Figure 2 Creating a GDI Palette
//
// Color table created by PalGen.
//
BYTE byVals[8][3] = {
255, 240, 36,
180, 64, 192,
4, 32, 200,
224, 85, 80,
224, 128, 0,
16, 0, 244,
122, 7, 114,
78, 255, 225
};
//
// Code to create a logical palette from the color table.
//
struct {
LOGPALETTE lp;
PALETTEENTRY ape[7]; // Number of palette entries minus 1
} pal;
LOGPALETTE* pLP = (LOGPALETTE*) &pal;
pLP->palVersion = 0x300;
pLP->palNumEntries = 8; // Number of palette entries
for (int i=0; i<pLP->palNumEntries; i++) {
pLP->palPalEntry[i].peRed = byVals[i][0];
pLP->palPalEntry[i].peGreen = byVals[i][1];
pLP->palPalEntry[i].peBlue = byVals[i][2];
pLP->palPalEntry[i].peFlags = 0;
}
HPALETTE hPalette = CreatePalette (pLP);
Figure 3 The CQuantizer Class
Quantize.h
typedef struct _NODE {
BOOL bIsLeaf; // TRUE if node has no children
UINT nPixelCount; // Number of pixels represented by this leaf
UINT nRedSum; // Sum of red components
UINT nGreenSum; // Sum of green components
UINT nBlueSum; // Sum of blue components
struct _NODE* pChild[8]; // Pointers to child nodes
struct _NODE* pNext; // Pointer to next reducible node
} NODE;
class CQuantizer
{
protected:
NODE* m_pTree;
UINT m_nLeafCount;
NODE* m_pReducibleNodes[9];
UINT m_nMaxColors;
UINT m_nColorBits;
public:
CQuantizer (UINT nMaxColors, UINT nColorBits);
virtual ~CQuantizer ();
ProcessImage (HANDLE hImage);
UINT GetColorCount ();
void GetColorTable (RGBQUAD* prgb);
protected:
int GetLeftShiftCount (DWORD dwVal);
int GetRightShiftCount (DWORD dwVal);
void AddColor (NODE** ppNode, BYTE r, BYTE g, BYTE b, UINT nColorBits,
UINT nLevel, UINT* pLeafCount, NODE** pReducibleNodes);
NODE* CreateNode (UINT nLevel, UINT nColorBits, UINT* pLeafCount,
NODE** pReducibleNodes);
void ReduceTree (UINT nColorBits, UINT* pLeafCount,
NODE** pReducibleNodes);
void DeleteTree (NODE** ppNode);
void GetPaletteColors (NODE* pTree, RGBQUAD* prgb, UINT* pIndex);
};
Quantize.cpp
#include "stdafx.h"
#include "Quantize.h"
CQuantizer::CQuantizer (UINT nMaxColors, UINT nColorBits)
{
ASSERT (nColorBits <= 8);
m_pTree = NULL;
m_nLeafCount = 0;
for (int i=0; i<=(int) nColorBits; i++)
m_pReducibleNodes[i] = NULL;
m_nMaxColors = nMaxColors;
m_nColorBits = nColorBits;
}
CQuantizer::~CQuantizer ()
{
if (m_pTree != NULL)
DeleteTree (&m_pTree);
}
BOOL CQuantizer::ProcessImage (HANDLE hImage)
{
DWORD rmask, gmask, bmask;
int rright, gright, bright;
int rleft, gleft, bleft;
BYTE* pbBits;
WORD* pwBits;
DWORD* pdwBits;
BYTE r, g, b;
WORD wColor;
DWORD dwColor;
int i, j;
HDC hdc;
BYTE* pBuffer;
BITMAPINFO bmi;
DIBSECTION ds;
::GetObject (hImage, sizeof (ds), &ds);
int nPad = ds.dsBm.bmWidthBytes - (((ds.dsBmih.biWidth *
ds.dsBmih.biBitCount) + 7) / 8);
switch (ds.dsBmih.biBitCount) {
case 1: // 1-bit DIB
case 4: // 4-bit DIB
case 8: // 8-bit DIB
//
// The strategy here is to use ::GetDIBits to convert the
// image into a 24-bit DIB one scan line at a time. A pleasant
// side effect of using ::GetDIBits in this manner is that RLE-
// encoded 4-bit and 8-bit DIBs will be uncompressed.
