// split image into 8-bit channels
// N.B.: when casting the transformation result to unsigned shorts
// (8-bit channel), major rounding errors will occur.
// As a result, the merging operation might
// produce negative values or values > 1, which are truncated subsequently.
// When accurate X, Y and Z channels are required, prefer float channels!
bool splitImageToxyY::apply(const image& img,
channel8& c1,
channel8& c2,
channel8& c3) const {
point p; // coordinates
rgbPixel pix; // single Pixel Element in RGB-values...
float Y; // channels
float X, XYZ; // help variables
// make the channels size of source image...
c1.resize(img.rows(),img.columns(),0,false,false);
c2.resize(img.rows(),img.columns(),0,false,false);
c3.resize(img.rows(),img.columns(),0,false,false);
for (p.y=0;p.y<img.rows();p.y++)
for (p.x=0;p.x<img.columns();p.x++) {
// take pixel at position p
pix = img.at(p);
// see Gonzales & Woods for explanation of magic numbers
X = (((float)(pix.getRed())) *0.412453f +
((float)(pix.getGreen())) *0.357580f +
((float)(pix.getBlue())) *0.180423f)/255.0f; // x
Y = (((float)(pix.getRed())) *0.212671f +
((float)(pix.getGreen())) *0.715160f +
((float)(pix.getBlue())) *0.072169f)/255.0f; // y
XYZ = (((float)(pix.getRed())) *0.644458f +
((float)(pix.getGreen())) *1.191933f +
((float)(pix.getBlue())) *1.202819f)/255.0f; // Y
if (XYZ>0.0f) {
c1.at(p) = (ubyte)(X/XYZ*255.0f); // x
c2.at(p) = (ubyte)(Y/XYZ*255.0f); // y
}
else {
c1.at(p) = 0; // x
c2.at(p) = 0; // y
}
c3.at(p) = (ubyte)(Y*255.0f); // Y
} // loop
return true;
}
// On copy apply for type channel8!
bool harrisCorners::apply(const channel8& src,channel8& dest) const {
pointList pts;
if (apply(src,pts)) {
const parameters& par = getParameters();
pointList::iterator it;
dest.resize(src.size(),par.noCornerValue,false,true);
for (it=pts.begin();it!=pts.end();++it) {
dest.at(*it)=par.cornerValue;
}
return true;
}
return false;
};
// Quantization takes place here!
bool medianCut::performQuantization(const image& src,
image& dest,
channel8& mask,
palette &thePalette) const {
// parameters and const variables
const parameters& param = getParameters();
const int imageRows=src.rows(); // number of rows in src
const int imageCols=src.columns(); // number of columns in src
// resize destination containers
dest.resize(imageRows,imageCols,rgbPixel(),false,false);
mask.resize(imageRows,imageCols,ubyte(),false,false);
// Variables
int row,col; // row, column counters
int r,g,b; // red,green,blue
ivector iVec(3); // int-vector
std::list<boxInfo> theLeaves; // list of leaves (tree without root
// and nodes)
std::list<boxInfo>::iterator splitPos; // position to split
std::list<boxInfo>::iterator iter; // iterator for theLeaves
// create histogram with desired pre-quantization dimensions from src
histogram theHist(3,param.preQuant);
const float factor = param.preQuant/256.0f;
for (row = 0 ; row < imageRows ; row++) {
for (col = 0 ; col < imageCols ; col++) {
r = static_cast<int>(src.at( row,col ).getRed() * factor);
g = static_cast<int>(src.at( row,col ).getGreen() * factor);
b = static_cast<int>(src.at( row,col ).getBlue() * factor);
// insert point with quantized color
dest.at(row,col).set((r*256+128)/param.preQuant,
(g*256+128)/param.preQuant,
(b*256+128)/param.preQuant,0);
iVec[0] = r;
iVec[1] = g;
iVec[2] = b;
theHist.put(iVec);
}
}
// initialization of first box of list (the whole histogram)
boxInfo theBox(rgbPixel(0,0,0),
rgbPixel(param.preQuant-1,
param.preQuant-1,
param.preQuant-1));
computeBoxInfo(theHist,theBox);
// return, if desired number of colors smaller than colors in
// pre-quantized image
if (theBox.colors < param.numberOfColors) {
thePalette.resize(theBox.colors,rgbPixel(),false,false);
// prepare palette
int i = 0;
for (r=0;r<param.preQuant;++r) {
for (g=0;g<param.preQuant;++g) {
for (b=0;b<param.preQuant;++b) {
iVec[0] = r;
iVec[1] = g;
iVec[2] = b;
if (theHist.at(iVec) > 0) {
thePalette.at(i).set((r*256+128)/param.preQuant,
(g*256+128)/param.preQuant,
(b*256+128)/param.preQuant);
}
}
}
}
// use the palette to generate the corresponding channel
usePalette colorizer;
colorizer.apply(dest,thePalette,mask);
return true;
}
// Push first box into List
theLeaves.push_back(theBox);
// MAIN LOOP (do this until you have enough leaves (count), or no
// splittable boxes (entries))
int count, entries=1; // auxiliary variables for the main loop
for (count=1; (count<param.numberOfColors) && (entries!=0); count++) {
// find box with largest number of entries from list
entries = 0;
for (iter = theLeaves.begin() ; iter != theLeaves.end() ; iter++) {
if ( (*iter).colorFrequency > entries ) {
// Avoid choosing single colors, i.e. unsplittable boxes
if ( ((*iter).max.getRed() > (*iter).min.getRed()) ||
((*iter).max.getGreen() > (*iter).min.getGreen()) ||
((*iter).max.getBlue() > (*iter).min.getBlue()) ) {
entries = (*iter).colorFrequency;
splitPos = iter;
}
}
}
// A splittable box was found.
