapHndl).bounds;
  
  switch( depth)
  {
    case  1:
    case  2:
    case  4:
      if (longAligned)
        Flip_Long(  thePixMapHndl, 
                    rowBytes,
                    depth,
                    &bounds);
      else
        Flip_Word(  thePixMapHndl,
                    rowBytes,
                    depth,
                    &bounds);
      break;

    case  8:
      ExchangeWords_Byte( thePixMapHndl,
                          rowBytes,
                          depth,
                          &bounds);
      break;
    
    case  16:
      ExchangeWords_Word( thePixMapHndl,
                          rowBytes,
                          depth,
                          &bounds);
      break;
      
    case  32:
      ExchangeWords_Long( thePixMapHndl,
                          rowBytes,
                          depth,
                          &bounds);
      break;
  }
}


ExchangeWords_Long
long word alignment version
static void ExchangeWords_Long( PixMapHandle theMap,
                                short rowBytes,
                                short depth,
                                Rect* area)
{
#undef T
#define T long

  short       rowCells = rowBytes / sizeof(T);
  short       numCells = ((area->right - area->left) * 
                      depth + sizeof(T)*8 - 1) / 
                      (sizeof(T)*8);
  T           temp;
  register T  *cellPtr1, *cellPtr2;
  T           *aRow;
  T           *firstRow = (T*)GetPixBaseAddr( theMap);
  T           *lastRow = firstRow + rowCells * 
                        (long)(area->bottom - area->top);

    // Flip the words in each row
  for ( aRow = firstRow; aRow < lastRow; aRow += rowCells)
    for ( cellPtr1 = aRow + numCells-1, cellPtr2 = aRow;
        cellPtr1 > cellPtr2; 
        cellPtr1--, cellPtr2++)
      temp = *cellPtr1, // swap them 
      *cellPtr1 = *cellPtr2, 
      *cellPtr2 = temp;
}


ExchangeWords
word alignment version
static void ExchangeWords_Word( PixMapHandle theMap,
                                short rowBytes,
                                short depth,
                                Rect* area)
{
#undef T
#define T short

  short       rowCells = rowBytes / sizeof(T);
  short       numCells = ((area->right - area->left) * 
                      depth + sizeof(T)*8 - 1) / 
                      (sizeof(T)*8);
  T           temp;
  register T  *cellPtr1, *cellPtr2;
  T           *aRow;
  T           *firstRow = (T*)GetPixBaseAddr( theMap);
  T           *lastRow = firstRow + rowCells * 
                        (long)(area->bottom - area->top);

    // Flip the words in each row
  for ( aRow = firstRow; aRow < lastRow; aRow += rowCells)
    for ( cellPtr1 = aRow + numCells-1, cellPtr2 = aRow;
        cellPtr1 > cellPtr2; 
        cellPtr1--, cellPtr2++)
      temp = *cellPtr1, // swap them 
      *cellPtr1 = *cellPtr2, 
      *cellPtr2 = temp;
}

ExchangeWords
byte alignment version
static void ExchangeWords_Byte( PixMapHandle theMap,
                                short rowBytes,
                                short depth,
                                Rect* area)
{
#undef T
#define T char

  short       rowCells = rowBytes / sizeof(T);
  short       numCells = ((area->right - area->left) * 
                      depth + sizeof(T)*8 - 1) / 
                      (sizeof(T)*8);
  T           temp;
  register T  *cellPtr1, *cellPtr2;
  T           *aRow;
  T           *firstRow = (T*)GetPixBaseAddr( theMap);
  T           *lastRow = firstRow + rowCells * 
                        (long)(area->bottom - area->top);

    // Flip the words in each row
  for ( aRow = firstRow; aRow < lastRow; aRow += rowCells)
    for ( cellPtr1 = aRow + numCells-1, cellPtr2 = aRow;
        cellPtr1 > cellPtr2; 
        cellPtr1--, cellPtr2++)
      temp = *cellPtr1, // swap them 
      *cellPtr1 = *cellPtr2, 
      *cellPtr2 = temp;
}