//
hdc = ::GetDC (NULL);
pBuffer = new BYTE[ds.dsBmih.biWidth * 3];
::ZeroMemory (&bmi, sizeof (bmi));
bmi.bmiHeader.biSize = sizeof (BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = ds.dsBmih.biWidth;
bmi.bmiHeader.biHeight = ds.dsBmih.biHeight;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 24;
bmi.bmiHeader.biCompression = BI_RGB;
for (i=0; i<ds.dsBmih.biHeight; i++) {
::GetDIBits (hdc, (HBITMAP) hImage, i, 1, pBuffer, &bmi,
DIB_RGB_COLORS);
pbBits = pBuffer;
for (j=0; j<ds.dsBmih.biWidth; j++) {
b = *pbBits++;
g = *pbBits++;
r = *pbBits++;
AddColor (&m_pTree, r, g, b, m_nColorBits, 0, &m_nLeafCount,
m_pReducibleNodes);
while (m_nLeafCount > m_nMaxColors)
ReduceTree (m_nColorBits, &m_nLeafCount,
m_pReducibleNodes);
}
}
delete pBuffer;
::ReleaseDC (NULL, hdc);
break;
case 16: // 16-bit DIB
if (ds.dsBmih.biCompression == BI_BITFIELDS) {
rmask = ds.dsBitfields[0];
gmask = ds.dsBitfields[1];
bmask = ds.dsBitfields[2];
}
else {
rmask = 0x7C00;
gmask = 0x03E0;
bmask = 0x001F;
}
rright = GetRightShiftCount (rmask);
gright = GetRightShiftCount (gmask);
bright = GetRightShiftCount (bmask);
rleft = GetLeftShiftCount (rmask);
gleft = GetLeftShiftCount (gmask);
bleft = GetLeftShiftCount (bmask);
pwBits = (WORD*) ds.dsBm.bmBits;
for (i=0; i<ds.dsBmih.biHeight; i++) {
for (j=0; j<ds.dsBmih.biWidth; j++) {
wColor = *pwBits++;
b = (BYTE) (((wColor & (WORD) bmask) >> bright) << bleft);
g = (BYTE) (((wColor & (WORD) gmask) >> gright) << gleft);
r = (BYTE) (((wColor & (WORD) rmask) >> rright) << rleft);
AddColor (&m_pTree, r, g, b, m_nColorBits, 0, &m_nLeafCount,
m_pReducibleNodes);
while (m_nLeafCount > m_nMaxColors)
ReduceTree (m_nColorBits, &m_nLeafCount, m_pReducibleNodes);
}
pwBits = (WORD*) (((BYTE*) pwBits) + nPad);
}
break;
case 24: // 24-bit DIB
pbBits = (BYTE*) ds.dsBm.bmBits;
for (i=0; i<ds.dsBmih.biHeight; i++) {
for (j=0; j<ds.dsBmih.biWidth; j++) {
b = *pbBits++;
g = *pbBits++;
r = *pbBits++;
AddColor (&m_pTree, r, g, b, m_nColorBits, 0, &m_nLeafCount,
m_pReducibleNodes);
while (m_nLeafCount > m_nMaxColors)
ReduceTree (m_nColorBits, &m_nLeafCount, m_pReducibleNodes);
}
pbBits += nPad;
}
break;
case 32: // 32-bit DIB
if (ds.dsBmih.biCompression == BI_BITFIELDS) {
rmask = ds.dsBitfields[0];
gmask = ds.dsBitfields[1];
bmask = ds.dsBitfields[2];
}
else {
rmask = 0x00FF0000;
gmask = 0x0000FF00;
bmask = 0x000000FF;
}
rright = GetRightShiftCount (rmask);
gright = GetRightShiftCount (gmask);
bright = GetRightShiftCount (bmask);
pdwBits = (DWORD*) ds.dsBm.bmBits;
for (i=0; i<ds.dsBmih.biHeight; i++) {
for (j=0; j<ds.dsBmih.biWidth; j++) {
dwColor = *pdwBits++;
b = (BYTE) ((dwColor & bmask) >> bright);
g = (BYTE) ((dwColor & gmask) >> gright);
r = (BYTE) ((dwColor & rmask) >> rright);
AddColor (&m_pTree, r, g, b, m_nColorBits, 0, &m_nLeafCount,
m_pReducibleNodes);
while (m_nLeafCount > m_nMaxColors)
ReduceTree (m_nColorBits, &m_nLeafCount, m_pReducibleNodes);
}
pdwBits = (DWORD*) (((BYTE*) pdwBits) + nPad);
}
break;
default: // Unrecognized color format
return FALSE;
}
return TRUE;
}
int CQuantizer::GetLeftShiftCount (DWORD dwVal)
{
int nCount = 0;
for (int i=0; i<sizeof (DWORD) * 8; i++) {
if (dwVal & 1)
nCount++;
dwVal >>= 1;
}
return (8 - nCount);
}
int CQuantizer::GetRightShiftCount (DWORD dwVal)
{
for (int i=0; i<sizeof (DWORD) * 8; i++) {
if (dwVal & 1)
return i;
dwVal >>= 1;
}
return -1;
}
void CQuantizer::AddColor (NODE** ppNode, BYTE r, BYTE g, BYTE b,
UINT nColorBits, UINT nLevel, UINT* pLeafCount, NODE** pReducibleNodes)
{
static BYTE mask[8] = { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };
//
// If the node doesn't exist, create it.
