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

ExpanDrive 5.4.6 - $49.99
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more
Apple Pages 6.1.1 - Apple's word pr...
Apple Pages is a powerful word processor that gives you everything you need to create documents that look beautiful. And read beautifully. It lets you work seamlessly between Mac and iOS devices, and... Read more
Apple Numbers 4.1.1 - Apple's sprea...
With Apple Numbers, sophisticated spreadsheets are just the start. The whole sheet is your canvas. Just add dramatic interactive charts, tables, and images that paint a revealing picture of your data... Read more
Apple Keynote 7.1.1 - Apple's prese...
Easily create gorgeous presentations with the all-new Keynote, featuring powerful yet easy-to-use tools and dazzling effects that will make you a very hard act to follow. The Theme Chooser lets you... Read more
Espresso 5 - Powerful HTML, XML, CSS, an...
Espresso is back. For people who make delightful, innovative, and fast websites -- in an app to match. Espresso helps you write, code, design, build, and publish with flair and efficiency.... Read more
Vitamin-R 2.47 - Personal productivity t...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more
Dash 4.0.3 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
Posterino 3.3.6 - Create posters, collag...
Posterino offers enhanced customization and flexibility including a variety of new, stylish templates featuring grids of identical or odd-sized image boxes. You can customize the size and shape of... Read more
Together 3.8.3 - Store and organize all...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Features Smart storage. With simple drag-and-drop... Read more
iClock Pro 3.4.9 - Customize your menuba...
iClock Pro is a menu bar replacement clock for Apple's default clock. iClock Pro is an update, total rewrite and improvement to the popular iClock. Have the day, date and time in different fonts and... Read more

Latest Forum Discussions

See All

Minimalist puzzle game, Cuts, free on iO...
If you're looking for a gorgeous puzzle experience on iOS devices, developer Gamebra.in's aesthetically interesting puzzler, Cuts, is discounted to free on the iOS App Store right now. [Read more] | Read more »
Anime tactical RPG, War of Crown, comes...
If you're looking for another tactical RPG fix to go alongside your Fire Emblem Heroes campaigns check out Gamevil's newest, anime-inspired tactics RPG, War of Crown, which comes out tomorrow. [Read more] | Read more »
Fantasy MMORPG MU Origin adds new modes,...
MU Origin, Webzen’s highly popular fantasy MMORPG is getting ready to shake things up for the second time this year, as a new update makes its way to the Google Play and App Store from today. Introducing new systems, modes, and events, the land of... | Read more »
Blizzard is looking to hire a mobile dev...
A new thread on the popular video game rumor forum, NeoGAF, uncovered an interesting job listing over at Blizzard Entertainment. It appears the studio behindStarCraft, World of WarCraft, Hearthstone,andOverwatch is looking to bring on a new hire... | Read more »
Legend of Zelda meets Cooking Mama in ne...
Dungeon Chef is what happens when you mix the RPG elements (and style) of a Legend of Zelda game, with cooking elements. Although, now that The Legend of Zelda: Breath of the Wild also has cookingelements, so maybe the gameplay is not so novel.... | Read more »
ChordFlow (Music)
ChordFlow 1.0.0 Device: iOS Universal Category: Music Price: $6.99, Version: 1.0.0 (iTunes) Description: ChordFlow is a chord sequencer with a unique 4-track polyphonic arpeggiator, extensive chord library, MIDI out and Ableton Link... | Read more »
The Walking Dead: A New Frontier is out...
The newest season of Telltale Games'The Walking Dead is well underway. After the release of the third episode, "Above the Law" about a month ago, episode four, "Thicker Than Water" is hot and ready for more zombies and gut-wrenching emotional... | Read more »
Best games we played this week
Another week, another new wave of mobile games do dive into. We've dug through the list of apps that came out this week to tell you which apps are worth your sweet time. And while there weren't too many games this week, there were some big ones.... | Read more »
Vignettes (Games)
Vignettes 1.0.1 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.1 (iTunes) Description: Vignettes is a casual but unique exploration game without text or characters, where objects shapeshift as you spin them around... | Read more »
Get Me Outta Here is an 80s retro shoote...
Are you ready to fight some aliens? Because Crescent Moon Games has released the retro shooter Get Me Outta Here on iOS devices today. [Read more] | Read more »

Price Scanner via MacPrices.net

HyperX Ships Pulsefire FPS Gaming Mouse, Winn...
Your reporter is a longtime fan of gaming mice for general purpose coomnputing use, finding them typically superior in comfort and performance. HyperX, a division of Kingston Technology Company, Inc... Read more
Penske Truck Leasing Unveils “Penske Fleet” M...
Penske Truck Leasing has introduced a free mobile app called “Penske Fleet” to benefit its full-service truck leasing and contract maintenance customers. The mobile app enables Penske’s customers to... Read more
DEVONthink To Go 2.1.3 For iOS Adds New Declu...
DEVONtechnologies has updated DEVONthink To Go, its iOS companion to DEVONthink for Mac. Enhancements and bug fixes in Version 2.1.3 include DEVONtechnologies’ new decluttering service for clipping... Read more
Use Apple’s Education discount to save up to...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free: -... Read more
Apple refurbished Apple Watches available sta...
Apple is now offering Certified Refurbished Series 1 and Series 2 Apple Watches for 14-16% off MSRP, starting at $229. An Apple one-year warranty is included with each watch. Shipping is free: Series... Read more
15-inch Touch Bar MacBook Pros, Apple refurbi...
Apple is offering Certified Refurbished 2016 15″ Touch Bar MacBook Pros for $360 to $420 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2.6GHz... Read more
13-inch MacBook Airs on sale for up to $150 o...
Overstock.com has 13″ MacBook Airs on sale for up to $150 off MSRP including free shipping: - 13″ 1.6GHz/128GB MacBook Air (sku MMGF2LL/A): $869.99 $130 off MSRP - 13″ 1.6GHz/256GB MacBook Air (sku... Read more
15-inch Touch Bar MacBook Pros on sale for $1...
B&H Photo has the new 2016 15″ Apple Touch Bar MacBook Pros in stock today and on sale for up to $200 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.7GHz Touch Bar... Read more
15-inch 2.7GHz Touch Bar MacBook Pros on sale...
Amazon has 2016 15″ 2.7GHz Apple Touch Bar MacBook Pros in stock today and on sale for $150-$200 off MSRP. Shipping is free: - 15″ 2.7GHz Touch Bar MacBook Pro Space Gray (sku MLH42LL/A): $2599 $200... Read more
Apple now offering Certified Refurbished 13-i...
Apple is now offering Certified Refurbished 2016 13″ Touch Bar MacBook Pros for $270-$300 off original MSRP. An Apple one-year warranty is included with each model, and shipping is free: - 13″ 2.9GHz... Read more

Jobs Board

*Apple* Engineering Specialist - CSRA (Unite...
Apple Engineering Specialist All times are in Eastern Daylight Time Requisition ID Job Locations US DC Washington DC Posted Date Category Engineering Sciences Read more
*Apple* Mac Computer Technician - GeekHampto...
…complex computer issues over the phone and in person? GeekHampton, Long Island's Apple Premium Service Provider, is looking for you! Come work with our crew 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
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 56881986 Middletown, NY, New York, United States Posted: Apr. 17, 2017 Weekly Hours: 40.00 **Job Summary** As an Apple Read more
*Apple* Mobile Master - Best Buy (United Sta...
**489879BR** **Job Title:** Apple Mobile Master **Location Number:** 000402-Utica-Store **Job Description:** **What does a Best Buy Apple Mobile Master do?** At Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.