Inverse tables
// Inverse tables used to flip the bits in a byte - 
// index is input, value is inverse of index

// This is the 1-bit per pixel table
static char byteFlips1[] ={ 
  0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 
  0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
  0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8, 
  0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
  0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4, 
  0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4, 
  0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 
  0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc, 
  0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2, 
  0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2, 
  0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea, 
  0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa, 
  0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 
  0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6, 
  0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee, 
  0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe, 
  0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1, 
  0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1, 
  0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, 
  0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9, 
  0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5, 
  0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5, 
  0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed, 
  0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
  0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, 
  0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
  0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb, 
  0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb, 
  0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7, 
  0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7, 
  0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, 
  0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff  };
              
// This is the 2-bits per pixel table
static char byteFlips2[] ={ 
  0x00, 0x40, 0x80, 0xc0, 0x10, 0x50, 0x90, 0xd0, 
  0x20, 0x60, 0xa0, 0xe0, 0x30, 0x70, 0xb0, 0xf0,
  0x04, 0x44, 0x84, 0xc4, 0x14, 0x54, 0x94, 0xd4, 
  0x24, 0x64, 0xa4, 0xe4, 0x34, 0x74, 0xb4, 0xf4,
  0x08, 0x48, 0x88, 0xc8, 0x18, 0x58, 0x98, 0xd8, 
  0x28, 0x68, 0xa8, 0xe8, 0x38, 0x78, 0xb8, 0xf8, 
  0x0c, 0x4c, 0x8c, 0xcc, 0x1c, 0x5c, 0x9c, 0xdc, 
  0x2c, 0x6c, 0xac, 0xec, 0x3c, 0x7c, 0xbc, 0xfc, 
  0x01, 0x41, 0x81, 0xc1, 0x11, 0x51, 0x91, 0xd1, 
  0x21, 0x61, 0xa1, 0xe1, 0x31, 0x71, 0xb1, 0xf1, 
  0x05, 0x45, 0x85, 0xc5, 0x15, 0x55, 0x95, 0xd5, 
  0x25, 0x65, 0xa5, 0xe5, 0x35, 0x75, 0xb5, 0xf5, 
  0x09, 0x49, 0x89, 0xc9, 0x19, 0x59, 0x99, 0xd9, 
  0x29, 0x69, 0xa9, 0xe9, 0x39, 0x79, 0xb9, 0xf9, 
  0x0d, 0x4d, 0x8d, 0xcd, 0x1d, 0x5d, 0x9d, 0xdd, 
  0x2d, 0x6d, 0xad, 0xed, 0x3d, 0x7d, 0xbd, 0xfd, 
  0x02, 0x42, 0x82, 0xc2, 0x12, 0x52, 0x92, 0xd2, 
  0x22, 0x62, 0xa2, 0xe2, 0x32, 0x72, 0xb2, 0xf2, 
  0x06, 0x46, 0x86, 0xc6, 0x16, 0x56, 0x96, 0xd6, 
  0x26, 0x66, 0xa6, 0xe6, 0x36, 0x76, 0xb6, 0xf6, 
  0x0a, 0x4a, 0x8a, 0xca, 0x1a, 0x5a, 0x9a, 0xda, 
  0x2a, 0x6a, 0xaa, 0xea, 0x3a, 0x7a, 0xba, 0xfa, 
  0x0e, 0x4e, 0x8e, 0xce, 0x1e, 0x5e, 0x9e, 0xde, 
  0x2e, 0x6e, 0xae, 0xee, 0x3e, 0x7e, 0xbe, 0xfe, 
  0x03, 0x43, 0x83, 0xc3, 0x13, 0x53, 0x93, 0xd3, 
  0x23, 0x63, 0xa3, 0xe3, 0x33, 0x73, 0xb3, 0xf3, 
  0x07, 0x47, 0x87, 0xc7, 0x17, 0x57, 0x97, 0xd7, 
  0x27, 0x67, 0xa7, 0xe7, 0x37, 0x77, 0xb7, 0xf7, 
  0x0b, 0x4b, 0x8b, 0xcb, 0x1b, 0x5b, 0x9b, 0xdb, 
  0x2b, 0x6b, 0xab, 0xeb, 0x3b, 0x7b, 0xbb, 0xfb, 
  0x0f, 0x4f, 0x8f, 0xcf, 0x1f, 0x5f, 0x9f, 0xdf, 
  0x2f, 0x6f, 0xaf, 0xef, 0x3f, 0x7f, 0xbf, 0xff  };
            