//
if (*ppNode == NULL)
*ppNode = CreateNode (nLevel, nColorBits, pLeafCount,
pReducibleNodes);
//
// Update color information if it's a leaf node.
//
if ((*ppNode)->bIsLeaf) {
(*ppNode)->nPixelCount++;
(*ppNode)->nRedSum += r;
(*ppNode)->nGreenSum += g;
(*ppNode)->nBlueSum += b;
}
//
// Recurse a level deeper if the node is not a leaf.
//
else {
int shift = 7 - nLevel;
int nIndex = (((r & mask[nLevel]) >> shift) << 2) |
(((g & mask[nLevel]) >> shift) << 1) |
((b & mask[nLevel]) >> shift);
AddColor (&((*ppNode)->pChild[nIndex]), r, g, b, nColorBits,
nLevel + 1, pLeafCount, pReducibleNodes);
}
}
NODE* CQuantizer::CreateNode (UINT nLevel, UINT nColorBits, UINT* pLeafCount,
NODE** pReducibleNodes)
{
NODE* pNode;
if ((pNode = (NODE*) HeapAlloc (GetProcessHeap (), HEAP_ZERO_MEMORY,
sizeof (NODE))) == NULL)
return NULL;
pNode->bIsLeaf = (nLevel == nColorBits) ? TRUE : FALSE;
if (pNode->bIsLeaf)
(*pLeafCount)++;
else {
pNode->pNext = pReducibleNodes[nLevel];
pReducibleNodes[nLevel] = pNode;
}
return pNode;
}
void CQuantizer::ReduceTree (UINT nColorBits, UINT* pLeafCount,
NODE** pReducibleNodes)
{
//
// Find the deepest level containing at least one reducible node.
//
for (int i=nColorBits - 1; (i>0) && (pReducibleNodes[i] == NULL); i--);
//
// Reduce the node most recently added to the list at level i.
//
NODE* pNode = pReducibleNodes[i];
pReducibleNodes[i] = pNode->pNext;
UINT nRedSum = 0;
UINT nGreenSum = 0;
UINT nBlueSum = 0;
UINT nChildren = 0;
for (i=0; i<8; i++) {
if (pNode->pChild[i] != NULL) {
nRedSum += pNode->pChild[i]->nRedSum;
nGreenSum += pNode->pChild[i]->nGreenSum;
nBlueSum += pNode->pChild[i]->nBlueSum;
pNode->nPixelCount += pNode->pChild[i]->nPixelCount;
HeapFree (GetProcessHeap (), 0, pNode->pChild[i]);
pNode->pChild[i] = NULL;
nChildren++;
}
}
pNode->bIsLeaf = TRUE;
pNode->nRedSum = nRedSum;
pNode->nGreenSum = nGreenSum;
pNode->nBlueSum = nBlueSum;
*pLeafCount -= (nChildren - 1);
}
void CQuantizer::DeleteTree (NODE** ppNode)
{
for (int i=0; i<8; i++) {
if ((*ppNode)->pChild[i] != NULL)
DeleteTree (&((*ppNode)->pChild[i]));
}
HeapFree (GetProcessHeap (), 0, *ppNode);
*ppNode = NULL;
}
void CQuantizer::GetPaletteColors (NODE* pTree, RGBQUAD* prgb, UINT* pIndex)
{
if (pTree->bIsLeaf) {
prgb[*pIndex].rgbRed =
(BYTE) ((pTree->nRedSum) / (pTree->nPixelCount));
prgb[*pIndex].rgbGreen =
(BYTE) ((pTree->nGreenSum) / (pTree->nPixelCount));
prgb[*pIndex].rgbBlue =
(BYTE) ((pTree->nBlueSum) / (pTree->nPixelCount));
prgb[*pIndex].rgbReserved = 0;
(*pIndex)++;
}
else {
for (int i=0; i<8; i++) {
if (pTree->pChild[i] != NULL)
GetPaletteColors (pTree->pChild[i], prgb, pIndex);
}
}
}
UINT CQuantizer::GetColorCount ()
{
return m_nLeafCount;
}
void CQuantizer::GetColorTable (RGBQUAD* prgb)
{
UINT nIndex = 0;
GetPaletteColors (m_pTree, prgb, &nIndex);
}