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apply fix from Marcin for semitransparency of png256 - closes #477 and resolves discussion at #202

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This commit is contained in:
Dane Springmeyer 2010-01-05 15:54:25 +00:00
parent 9750e6cd24
commit b3711b07d1
2 changed files with 229 additions and 64 deletions
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27
include/mapnik/octree.hpp
View file

@ -105,6 +105,7 @@ namespace mapnik {
std::deque<node*> reducible_[InsertPolicy::MAX_LEVELS];
unsigned max_colors_;
unsigned colors_;
unsigned offset_;
unsigned leaf_level_;
bool has_alfa_;
@ -112,6 +113,7 @@ namespace mapnik {
explicit octree(unsigned max_colors=256)
: max_colors_(max_colors),
colors_(0),
offset_(0),
leaf_level_(InsertPolicy::MAX_LEVELS),
has_alfa_(false),
root_(new node())
@ -119,6 +121,21 @@ namespace mapnik {
~octree() { delete root_;}
void setMaxColors(unsigned max_colors)
{
max_colors_ = max_colors;
}
void setOffset(unsigned offset)
{
offset_ = offset;
}
unsigned getOffset()
{
return offset_;
}
void hasAlfa(bool v)
{
has_alfa_=v;
@ -168,7 +185,7 @@ namespace mapnik {
node * cur_node = root_;
while (cur_node)
{
if (cur_node->count != 0) return cur_node->index;
if (cur_node->count != 0) return cur_node->index + offset_;
unsigned idx = InsertPolicy::index_from_level(level,c);
cur_node = cur_node->children_[idx];
++level;
@ -190,22 +207,22 @@ namespace mapnik {
void reduce()
{
reducible_[0].push_back(root_);
// sort reducible
for (unsigned i=0;i<InsertPolicy::MAX_LEVELS;++i)
{
std::sort(reducible_[i].begin(), reducible_[i].end(),node_cmp());
}
while ( colors_ >= max_colors_ - 1)
while ( colors_ > max_colors_ && colors_ > 1)
{
while (leaf_level_ >0 && reducible_[leaf_level_-1].size() == 0)
{
--leaf_level_;
}
if (leaf_level_ < 1) continue;
if ( reducible_[leaf_level_-1].size() == 0) return;
if (leaf_level_ <= 0) return;
// select best of all reducible:
unsigned red_idx = leaf_level_-1;

266
include/mapnik/png_io.hpp
View file

@ -30,6 +30,23 @@ extern "C"
#include <png.h>
}
// TODO - consider exposing this option to user
// static number of alpha ranges in png256 format
// 2 results in smallest image, 3 is minimum for semitransparency, 4 is recommended, anything else is worse
#define TRANSPARENCY_LEVELS 4
#ifdef MAPNIK_BIG_ENDIAN
#define U2RED(x) (((x)>>24)&0xff)
#define U2GREEN(x) (((x)>>16)&0xff)
#define U2BLUE(x) (((x)>>8)&0xff)
#define U2ALPHA(x) ((x)&0xff)
#else
#define U2RED(x) ((x)&0xff)
#define U2GREEN(x) (((x)>>8)&0xff)
#define U2BLUE(x) (((x)>>16)&0xff)
#define U2ALPHA(x) (((x)>>24)&0xff)
#endif
namespace mapnik {
template <typename T>
@ -92,75 +109,109 @@ namespace mapnik {
}
template <typename T>
void reduce_8 (T const& in, image_data_8 & out, octree<rgb> & tree)
void reduce_8 (T const& in, ImageData8 & out, octree<rgb> trees[], unsigned limits[], std::vector<unsigned> &alpha)
{
unsigned width = in.width();
unsigned height = in.height();
unsigned alphaCount[alpha.size()];
for(unsigned i=0; i<alpha.size(); i++)
{
alpha[i] = 0;
alphaCount[i] = 0;
}
for (unsigned y = 0; y < height; ++y)
{
mapnik::image_data_32::pixel_type const * row = in.getRow(y);
mapnik::image_data_8::pixel_type * row_out = out.getRow(y);
mapnik::ImageData32::pixel_type const * row = in.getRow(y);
mapnik::ImageData8::pixel_type * row_out = out.getRow(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
#ifdef MAPNIK_BIG_ENDIAN
mapnik::rgb c((val>>24)&0xff, (val>>16)&0xff, (val>>8) & 0xff);
byte index = tree.quantize(c);
if (!(val&0x80)) index = 0;//alfa
#else
mapnik::rgb c((val)&0xff, (val>>8)&0xff, (val>>16) & 0xff);
byte index = tree.quantize(c);
if (!((val>>24)&0x80)) index = 0;//alfa
#endif
