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// Fast and accurate bitmap scaling. Original code by Eran Yariv and Jake Montgomery,
// posted on codeguru.com.
#ifndef _TwoPassScale_h_
#define _TwoPassScale_h_
#include "ContribDefs.h"
#include "../base/Exception.h"
#include <math.h>
#include <algorithm>
#include <cstring>
namespace avg {
typedef struct
{
int *Weights; // Normalized weights of neighboring pixels
int Left,Right; // Bounds of source pixels window
} ContributionType; // Contirbution information for a single pixel
typedef struct
{
ContributionType *ContribRow; // Row (or column) of contribution weights
int WindowSize, // Filter window size (of affecting source pixels)
LineLength; // Length of line (no. or rows / cols)
} LineContribType; // Contribution information for an entire line (row or column)
class CDataA_UBYTE
{
public:
typedef unsigned char PixelClass;
class _Accumulator {
public:
_Accumulator ()
{
val = 0;
};
void Accumulate (int Weight, PixelClass &value)
{
val += (Weight * value);
};
void Store (PixelClass* value)
{
*value = (unsigned char) ((val + 128)/256);
};
int val;
};
};
class CDataRGB_UBYTE
{
public:
typedef unsigned char PixelClass[3];
class _Accumulator {
public:
_Accumulator ()
{
val [0] = val [1] = val [2] = 0;
};
void Accumulate (int Weight, PixelClass &value)
{
val [0] += (Weight * value [0]);
val [1] += (Weight * value [1]);
val [2] += (Weight * value [2]);
};
void Store (PixelClass* value)
{
(*value) [0] = (unsigned char) ((val [0] + 128)/256);
(*value) [1] = (unsigned char) ((val [1] + 128)/256);
(*value) [2] = (unsigned char) ((val [2] + 128)/256);
};
int val [3];
};
};
class CDataRGBA_UBYTE {
public:
typedef unsigned char PixelClass[4];
class _Accumulator {
public:
_Accumulator ()
{
val [0] = val [1] = val [2] = val [3] = 0;
};
void Accumulate (int dWeight, PixelClass &value)
{
val [0] += (dWeight * (value [0]));
val [1] += (dWeight * (value [1]));
val [2] += (dWeight * (value [2]));
val [3] += (dWeight * (value [3]));
};
void Store (PixelClass* value)
{
(*value) [0] = (unsigned char) ((val [0] + 128)/256);
(*value) [1] = (unsigned char) ((val [1] + 128)/256);
(*value) [2] = (unsigned char) ((val [2] + 128)/256);
(*value) [3] = (unsigned char) ((val [3] + 128)/256);
};
int val [4];
};
};
template <class DataClass>
class TwoPassScale
{
public:
typedef typename DataClass::PixelClass PixelClass;
TwoPassScale (const ContribDef& contribDef)
: m_ContribDef (contribDef)
{};
virtual ~TwoPassScale() {};
void Scale(PixelClass * pSrcData, const IntPoint& srcSize, int srcStride,
PixelClass *pDstData, const IntPoint& dstSize, int dstStride);
private:
LineContribType *AllocContributions (unsigned uLineLength,
unsigned uWindowSize);
void FreeContributions (LineContribType * p);
LineContribType *CalcContributions (unsigned uLineSize,
unsigned uSrcSize);
void ScaleRow(PixelClass *pSrc, int uSrcWidth, PixelClass *pDest, int uResWidth,
LineContribType *pContrib);
void HorizScale(PixelClass * pSrcData, const IntPoint& srcSize, int srcStride,