// This is the 4-bits per pixel table
static char byteFlips4[] ={ 
  0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70, 
  0x80, 0x90, 0xa0, 0xb0, 0xc0, 0xd0, 0xe0, 0xf0,
  0x01, 0x11, 0x21, 0x31, 0x41, 0x51, 0x61, 0x71, 
  0x81, 0x91, 0xa1, 0xb1, 0xc1, 0xd1, 0xe1, 0xf1, 
  0x02, 0x12, 0x22, 0x32, 0x42, 0x52, 0x62, 0x72, 
  0x82, 0x92, 0xa2, 0xb2, 0xc2, 0xd2, 0xe2, 0xf2, 
  0x03, 0x13, 0x23, 0x33, 0x43, 0x53, 0x63, 0x73, 
  0x83, 0x93, 0xa3, 0xb3, 0xc3, 0xd3, 0xe3, 0xf3, 
  0x04, 0x14, 0x24, 0x34, 0x44, 0x54, 0x64, 0x74, 
  0x84, 0x94, 0xa4, 0xb4, 0xc4, 0xd4, 0xe4, 0xf4, 
  0x05, 0x15, 0x25, 0x35, 0x45, 0x55, 0x65, 0x75, 
  0x85, 0x95, 0xa5, 0xb5, 0xc5, 0xd5, 0xe5, 0xf5, 
  0x06, 0x16, 0x26, 0x36, 0x46, 0x56, 0x66, 0x76, 
  0x86, 0x96, 0xa6, 0xb6, 0xc6, 0xd6, 0xe6, 0xf6, 
  0x07, 0x17, 0x27, 0x37, 0x47, 0x57, 0x67, 0x77, 
  0x87, 0x97, 0xa7, 0xb7, 0xc7, 0xd7, 0xe7, 0xf7, 
  0x08, 0x18, 0x28, 0x38, 0x48, 0x58, 0x68, 0x78, 
  0x88, 0x98, 0xa8, 0xb8, 0xc8, 0xd8, 0xe8, 0xf8, 
  0x09, 0x19, 0x29, 0x39, 0x49, 0x59, 0x69, 0x79, 
  0x89, 0x99, 0xa9, 0xb9, 0xc9, 0xd9, 0xe9, 0xf9, 
  0x0a, 0x1a, 0x2a, 0x3a, 0x4a, 0x5a, 0x6a, 0x7a, 
  0x8a, 0x9a, 0xaa, 0xba, 0xca, 0xda, 0xea, 0xfa, 
  0x0b, 0x1b, 0x2b, 0x3b, 0x4b, 0x5b, 0x6b, 0x7b, 
  0x8b, 0x9b, 0xab, 0xbb, 0xcb, 0xdb, 0xeb, 0xfb, 
  0x0c, 0x1c, 0x2c, 0x3c, 0x4c, 0x5c, 0x6c, 0x7c, 
  0x8c, 0x9c, 0xac, 0xbc, 0xcc, 0xdc, 0xec, 0xfc, 
  0x0d, 0x1d, 0x2d, 0x3d, 0x4d, 0x5d, 0x6d, 0x7d, 
  0x8d, 0x9d, 0xad, 0xbd, 0xcd, 0xdd, 0xed, 0xfd, 
  0x0e, 0x1e, 0x2e, 0x3e, 0x4e, 0x5e, 0x6e, 0x7e, 
  0x8e, 0x9e, 0xae, 0xbe, 0xce, 0xde, 0xee, 0xfe, 
  0x0f, 0x1f, 0x2f, 0x3f, 0x4f, 0x5f, 0x6f, 0x7f, 
  0x8f, 0x9f, 0xaf, 0xbf, 0xcf, 0xdf, 0xef, 0xff  };


