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];
      }
    }
  }
}
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Hopper Disassembler 4.2.19- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
Duet 1.6.5.5 - Use your iPad as an exter...
Duet is the first app that allows you to use your iDevice as an extra display for your Mac using the Lightning or 30-pin cable. Note: This app requires a $14.99 iOS companion app. Version 1.6.5.5:... Read more
Monosnap 3.4.0 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with our... Read more
Tweetbot 2.5.3 - Popular Twitter client.
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Default Folder X 5.1.6 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Evernote 6.12.3 - Create searchable note...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
Geekbench 4.1.2 - Measure processor and...
Geekbench provides a comprehensive set of benchmarks engineered to quickly and accurately measure processor and memory performance. Designed to make benchmarks easy to run and easy to understand,... Read more
Carbon Copy Cloner 5.0.2 - Easy-to-use b...
Carbon Copy Cloner backups are better than ordinary backups. Suppose the unthinkable happens while you're under deadline to finish a project: your Mac is unresponsive and all you hear is an ominous,... Read more
BetterTouchTool 2.305 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
calibre 3.8.0 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more

The best new games we played this week -...
It's pretty much been one big release after another. We were privy to a bunch of surprises this week, with a lot of games we'd been waiting for quite some time dropping unexpectedly. We hope you're free this weekend, because there is a lot for... | Read more »
Stormbound: Kingdom Wars guide - how to...
Stormbound: Kingdom Wars is an excellent new RTS turned card battler out now on iOS and Android. Lovers of strategy will get a lot of enjoyment out of Stormbound's chess-like mechanics, and it's cardbased units are perfect for anyone who loves the... | Read more »
The best AR apps and games on iOS right...
iOS 11 has officially launched, and with it comes Apple's ARKit, a helpful framework that makes it easier than ever for developers to create mobile AR experiences. To celebrate the occassion, we're featuring some of the best AR apps and games on... | Read more »
Phoenix Wright: Ace Attorney - Spirit of...
Phoenix Wright: Ace Attorney - Spirit of Justice 1.00.00 Device: iOS Universal Category: Games Price: $.99, Version: 1.00.00 (iTunes) Description: ************************************************※IMPORTANT※・Please read the “When... | Read more »
Kpressor (Utilities)
Kpressor 1.0.0 Device: iOS Universal Category: Utilities Price: $4.99, Version: 1.0.0 (iTunes) Description: The ultimate ZIP compression application for iPhone and iPad. - Full integration of iOS 11 with support for multitasking.-... | Read more »
Find out how you can save £35 and win a...
Nothing raises excitement like a good competition, and we’re thrilled to announce our latest contest. We’ll be sending one lucky reader and a friend to the Summoners War World Arena Championship at Le Comedia in Paris on October 7th. It’s the... | Read more »
Another Lost Phone: Laura's Story...
Another Lost Phone: Laura's Story 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Another Lost Phone is a game about exploring the social life of a young woman whose phone you have just... | Read more »
The Witness (Games)
The Witness 1.0 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0 (iTunes) Description: You wake up, alone, on a strange island full of puzzles that will challenge and surprise you. You don't remember who you are, and... | Read more »
Egg, Inc. guide - how to build your gold...
Egg, Inc.'s been around for some time now, but don't you believe for one second that this quirky clicker game has gone out of style. The game keeps popping up on Reddit and other community forums thanks to the outlandish gameplay (plus, the... | Read more »
The best deals on the App Store this wee...
Good news, everyone! Your favorite day of the week has arrived at last -- it's discount roundup day! This fine Wednesday evening we're gathering up the hottest deals on the App Store. We've got action platformers, we've got puzzle games, we've got... | Read more »

Price Scanner via MacPrices.net

Looking for a 2017 12″ Retina MacBook? Save $...
Apple has Certified Refurbished 2017 12″ Retina MacBooks available for $200-$240 off the cost of new models. Apple will include a standard one-year warranty with each MacBook, and shipping is free.... Read more
Apple Offering Up To $455 Credit Toward iPhon...
iPhone 8 and 8 Plus are now available at the Apple Store, and you can receive up to $375 credit toward a new iPhone purchase when you trade in your eligible smartphone. Photo Courtesy Apple Just... Read more
AnyTrans Offers iOS Users Three Ways For Movi...
iMobie Inc. today announceed AnyTrans v6.0.1, which now can help iOS users move all data to iPhone 8/8 Plus seamlessly. The software is available both on Mac and Windows and fully able to move all... Read more
Snag a 13-inch 2.3GHz MacBook Pro for $100 of...
B&H Photo has 2017 13″ 2.3GHz MacBook Pros in stock today and on sale for $100 off MSRP, each including free shipping plus NY & NJ sales tax only: – 13-inch 2.3GHz/128GB Space Gray MacBook... Read more
Verizon offers new iPhone 8 for $100-$300 off...
Verizon is offering the new iPhone 8 for up to $300 off MSRP with an eligible trade-in: • $300 off: iPhone 6S/6S Plus/7/7 Plus, Google Pixel XL, LG G6, Moto Z2 Force, Samsung Galaxy S7/S7 edge/S8/S8... Read more
Apple Refurbished 2017 13-inch MacBook Pros a...
Apple has Certified Refurbished 2017 13″ Touch Bar MacBook Pros in stock today and available for $200-$300 off MSRP. A standard Apple one-year warranty is included with each MacBook, and shipping is... Read more
OWC USB-C Travel Dock with 5 Ports Connectivi...
OWC have announced the new OWC USB-C Travel Dock, the latest addition to their line of connectivity solutions. The USB-C Travel Dock lets you connect its integrated USB-C cable to a Mac or PC laptop... Read more
Pelican Products, Inc. Unveils Cases For All...
Pelican Products, Inc. has announced the launch of its full line of cases including Voyager, Adventurer, Protector, Ambassador, Interceptor (for the Apple iPhone 8 and 8 Plus backwards compatible... Read more
$100 off new 2017 13-inch MacBook Airs
B&H Photo has 2017 13″ MacBook Airs on sale today for $100 off MSRP including free shipping. B&H charges NY & NJ sales tax only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off... Read more
Apple restocks Certified Refurbished 13-inch...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $719 and 2016 models available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is... Read more

Jobs Board

Instructional Designer, *Apple* Product Doc...
Job Summary The Apple Product Documentation team is looking for an instructional designer or a video editor to write user documentation for its professional video Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with Tennessee Interviews but with Apple , Inc. Tennessee Interviews is a private organization that works in collaboration with Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with South Carolina Interviews but with Apple , Inc. South Carolina Interviews is a private organization that works in collaboration Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.