// The iterator "splitPos" indicates its position in the List
if (entries >0) {
// Determine next axis to split (largest variance) and box dimensions
int splitAxis; // split axis indicator
if ( ((*splitPos).var[0] >= (*splitPos).var[1]) &&
((*splitPos).var[0] >= (*splitPos).var[2]) ) {
splitAxis = 0; // red axis
}
else if ( (*splitPos).var[1] >= (*splitPos).var[2] ) {
splitAxis = 1; // green axis
}
else {
splitAxis = 2; // blue axis
}
int rMax = ((*splitPos).max.getRed());
int rMin = ((*splitPos).min.getRed());
int gMax = ((*splitPos).max.getGreen());
int gMin = ((*splitPos).min.getGreen());
int bMax = ((*splitPos).max.getBlue());
int bMin = ((*splitPos).min.getBlue());
// pass through box along the axis to split
bool found; // becomes true when split plane is found
int nrOfCols=0; // counter: number of colors of box
int prevNrOfCols=0; // forerunner of nrOfCols
rgbPixel lower1; // lower pixel from box 1
rgbPixel upper1; // upper pixel from box 1
rgbPixel lower2; // lower pixel from box 2
rgbPixel upper2; // upper pixel from box 2
switch (splitAxis) {
case 0: // red axis
nrOfCols = 0;
for (r = rMin , found = false ; (!found) && (r<=rMax) ; r++) {
prevNrOfCols = nrOfCols;
for (g = gMin ; g <= gMax ; g++) {
for (b=bMin;b<=bMax;b++) {
iVec[0] = r;
iVec[1] = g;
iVec[2] = b;
if (theHist.at(iVec) > 0.0) {
nrOfCols += static_cast<long int>(theHist.at(iVec));
}
}
}
if ( nrOfCols >= (*splitPos).colorFrequency/2 ) {
found=true;
}
}
if (fabs(prevNrOfCols -
static_cast<float>((*splitPos).colorFrequency)/2) <
fabs(nrOfCols -
static_cast<float>((*splitPos).colorFrequency)/2)) {
r--;
nrOfCols = prevNrOfCols;
}
// first box
lower1.setRed(rMin); lower1.setGreen(gMin); lower1.setBlue(bMin);
upper1.setRed(r-1); upper1.setGreen(gMax); upper1.setBlue(bMax);
// second box
lower2.setRed(r); lower2.setGreen(gMin); lower2.setBlue(bMin);
upper2.setRed(rMax); upper2.setGreen(gMax); upper2.setBlue(bMax);
break;
case 1: // g axis
nrOfCols = 0;
for (g = gMin , found = false ; (!found) && (g<=gMax) ; g++) {
prevNrOfCols = nrOfCols;
for (r = rMin ; r <= rMax ; r++) {
for (b = bMin ; b <= bMax ; b++) {
iVec[0] = r;
iVec[1] = g;
iVec[2] = b;
if (theHist.at(iVec) > 0.0) {
nrOfCols += static_cast<long int>(theHist.at(iVec));
}
}
}
if ( nrOfCols >= (*splitPos).colorFrequency/2 ) {
found=true;
}
}
if (fabs(prevNrOfCols -
static_cast<float>((*splitPos).colorFrequency)/2) <
fabs(nrOfCols -
static_cast<float>((*splitPos).colorFrequency)/2)) {
g--;
nrOfCols = prevNrOfCols;
}
// first box
lower1.setRed(rMin); lower1.setGreen(gMin); lower1.setBlue(bMin);
upper1.setRed(rMax); upper1.setGreen(g-1); upper1.setBlue(bMax);
// second box
lower2.setRed(rMin); lower2.setGreen(g); lower2.setBlue(bMin);
upper2.setRed(rMax); upper2.setGreen(gMax); upper2.setBlue(bMax);
break;
case 2: // b axis
nrOfCols = 0;
for (b = bMin , found = false ; (!found) && (b<=bMax) ; b++) {
prevNrOfCols = nrOfCols;
for (r = rMin ; r <= rMax ; r++) {
for (g = gMin ; g <= gMax ; g++) {
iVec[0] = r;
iVec[1] = g;
iVec[2] = b;