Flip_Long
static void Flip_Long(  PixMapHandle theMap, 
                        short rowBytes,
                        short depth,
                        Rect* area)
{
#undef T
#define T long

  register UCHAR  temp;
  short           rowCells = rowBytes / sizeof(T);
  long            bitsPerRow = (area->right - area->left) *
                          (long)depth - 1;
  short           numCells = (bitsPerRow + sizeof(T)*8) /
                          (sizeof(T)*8);
  T*              cellPtr;
  T*              aRow;
  T*              firstRow = (T*)GetPixBaseAddr( theMap);
  T*              lastRow = firstRow + rowCells * 
                      (long)(area->bottom - area->top);
  
  register T*     cellPtr1, *cellPtr2;

  short           numBitsToShift = ((sizeof(T)*8) -
                      (bitsPerRow % (sizeof(T)*8) + 1));
  T               shiftMask;
  T*              shiftCellPtr;
  char*           flipTable;
  
  

  switch(depth)
  {
    case 1:
      flipTable = byteFlips1;
      break;
    case 2:
      flipTable = byteFlips2;
      break;
    case 4:
      flipTable = byteFlips4;
      break;
  }
            

  if (numBitsToShift)
  {
    shiftMask = (1L << numBitsToShift) - 1;

    for ( aRow = firstRow; 
        aRow < lastRow;
        aRow += rowCells)
    {
      // With each pair of cells in the row (one on the left, the other 
on the right),
      // flip the pixels in the individual cells and swap the cells with 
one another.
      for ( cellPtr1 = aRow + numCells - 1, cellPtr2 = aRow;
          cellPtr1 > cellPtr2;
          cellPtr1--, cellPtr2++)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] = 
            flipTable[((UCHAR*)cellPtr2)[3]];
        ((UCHAR*)cellPtr2)[3] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[1];
        ((UCHAR*)cellPtr1)[1] = 
            flipTable[((UCHAR*)cellPtr2)[2]];
        ((UCHAR*)cellPtr2)[2] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[2];
        ((UCHAR*)cellPtr1)[2] = 
            flipTable[((UCHAR*)cellPtr2)[1]];
        ((UCHAR*)cellPtr2)[1] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[3];
        ((UCHAR*)cellPtr1)[3] = 
            flipTable[((UCHAR*)cellPtr2)[0]];
        ((UCHAR*)cellPtr2)[0] = flipTable[temp];
      }
      
      // If there's an odd number of cells in the row,  there is one 
cell we haven't
      // touched.   It needs to be flipped.
      if (cellPtr1 == cellPtr2)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] = 
            flipTable[((UCHAR*)cellPtr1)[3]];
        ((UCHAR*)cellPtr1)[3] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[1];
        ((UCHAR*)cellPtr1)[1] = 
            flipTable[((UCHAR*)cellPtr1)[2]];
        ((UCHAR*)cellPtr1)[2] = flipTable[temp];
      }

      // Slide the pixels to the left
      for ( shiftCellPtr = aRow;
          shiftCellPtr < aRow + rowCells;
          shiftCellPtr++)
      {
        // shift the bits over
        *shiftCellPtr <<= numBitsToShift;
          