mapnik::rgb c(U2RED(val), U2GREEN(val), U2BLUE(val));
byte index = 0;
int idx = -1;
for(int j=TRANSPARENCY_LEVELS-1; j>0; j--){
if (U2ALPHA(val)>=limits[j]) {
index = idx = trees[j].quantize(c);
break;
}
}
if (idx>=0 && idx<(int)alpha.size())
{
alpha[idx]+=U2ALPHA(val);
alphaCount[idx]++;
}
row_out[x] = index;
}
}
for(unsigned i=0; i<alpha.size(); i++)
{
if (alphaCount[i]!=0)
alpha[i] /= alphaCount[i];
}
}
template <typename T>
void reduce_4 (T const& in, image_data_8 & out, octree<rgb> & tree)
void reduce_4 (T const& in, ImageData8 & out, octree<rgb> trees[], unsigned limits[], std::vector<unsigned> &alpha)
{
unsigned width = in.width();
unsigned height = in.height();
unsigned alphaCount[alpha.size()];
for(unsigned i=0; i<alpha.size(); i++)
{
alpha[i] = 0;
alphaCount[i] = 0;
}
for (unsigned y = 0; y < height; ++y)
{
mapnik::image_data_32::pixel_type const * row = in.getRow(y);
mapnik::image_data_8::pixel_type * row_out = out.getRow(y);
mapnik::ImageData32::pixel_type const * row = in.getRow(y);
mapnik::ImageData8::pixel_type * row_out = out.getRow(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
#ifdef MAPNIK_BIG_ENDIAN
mapnik::rgb c((val>>24)&0xff, (val>>16)&0xff, (val>>8) & 0xff);
byte index = tree.quantize(c);
mapnik::rgb c(U2RED(val), U2GREEN(val), U2BLUE(val));
byte index = 0;
int idx=-1;
for(int j=TRANSPARENCY_LEVELS-1; j>0; j--){
if (U2ALPHA(val)>=limits[j]) {
index = idx = trees[j].quantize(c);
break;
}
}
if (idx>=0 && idx<(int)alpha.size())
{
alpha[idx]+=U2ALPHA(val);
alphaCount[idx]++;
}
if (x%2 == 0) index = index<<4;
if (!(val&0x80)) index = 0;//alfa
#else
mapnik::rgb c((val)&0xff, (val>>8)&0xff, (val>>16) & 0xff);
byte index = tree.quantize(c);
if (x%2 == 0) index = index<<4;
if (!((val>>24)&0x80)) index = 0;//alfa
#endif
row_out[x>>1] |= index;
}
}
for(unsigned i=0; i<alpha.size(); i++)
{
if (alphaCount[i]!=0)
alpha[i] /= alphaCount[i];
}
}
// 1-bit but only one color.
template <typename T>
void reduce_1(T const&, image_data_8 & out, octree<rgb> &)
void reduce_1(T const&, ImageData8 & out, octree<rgb> trees[], unsigned limits[], std::vector<unsigned> &alpha)
{
out.set(0); // only one color!!!
}
template <typename T>
void save_as_png(T & file, std::vector<mapnik::rgb> & palette,
mapnik::image_data_8 const& image,
mapnik::ImageData8 const& image,
unsigned width,
unsigned height,
unsigned color_depth,
bool hasAlfa)
std::vector<unsigned> &alpha)
{
png_voidp error_ptr=0;
png_structp png_ptr=png_create_write_struct(PNG_LIBPNG_VER_STRING,
@ -196,11 +247,17 @@ namespace mapnik {
png_set_PLTE(png_ptr,info_ptr,reinterpret_cast<png_color*>(&palette[0]),palette.size());
// make transparent lowest indexes, so tRNS is small
if (hasAlfa)
if (alpha.size()>0)
{
byte trans[] = {0,0,0,0};
//png_color_16p unused;
png_set_tRNS(png_ptr, info_ptr, (png_bytep)trans, 1, NULL);
png_byte trans[alpha.size()];
unsigned alphaSize=0;//truncate to nonopaque values
for(unsigned i=0; i<alpha.size(); i++){
trans[i]=alpha[i];
if (alpha[i]<255)
alphaSize = i+1;
}
if (alphaSize>0)
png_set_tRNS(png_ptr, info_ptr, (png_bytep)trans, alphaSize, NULL);
}
png_write_info(png_ptr, info_ptr);
@ -216,61 +273,152 @@ namespace mapnik {
template <typename T1,typename T2>
void save_as_png256(T1 & file, T2 const& image)
{
octree<rgb> tree(256);
unsigned width = image.width();
unsigned height = image.height();
unsigned alphaHist[256];//transparency histogram
unsigned semiCount = 0;//sum of semitransparent pixels
unsigned meanAlpha = 0;
for(int i=0; i<256; i++){
alphaHist[i] = 0;
}
for (unsigned y = 0; y < height; ++y){
for (unsigned x = 0; x < width; ++x){
unsigned val = U2ALPHA((unsigned)image.getRow(y)[x]);
alphaHist[val]++;
meanAlpha += val;
if (val>0 && val<255)
semiCount++;
}
}
meanAlpha /= width*height;