if (theHist.at(iVec) > 0.0) {
nrOfCols += static_cast<long int>(theHist.at(iVec));
}
}
}
if ( nrOfCols >= (*splitPos).colorFrequency/2 ) {
found=true;
}
}
if (fabs(prevNrOfCols -
static_cast<float>((*splitPos).colorFrequency)/2) <
fabs(nrOfCols -
static_cast<float>((*splitPos).colorFrequency)/2)) {
b--;
nrOfCols = prevNrOfCols;
}
// first box
lower1.setRed(rMin); lower1.setGreen(gMin); lower1.setBlue(bMin);
upper1.setRed(rMax); upper1.setGreen(gMax); upper1.setBlue(b-1);
// second box
lower2.setRed(rMin); lower2.setGreen(gMin); lower2.setBlue(b);
upper2.setRed(rMax); upper2.setGreen(gMax); upper2.setBlue(bMax);
break;
default:
break;
} // end of switch
// compute box info of new boxes and
// append both at the end of list
theBox.min = lower1;
theBox.max = upper1;
computeBoxInfo(theHist,theBox);
theLeaves.push_back(theBox);
theBox.min = lower2;
theBox.max = upper2;
computeBoxInfo(theHist,theBox);
theLeaves.push_back(theBox);
// delete splited box from list
theLeaves.erase(splitPos);
}
} // end of for (MAIN LOOP)
// compute block histogram and respective color palette
thePalette.resize(theLeaves.size());
int i;
for (iter = theLeaves.begin() , i=0 ;
iter != theLeaves.end() ;
iter++ , i++) {
// misuse histogram as a look-up-table
for (r = (*iter).min.getRed(); r <= (*iter).max.getRed(); r++) {
for (g = (*iter).min.getGreen(); g <= (*iter).max.getGreen(); g++) {
for (b = (*iter).min.getBlue(); b <= (*iter).max.getBlue(); b++) {
iVec[0] = r;
iVec[1] = g;
iVec[2] = b;
theHist.at(iVec) = i; // insert palette-index (refers to
// color in palette)
}
}
}
// create palette
r = (static_cast<int>((*iter).mean[0]*factor)*256+128)/param.preQuant;
g = (static_cast<int>((*iter).mean[1]*factor)*256+128)/param.preQuant;
b = (static_cast<int>((*iter).mean[2]*factor)*256+128)/param.preQuant;
thePalette[i].set(r,g,b,0); // insert color
}
// create new image with palette and theHist
dest.resize(imageRows,imageCols);
mask.resize(imageRows,imageCols,0,false,true);
// <= 256 colors? then also fill the mask
if (thePalette.size() <= 256) {
for (row = 0 ; row < imageRows ; row++) {
for (col = 0 ; col < imageCols ; col++) {
iVec[0] = static_cast<int>(src.at( row,col ).getRed() * factor);
iVec[1] = static_cast<int>(src.at( row,col ).getGreen() * factor);
iVec[2] = static_cast<int>(src.at( row,col ).getBlue() * factor);
i = static_cast<int>(theHist.at( iVec ));
dest.at(row,col) = thePalette[i];// insert point with quantized color
mask.at(row,col) = i; // insert palette index of quantized color
}
}
}
else {
for (row = 0 ; row < imageRows ; row++) {
for (col = 0 ; col < imageCols ; col++) {
iVec[0] = static_cast<int>(src.at( row,col ).getRed() * factor);
iVec[1] = static_cast<int>(src.at( row,col ).getGreen() * factor);
iVec[2] = static_cast<int>(src.at( row,col ).getBlue() * factor);
i = static_cast<int>(theHist.at( iVec ));
r = thePalette[i].getRed();
g = thePalette[i].getGreen();
b = thePalette[i].getBlue();
dest.at(row,col).set(r,g,b,0); // insert point with quantized color
}
}
}
return true;
}