        // bring in the bits from the next cell - garbage will be brought 
in during
        // the last iteration, but it’s put into the last cell, outside 
the bounds of the 
        // image (but still in the data area)
        *shiftCellPtr |= shiftMask & 
                        (*(shiftCellPtr+1) >> 
                          (sizeof(T)*8 - numBitsToShift));
      }
    }
  }
  else  // no need to shift pixels, otherwise, just the same as previous 
loop
    for ( aRow = firstRow; aRow < lastRow; aRow += rowCells)
    {
      // With each pair of cells in the row (one on the  left, the other 
on the right),
      // flip the pixels in the individual cells and swap the cells with 
one another.
      for ( cellPtr1 = aRow + numCells - 1, cellPtr2 = aRow;
            cellPtr1 > cellPtr2;
            cellPtr1--, cellPtr2++)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] =
            flipTable[((UCHAR*)cellPtr2)[3]];
        ((UCHAR*)cellPtr2)[3] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[1];
        ((UCHAR*)cellPtr1)[1] = 
            flipTable[((UCHAR*)cellPtr2)[2]];
        ((UCHAR*)cellPtr2)[2] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[2];
        ((UCHAR*)cellPtr1)[2] = 
            flipTable[((UCHAR*)cellPtr2)[1]];
        ((UCHAR*)cellPtr2)[1] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[3];
        ((UCHAR*)cellPtr1)[3] = 
            flipTable[((UCHAR*)cellPtr2)[0]];
        ((UCHAR*)cellPtr2)[0] = flipTable[temp];
      }
      
      // If there are an odd number of cells in the row,
      // there is one cell we haven't touched.
      // It needs to be flipped.
      if (cellPtr1 == cellPtr2)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] = 
            flipTable[((UCHAR*)cellPtr1)[3]];
        ((UCHAR*)cellPtr1)[3] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[1];
        ((UCHAR*)cellPtr1)[1] = 
            flipTable[((UCHAR*)cellPtr1)[2]];
        ((UCHAR*)cellPtr1)[2] = flipTable[temp];
      }
    }
  }
}


Flip_Word
static void Flip_Word(  PixMapHandle theMap, 
                        short rowBytes,
                        short depth,
                        Rect* area)
{
#undef T
#define T short

  register UCHAR  temp;
  short           rowCells = rowBytes / sizeof(T);
  long            bitsPerRow = (area->right - area->left) *
                          (long)depth - 1;
  short           numCells = (bitsPerRow + sizeof(T)*8) /
                          (sizeof(T)*8);
  T*              cellPtr;
  T*              aRow;
  T*              firstRow = (T*)GetPixBaseAddr( theMap);
  T*              lastRow = firstRow + rowCells * 
                      (long)(area->bottom - area->top);
  
  register T*     cellPtr1, *cellPtr2;

  short           numBitsToShift = ((sizeof(T)*8) -
                      (bitsPerRow % (sizeof(T)*8) + 1));
  T               shiftMask;
  T*              shiftCellPtr;
  char*           flipTable;
  
  

  switch(depth)
  {
    case 1:
      flipTable = byteFlips1;
      break;
    case 2:
      flipTable = byteFlips2;
      break;
    case 4:
      flipTable = byteFlips4;
      break;
  }
            

  if (numBitsToShift)
  {
    shiftMask = (1L << numBitsToShift) - 1;

    for ( aRow = firstRow; aRow < lastRow; aRow += rowCells)
    {
      // With each pair of cells in the row (one on the left, the other 
on the right),
      // flip the pixels in the individual cells and swap the cells with 
one another.
      for ( cellPtr1 = aRow + numCells - 1, cellPtr2 = aRow;
          cellPtr1 > cellPtr2;
          cellPtr1--, cellPtr2++)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] = 
            flipTable[((UCHAR*)cellPtr2)[1]];
        ((UCHAR*)cellPtr2)[1] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[1];
        ((UCHAR*)cellPtr1)[1] =
            flipTable[((UCHAR*)cellPtr2)[0]];
        ((UCHAR*)cellPtr2)[0] = flipTable[temp];
      }
      
      // If there's an odd number of cells in the row, there is one cell 
we haven't
      // touched.   It needs to be flipped.
      if (cellPtr1 == cellPtr2)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] = 
            flipTable[((UCHAR*)cellPtr1)[1]];
        ((UCHAR*)cellPtr1)[1] = 
            flipTable[temp];
      }

      // Slide the pixels to the left
      for ( shiftCellPtr = aRow;
          shiftCellPtr < aRow + rowCells;
          shiftCellPtr++)
      {
      // shift the bits over
        *shiftCellPtr <<= numBitsToShift;
          