PixelClass *pDestData, const IntPoint& destSize, int destStride);
void VertScale(PixelClass *pSrcData, const IntPoint& srcSize, int srcStride,
PixelClass *pDestData, const IntPoint& destSize, int destStride);
const ContribDef& m_ContribDef;
};
template <class DataClass>
LineContribType *
TwoPassScale<DataClass>::AllocContributions (unsigned uLineLength, unsigned uWindowSize)
{
LineContribType *res = new LineContribType;
// Init structure header
res->WindowSize = uWindowSize;
res->LineLength = uLineLength;
// Allocate list of contributions
res->ContribRow = new ContributionType[uLineLength];
for (unsigned u = 0 ; u < uLineLength ; u++)
{
// Allocate contributions for every pixel
res->ContribRow[u].Weights = new int[uWindowSize];
}
return res;
}
template <class DataClass>
void
TwoPassScale<DataClass>::FreeContributions (LineContribType * p)
{
for (int u = 0; u < p->LineLength; u++)
{
// Free contribs for every pixel
delete [] p->ContribRow[u].Weights;
}
delete [] p->ContribRow; // Free list of pixels contribs
delete p; // Free contribs header
}
template <class DataClass>
LineContribType *
TwoPassScale<DataClass>::CalcContributions(unsigned uLineSize, unsigned uSrcSize)
{
float dScale = float(uLineSize)/uSrcSize;
float dWidth;
float dFScale = 1.0;
float dFilterWidth = m_ContribDef.GetWidth();
if (dScale < 1.0) {
// Minification
dWidth = dFilterWidth / dScale;
dFScale = dScale;
} else {
// Magnification
dWidth= dFilterWidth;
}
// Window size is the number of sampled pixels
int iWindowSize = 2 * (int)ceil(dWidth) + 1;
// Allocate a new line contributions strucutre
LineContribType *res = AllocContributions (uLineSize, iWindowSize);
for (unsigned u = 0; u < uLineSize; u++) {
// Scan through line of contributions
float dCenter = (u+0.5f)/dScale-0.5f; // Reverse mapping
// Find the significant edge points that affect the pixel
int iLeft = std::max (0, (int)floor (dCenter - dWidth));
int iRight = std::min ((int)ceil (dCenter + dWidth), int(uSrcSize) - 1);
// Cut edge points to fit in filter window in case of spill-off
if (iRight - iLeft + 1 > iWindowSize) {
if (iLeft < (int(uSrcSize) - 1 / 2)) {
iLeft++;
} else {
iRight--;
}
}
res->ContribRow[u].Left = iLeft;
res->ContribRow[u].Right = iRight;
int dTotalWeight = 0; // Zero sum of weights
for (int iSrc = iLeft; iSrc <= iRight; iSrc++) {
// Calculate weights
int CurWeight = int (dFScale * (m_ContribDef.Filter (dFScale *
(dCenter - (float)iSrc)))*256);
res->ContribRow[u].Weights[iSrc-iLeft] = CurWeight;
dTotalWeight += CurWeight;
}
AVG_ASSERT(dTotalWeight >= 0); // An error in the filter function can cause this
int UsedWeight = 0;
if (dTotalWeight > 0) {
// Normalize weight of neighbouring points
for (int iSrc = iLeft; iSrc < iRight; iSrc++) {
// Normalize point
int CurWeight = (res->ContribRow[u].Weights[iSrc-iLeft]*256)/dTotalWeight;
res->ContribRow[u].Weights[iSrc-iLeft] = CurWeight;
UsedWeight += CurWeight;
}
// The last point gets everything that's left over so the sum is
// always correct.
