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Initial implementation of Floyd-Steinberg dithering

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This commit is contained in:
Kovid Goyal 2016-05-08 21:15:50 +05:30
parent d1be20bae3
commit e163470978
1 changed files with 91 additions and 16 deletions
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107
src/calibre/utils/imageops/quantize.cpp
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@ -18,6 +18,7 @@
typedef unsigned __int64 uint64_t;
typedef __int64 int64_t;
typedef unsigned __int32 uint32_t;
#define UINT64_MAX _UI64_MAX
#ifndef log2
static inline double log2(double x) { return log(x) / log((double)2) ; }
#endif
@ -32,8 +33,11 @@ static const unsigned char BIT_MASK[8] = { 1 << 7, 1 << 6, 1 << 5, 1 << 4, 1 <<
static inline size_t get_index(const uint32_t r, const uint32_t g, const uint32_t b, const size_t level) {
return ((((r & BIT_MASK[level]) >> (7 - level)) << 2) | (((g & BIT_MASK[level]) >> (7 - level)) << 1) | ((b & BIT_MASK[level]) >> (7 - level)));
}
template <typename T> static inline T euclidean_distance(T r1, T g1, T b1, T r2, T g2, T b2) {
return r1 * r1 + r2 * r2 + g1 * g1 + g2 * g2 + b1 * b1 + b2 * b2 - 2 * (r1 * r2 + g1 * g2 + b1 * b2);
}
template <class T> class Pool {
template <class T> class Pool { // {{{
private:
QVector<T> nodes;
T *first_available;
@ -62,7 +66,7 @@ public:
node->next_available_in_pool = this->first_available;
this->first_available = node;
}
};
}; // }}}
class Node {
friend class Pool<Node>;
@ -73,6 +77,9 @@ private:
uint64_t red_sum;
uint64_t green_sum;
uint64_t blue_sum;
unsigned char red_avg;
unsigned char green_avg;
unsigned char blue_avg;
Node* next_reducible_node;
Node *next_available_in_pool;
Node* children[MAX_DEPTH];
@ -82,7 +89,7 @@ public:
// Disable the new behavior warning caused by children() below
#pragma warning( push )
#pragma warning (disable: 4351)
Node() : is_leaf(false), index(0), pixel_count(0), red_sum(0), green_sum(0), blue_sum(0), next_reducible_node(NULL), next_available_in_pool(NULL), children() {}
Node() : is_leaf(false), index(0), pixel_count(0), red_sum(0), green_sum(0), blue_sum(0), red_avg(0), green_avg(0), blue_avg(0), next_reducible_node(NULL), next_available_in_pool(NULL), children() {}
#pragma warning ( pop )
#endif
@ -152,15 +159,29 @@ public:
node->is_leaf = true; *leaf_count += 1;
}
void set_palette_colors(QRgb *color_table, unsigned char *index) {
void set_palette_colors(QRgb *color_table, unsigned char *index, bool compute_parent_averages) {
int i;
Node *child;
if (this->is_leaf) {
#define AVG_COLOR(x) ((int) ((double)this->x / (double)this->pixel_count))
color_table[*index] = qRgb(AVG_COLOR(red_sum), AVG_COLOR(green_sum), AVG_COLOR(blue_sum));
#define AVG_COLOR(x) ((unsigned char) ((double)this->x / (double)this->pixel_count))
this->red_avg = AVG_COLOR(red_sum); this->green_avg = AVG_COLOR(green_sum); this->blue_avg = AVG_COLOR(blue_sum);
color_table[*index] = qRgb(this->red_avg, this->green_avg, this->blue_avg);
this->index = (*index)++;
} else {
for (i = 0; i < MAX_DEPTH; i++) {
if (this->children[i] != NULL) this->children[i]->set_palette_colors(color_table, index);
child = this->children[i];
if (child != NULL) {
child->set_palette_colors(color_table, index, compute_parent_averages);
if (compute_parent_averages) {
this->pixel_count += child->pixel_count;
this->red_sum += child->pixel_count * child->red_avg;
this->green_sum += child->pixel_count * child->green_avg;
this->blue_sum += child->pixel_count * child->blue_avg;
}
}
}
if (compute_parent_averages) {
this->red_avg = AVG_COLOR(red_sum); this->green_avg = AVG_COLOR(green_sum); this->blue_avg = AVG_COLOR(blue_sum);
}
}
}
@ -171,8 +192,59 @@ public:
if (this->children[index] == NULL) throw std::out_of_range("Something bad happened: could not follow tree for color");