      // bring in the bits from the next cell - garbage will be brought 
in during last 
      // iteration, but it’s put into the last
        // cell, outside the bounds of the image (but still in the data 
area)
        *shiftCellPtr |= shiftMask & 
                        (*(shiftCellPtr+1) >> 
                          (sizeof(T)*8 - numBitsToShift));
      }
    }
  }
  else  // no need to shift pixels, otherwise,  just the same as previous 
loop
    for ( aRow = firstRow; aRow < lastRow; aRow += rowCells)
    {
      // With each pair of cells in the row (one on the 
      // left, the other on the right), flip the pixels
      // in the individual cells and swap the cells with
       // one another.
      for ( cellPtr1 = aRow + numCells - 1, cellPtr2 = aRow;
            cellPtr1 > cellPtr2;
            cellPtr1--, cellPtr2++)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] = 
            flipTable[((UCHAR*)cellPtr2)[1]];
        ((UCHAR*)cellPtr2)[1] = flipTable[temp];
        
        temp = ((UCHAR*)cellPtr1)[1];
        ((UCHAR*)cellPtr1)[1] = 
            flipTable[((UCHAR*)cellPtr2)[0]];
        ((UCHAR*)cellPtr2)[0] = flipTable[temp];
      }
      
      // If there are an odd number of cells in the row,
      // there is one cell we haven't touched.
      // It needs to be flipped.
      if (cellPtr1 == cellPtr2)
      {
        temp = ((UCHAR*)cellPtr1)[0];
        ((UCHAR*)cellPtr1)[0] = 
            flipTable[((UCHAR*)cellPtr1)[1]];
        ((UCHAR*)cellPtr1)[1] = flipTable[temp];
      }
    }
  }
}
 
AAPL
$103.30
Apple Inc.
+0.80
MSFT
$45.09
Microsoft Corpora
-0.34
GOOG
$577.33
Google Inc.
+5.73

MacTech Search:
Community Search:

Software Updates via MacUpdate

TextSoap 7.4.0 - Flexible text editing u...
TextSoap is for people who work with text. TextSoap effortlessly cleans up text from endlessly different formats. Wash away unwanted characters, spaces, tabs. Fix paragraphs with hard returns at the... Read more
NetShade 6.0.2 - Browse privately using...
NetShade is an Internet security tool that conceals your IP address on the web. NetShade routes your Web connection through either a public anonymous proxy server, or one of NetShade's own dedicated... Read more
Mac DVDRipper Pro 5.0 - Copy, backup, an...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
pwSafe 3.1 - Secure password management...
pwSafe provides simple and secure password management across devices and computers. pwSafe uses iCloud to keep your password databases backed-up and synced between Macs and iOS devices. It is... Read more
StatsBar 1.8 - Monitor system processes...
StatsBar gives you a comprehensive and detailed analysis of the following areas of your Mac: CPU usage Memory usage Disk usage Network and bandwidth usage Battery power and health (MacBooks only)... Read more
Path Finder 6.5.5 - Powerful, award-winn...
Path Finder is a file browser that combines the familiar Finder interface with the powerful utilities and innovative features. Just a small selection of the Path Finder 6 feature set: Dual pane... Read more
QuarkXPress 10.2.1 - Desktop publishing...
With QuarkXPress, you can communicate in all the ways you need to -- and always look professional -- in print and digital media, all in a single tool. Features include: Easy to Use -- QuarkXPress is... Read more
Skype 6.19.0.450 - Voice-over-internet p...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
VueScan 9.4.41 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Cloud 3.0.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more