res->ContribRow[u].Weights[iRight-iLeft] = 256 - UsedWeight;
}
}
return res;
}
template <class DataClass>
void
TwoPassScale<DataClass>::ScaleRow(PixelClass *pSrc, int uSrcWidth,
PixelClass *pDest, int uResWidth, LineContribType *pContrib)
{
PixelClass * pDestPixel = pDest;
for (int x = 0; x < uResWidth; x++) {
typename DataClass::_Accumulator a;
int iLeft = pContrib->ContribRow[x].Left; // Retrieve left boundries
int iRight = pContrib->ContribRow[x].Right; // Retrieve right boundries
int * Weights = pContrib->ContribRow[x].Weights;
for (int i = iLeft; i <= iRight; i++) {
// Scan between boundries
// Accumulate weighted effect of each neighboring pixel
a.Accumulate(Weights[i-iLeft], pSrc[i]);
}
a.Store(pDestPixel);
pDestPixel++;
}
}
template <class DataClass>
void TwoPassScale<DataClass>::HorizScale(PixelClass * pSrcData, const IntPoint& srcSize,
int srcStride, PixelClass *pDestData, const IntPoint& destSize, int destStride)
{
PixelClass * pSrc = pSrcData;
PixelClass * pDest = pDestData;
if (srcSize.x == destSize.x) {
// No scaling required, just copy
for (int y = 0; y < destSize.y; y++) {
memcpy(pDest, pSrc, sizeof (PixelClass) * srcSize.x);
pSrc = (PixelClass*)((char*)(pSrc)+srcStride);
pDest = (PixelClass*)((char*)(pDest)+destStride);
}
} else {
LineContribType * pContrib = CalcContributions(destSize.x, srcSize.x);
for (int y = 0; y < destSize.y; y++) {
ScaleRow(pSrc, srcSize.x, pDest, destSize.x, pContrib);
pSrc = (PixelClass*)((char*)(pSrc)+srcStride);
pDest = (PixelClass*)((char*)(pDest)+destStride);
}
FreeContributions(pContrib); // Free contributions structure
}
}
template <class DataClass>
void TwoPassScale<DataClass>::VertScale(PixelClass *pSrcData, const IntPoint& srcSize,
int srcStride, PixelClass *pDestData, const IntPoint& destSize, int destStride)
{
PixelClass * pSrc = pSrcData;
PixelClass * pDest = pDestData;
if (srcSize.y == destSize.y) {
// No scaling required, just copy
for (int y = 0; y < destSize.y; y++) {
memcpy(pDest, pSrc, sizeof (PixelClass) * srcSize.x);
pSrc = (PixelClass*)((char*)(pSrc)+srcStride);
pDest = (PixelClass*)((char*)(pDest)+destStride);
}
} else {
LineContribType * pContrib = CalcContributions(destSize.y, srcSize.y);
for (int y = 0; y < destSize.y; y++) {
PixelClass * pDestPixel = pDest;
int * pWeights = pContrib->ContribRow[y].Weights;
int iLeft = pContrib->ContribRow[y].Left;
int iRight = pContrib->ContribRow[y].Right;
PixelClass* pSrcPixelBase = (PixelClass*)((char*)(pSrc)
+ size_t(iLeft)*srcStride);
for (int x = 0; x < destSize.x; x++) {
typename DataClass::_Accumulator a;
int * pWeight = pWeights;
PixelClass * pSrcPixel = pSrcPixelBase;
pSrcPixelBase++;
for (int i = iLeft; i <= iRight; i++) {
// Scan between boundries
// Accumulate weighted effect of each neighboring pixel
a.Accumulate(*pWeight, *pSrcPixel);
pWeight++;
pSrcPixel = (PixelClass*)((char*)(pSrcPixel)+srcStride);
}
a.Store(pDestPixel);
pDestPixel++;
}
pDest = (PixelClass*)((char*)(pDest)+destStride);
}
FreeContributions(pContrib); // Free contributions structure
}
}
template <class DataClass>
void TwoPassScale<DataClass>::Scale(PixelClass * pSrcData, const IntPoint& srcSize,
int srcStride, PixelClass *pDstData, const IntPoint& dstSize, int dstStride)
{
// Allocate temp image
PixelClass *pTempData = new PixelClass[srcSize.y*dstSize.x];
IntPoint tempSize(dstSize.x, srcSize.y);
int tempStride = dstSize.x*sizeof(PixelClass);
// Scale source image horizontally into temporary image
HorizScale(pSrcData, srcSize, srcStride,
pTempData, tempSize, tempStride);
// Scale temporary image vertically into result image
VertScale (pTempData, tempSize, tempStride,
pDstData, dstSize, dstStride);
delete [] pTempData;
}
}
#endif
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