/**
* Simple octree color quantization: Similar to http://rosettacode.org/wiki/Color_quantization#C
*/
void octreeColorQuantize(const RGBAImage& image, size_t max_colors,
std::vector<RGBAPixel>& colors, Octree** octree) {
assert(max_colors > 0);
// have an octree with the colors as leaves
Octree* internal_octree = new Octree();
// and a priority queue of leaves to be processed
// the order of leaves is very important, see NodeComparator
std::priority_queue<Octree*, std::vector<Octree*>, NodeComparator> queue;
// insert the colors into the octree
for (int x = 0; x < image.getWidth(); x++) {
for (int y = 0; y < image.getHeight(); y++) {
RGBAPixel color = image.pixel(x, y);
Octree* node = Octree::findOrCreateNode(internal_octree, color);
node->setColor(color);
// add the leaf only once to the queue
if (node->getCount() == 1)
queue.push(node);
}
}
// now: reduce the leaves until we have less colors than maximum
while (queue.size() > max_colors) {
Octree* node = queue.top();
assert(node->isLeaf());
queue.pop();
// add the color value of the leaf to the parent
node->reduceToParent();
Octree* parent = node->getParent();
// delete the leaf (leaf is automatically removed from parent in reduceToParent())
delete node;
// add parent to queue if it is a leaf now
if (parent->isLeaf())
queue.push(parent);
}
// gather the quantized colors
while (queue.size()) {
Octree* node = queue.top();
assert(node->isLeaf());
node->setColorID(colors.size());
colors.push_back(node->getColor());
queue.pop();
}
if (octree != nullptr)
*octree = internal_octree;
else
delete internal_octree;
}
void testOctreeWithImage(const RGBAImage& image) {
std::set<RGBAPixel> colors;
int r = 0, g = 0, b = 0, count = 0;
Octree octree;
// insert all pixels into an octree
for (int x = 0; x < image.getWidth(); x++) {
for (int y = 0; y < image.getHeight(); y++) {
RGBAPixel color = image.getPixel(x, y);
colors.insert(color);
r += rgba_red(color);
g += rgba_green(color);
b += rgba_blue(color);
count++;
Octree::findOrCreateNode(&octree, color)->setColor(color);
}
}
// make sure that all colors are inserted correctly
BOOST_CHECK(octree.isRoot() && !octree.isLeaf());
BOOST_CHECK(!octree.hasColor());
// reduce all colors up to the root of the tree
// the color should be the overall average color
traverseReduceOctree(&octree);
BOOST_CHECK(octree.hasColor());
RGBAPixel average1 = octree.getColor();
RGBAPixel average2 = rgba(r / count, g / count, b / count, 255);
BOOST_CHECK_EQUAL(average1, average2);
BOOST_TEST_MESSAGE("Overall colors: " << colors.size());
BOOST_TEST_MESSAGE("Pixels per color: " << (double) (image.getWidth() * image.getHeight()) / colors.size());
BOOST_TEST_MESSAGE("Average color: " << (int) rgba_red(average1) << ","
<< (int) rgba_green(average1) << "," << (int) rgba_blue(average1));
}