Latest Forum Discussions

See All

Modern Combat 5 Gets a Major Multiplayer...
Modern Combat 5 Gets a Major Multiplayer Update Posted by Jessica Fisher on September 2nd, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Alien Creeps TD Review
Alien Creeps TD Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: EXPENSIVE DEFENSESUniversal App - Designed for iPhone and iPad Alien Creeps TD would be a fun if unremarkable Tower Defense game, but its heavy focus on... | Read more »
The Journey Down: Chapter Two Review
The Journey Down: Chapter Two Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: DARK YET ENTICINGUniversal App - Designed for iPhone and iPad It’s a little dark, in every sense of the word, but The Journey Down:... | Read more »
Function Space, a Social Network App for...
Function Space, a Social Network App for Science, Launches on iOS Posted by Ellis Spice on September 2nd, 2014 [ permalink ] | Read more »
Stupidfast – How Taylor Martinez Switche...
How do you make an Endless Running game more than just another Endless Running game? By adding real life prizes to it, of course! That’s the thinking behind StupidFast: a game designed for football enthusiasts, and the brainchild of former college... | Read more »
Little Raiders: Robin’s Revenge Review
Little Raiders: Robin’s Revenge Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: CASUAL RAIDINGUniversal App - Designed for iPhone and iPad Combining simple combat with village building is a potent combination for... | Read more »
Treasure Tombs: Ra Deal Coming from Bulk...
Treasure Tombs: Ra Deal Coming from Bulkypix and Dark Tonic This Fall Posted by Jessica Fisher on September 2nd, 2014 [ permalink ] Dark Tonic and | Read more »
Pirate Bash Review
Pirate Bash Review By Nadia Oxford on September 2nd, 2014 Our Rating: :: BAD PIRATES, GOOD TIMESUniversal App - Designed for iPhone and iPad Pirate Bash’s turn-based battles add an intriguing twist to a typical physics game.   | Read more »
Tiny Tower Vegas Review
Tiny Tower Vegas Review By Jennifer Allen on September 2nd, 2014 Our Rating: :: STEADY DEVELOPMENTUniversal App - Designed for iPhone and iPad Build a huge tower again but Vegas-style in Tiny Tower Vegas.   | Read more »
The Manhattan Project Review
The Manhattan Project Review By Andrew Fisher on September 2nd, 2014 Our Rating: :: ROCKET SCIENCEUniversal App - Designed for iPhone and iPad The Manhattan Project offers a great Euro-style gameplay experience, but it is totally... | Read more »

Price Scanner via MacPrices.net

Apple refurbished iPads available for up to $...
Apple is offering Certified Refurbished iPad Airs for up to $140 off MSRP. Apple’s one-year warranty is included with each model, and shipping is free. Stock tends to come and go with some of these... Read more
Are We Now In The Post-Post-PC Era?
A longtime and thoroughgoing laptop aficionado, I was more than a little dismayed by Steve Jobs’s declaration back in 2010 when he sprang the iPad on an unsuspecting world. that we’d entered a “post-... Read more
PC Outlook Improves, But 2014 Shipments Still...
According to the International Data Corporation (IDC) Worldwide Quarterly PC Tracker, worldwide PC shipments are expected to fall by -3.7 percent in 2014. To hat’s actually an improvement from the... Read more
IDC Lowers Tablet Sales Projections for 2014...
Following a second consecutive quarter of softer than expected demand, International Data Corporation (IDC) has lowered its worldwide tablet plus 2-in-1 forecast for 2014 to 233.1 million units. The... Read more
Apple now offering refurbished 21-inch 1.4GHz...
The Apple Store is now offering Apple Certified Refurbished 21″ 1.4GHz iMacs for $929 including free shipping plus Apple’s standard one-year warranty. Their price is $170 off the cost of new models,... Read more
Save $50 on the 2.5GHz Mac mini, on sale for...
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more
Save up to $300 on an iMac with Apple refurbi...
The Apple Store has Apple Certified Refurbished iMacs available for up to $300 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more
The Rise of Phablets
Carlisle & Gallagher Consulting Group, a businesses and technology consulting firm focused solely on the financial services industry, has released an infographic depicting the convergence of... Read more
Bad Driver Database App Allows Good Drivers t...
Bad Driver Database 1.4 by Facile Group is a new iOS and Android app that lets users instantly input and see how many times a careless, reckless or just plain stupid driver has been added to the... Read more
Eddy – Cloud Music Player for iPhone/iPad Fre...
Ukraine based CapableBits announces the release of Eddy, its tiny, but smart and powerful cloud music player for iPhone and iPad that allows users to stream or download music directly from cloud... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.