return this->children[index]->index_for_color(r, g, b, level + 1);
}
unsigned char index_for_nearest_color(const uint32_t r, const uint32_t g, const uint32_t b, const size_t level) {
if (this->is_leaf) return this->index;
size_t index = get_index(r, g, b, level);
if (this->children[index] == NULL) {
uint64_t min_distance = UINT64_MAX, distance;
for(size_t i = 0; i < MAX_DEPTH; i++) {
Node *child = this->children[i];
if (child != NULL) {
distance = euclidean_distance<uint64_t>(r, g, b, child->red_avg, child->green_avg, child->blue_avg);
if (distance < min_distance) { min_distance = distance; index = i; }
}
}
}
return this->children[index]->index_for_nearest_color(r, g, b, level + 1);
}
};
static inline void propagate_error(QRgb* line, int c, unsigned char mult, int red_error, int green_error, int blue_error) {
QRgb pixel = *(line + c);
#define PROPERR(w, e) MAX(0, MIN((w(pixel) + ((mult * e) >> 4)), 255))
*(line + c) = qRgb(PROPERR(qRed, red_error), PROPERR(qGreen, green_error), PROPERR(qBlue, blue_error));
}
static void dither_image(QImage &img, QImage &ans, QVector<QRgb> &color_table, Node &root) {
QRgb *mline = NULL, *sline = NULL, pixel = 0, new_pixel = 0;
unsigned char *bits = NULL, index = 0;
int red_error = 0, green_error = 0, blue_error = 0, iheight = img.height(), iwidth = img.width(), r = 0, c = 0;
for (r = 0; r < iheight; r++) {
mline = reinterpret_cast<QRgb*>(img.scanLine(r));
sline = r + 1 < iheight ? reinterpret_cast<QRgb*>(img.scanLine(r+1)) : NULL;
bits = ans.scanLine(r);
for (c = 0; c < iwidth; c++) {
pixel = *(mline + c);
index = root.index_for_nearest_color(qRed(pixel), qGreen(pixel), qBlue(pixel), 0);
*(bits + c) = index;
new_pixel = color_table[index];
red_error = qRed(pixel) - qRed(new_pixel);
green_error = qGreen(pixel) - qGreen(new_pixel);
blue_error = qBlue(pixel) - qBlue(new_pixel);
if (c + 1 < iwidth) {
propagate_error(mline, c + 1, 7, red_error, green_error, blue_error);
if (sline != NULL) propagate_error(sline, c + 1, 1, red_error, green_error, blue_error);
}
if (sline != NULL) {
propagate_error(sline, c, 5, red_error, green_error, blue_error);
if (c > 1) propagate_error(sline, c - 1, 3, red_error, green_error, blue_error);
}
}
}
}
QImage quantize(const QImage &image, unsigned int maximum_colors, bool dither) {
ScopedGILRelease PyGILRelease;
@ -180,12 +252,11 @@ QImage quantize(const QImage &image, unsigned int maximum_colors, bool dither) {
int iwidth = image.width(), iheight = image.height(), r, c;
QImage img(image), ans(iwidth, iheight, QImage::Format_Indexed8);
unsigned int leaf_count = 0;
unsigned char index = 0;
unsigned char index = 0, *bits;
Node* reducible_nodes[MAX_DEPTH + 1] = {0};
Node root = Node();
QVector<QRgb> color_table = QVector<QRgb>(MAX_COLORS);
const QRgb* line = NULL;
unsigned char *bits = NULL;
root.check_compiler();
@ -216,15 +287,19 @@ QImage quantize(const QImage &image, unsigned int maximum_colors, bool dither) {
if (leaf_count > maximum_colors) throw std::out_of_range("Leaf count > max colors, something bad happened");
color_table.resize(leaf_count);
root.set_palette_colors(color_table.data(), &index);
root.set_palette_colors(color_table.data(), &index, dither);
ans.setColorTable(color_table);
for (r = 0; r < iheight; r++) {
line = reinterpret_cast<const QRgb*>(img.constScanLine(r));
bits = ans.scanLine(r);
for (c = 0; c < iwidth; c++) {
const QRgb pixel = *(line + c);
*(bits + c) = root.index_for_color(qRed(pixel), qGreen(pixel), qBlue(pixel), 0);
if (dither) {
dither_image(img, ans, color_table, root);
} else {
for (r = 0; r < iheight; r++) {
line = reinterpret_cast<const QRgb*>(img.constScanLine(r));
bits = ans.scanLine(r);
for (c = 0; c < iwidth; c++) {
const QRgb pixel = *(line + c);
*(bits + c) = root.index_for_color(qRed(pixel), qGreen(pixel), qBlue(pixel), 0);
}
}
}