// transparency ranges division points
unsigned limits[TRANSPARENCY_LEVELS+1];
limits[0] = 0;
limits[1] = (alphaHist[0]>0)?1:0;
limits[TRANSPARENCY_LEVELS] = 256;
unsigned alphaHistSum = 0;
for(int j=1; j<TRANSPARENCY_LEVELS; j++)
limits[j] = limits[1];
for(int i=1; i<256; i++){
alphaHistSum += alphaHist[i];
for(int j=1; j<TRANSPARENCY_LEVELS; j++){
if (alphaHistSum<semiCount*(j)/4)
limits[j] = i;
}
}
// avoid too wide full transparent range
if (limits[1]>256/(TRANSPARENCY_LEVELS-1))
limits[1]=256/(TRANSPARENCY_LEVELS-1);
// avoid too wide full opaque range
if (limits[TRANSPARENCY_LEVELS-1]<212)
limits[TRANSPARENCY_LEVELS-1]=212;
if (TRANSPARENCY_LEVELS==2) {
limits[1]=127;
}
// estimated number of colors from palette assigned to chosen ranges
unsigned cols[TRANSPARENCY_LEVELS];
// count colors
for(int j=1; j<=TRANSPARENCY_LEVELS; j++) {
cols[j-1] = 0;
for(unsigned i=limits[j-1]; i<limits[j]; i++){
cols[j-1] += alphaHist[i];
}
}
unsigned divCoef = width*height-cols[0];
if (divCoef==0) divCoef = 1;
cols[0] = cols[0]>0?1:0; // fully transparent color (one or not at all)
unsigned usedColors = cols[0];
for(int j=1; j<TRANSPARENCY_LEVELS-1; j++){
unsigned oldCols = cols[j];
cols[j] = cols[j]*(256-cols[0])/divCoef;
if (oldCols>12 && cols[j]<12)
cols[j] = 12; // reserve at least 12 colors to have any effect
usedColors += cols[j];
}
// use rest for most opaque group of pixels
cols[TRANSPARENCY_LEVELS-1] = 256-usedColors;
// octree table for separate alpha range with 1-based index (0 is fully transparent: no color)
octree<rgb> trees[TRANSPARENCY_LEVELS];
for(int j=1; j<TRANSPARENCY_LEVELS; j++)
trees[j].setMaxColors(cols[j]);
for (unsigned y = 0; y < height; ++y)
{
typename T2::pixel_type const * row = image.getRow(y);
for (unsigned x = 0; x < width; ++x)
{
unsigned val = row[x];
#ifdef MAPNIK_BIG_ENDIAN
if (val&0x80)
{
tree.insert(mapnik::rgb((val>>24)&0xff, (val>>16)&0xff, (val>>8) & 0xff));
}
#else
if ((val>>24)&0x80)
{
tree.insert(mapnik::rgb((val)&0xff, (val>>8)&0xff, (val>>16) & 0xff));
}
#endif
else
{
tree.hasAlfa(true);
// insert to proper tree based on alpha range
for(int j=TRANSPARENCY_LEVELS-1; j>0; j--){
if (cols[j]>0 && U2ALPHA(val)>=limits[j]) {
trees[j].insert(mapnik::rgb(U2RED(val), U2GREEN(val), U2BLUE(val)));
break;
}
}
}
}
unsigned leftovers = 0;
std::vector<rgb> palette;
tree.create_palette(palette);
assert(palette.size() <= 256);
palette.reserve(256);
if (cols[0])
palette.push_back(rgb(0,0,0));
for(int j=1; j<TRANSPARENCY_LEVELS; j++) {
if (cols[j]>0) {
if (leftovers>0) {
cols[j] += leftovers;
trees[j].setMaxColors(cols[j]);
leftovers = 0;
}
std::vector<rgb> pal;
trees[j].setOffset(palette.size());
trees[j].create_palette(pal);
assert(pal.size() <= 256);
leftovers = cols[j]-pal.size();
cols[j] = pal.size();
for(unsigned i=0; i<pal.size(); i++){
palette.push_back(pal[i]);
}
assert(palette.size() <= 256);
}
}
//transparency values per palette index
std::vector<unsigned> alphaTable;
//alphaTable.resize(palette.size());//allow semitransparency also in almost opaque range
alphaTable.resize(palette.size()-cols[TRANSPARENCY_LEVELS-1]);
if (palette.size() > 16 )
{
// >16 && <=256 colors -> write 8-bit color depth
image_data_8 reduced_image(width,height);
reduce_8(image,reduced_image,tree);
save_as_png(file,palette,reduced_image,width,height,8,tree.hasAlfa());
ImageData8 reduced_image(width,height);
reduce_8(image,reduced_image,trees, limits, alphaTable);
save_as_png(file,palette,reduced_image,width,height,8,alphaTable);
}
else if (palette.size() == 1)
{
// 1 color image -> write 1-bit color depth PNG
unsigned image_width = (int(0.125*width) + 7)&~7;
unsigned image_height = height;
image_data_8 reduced_image(image_width,image_height);
reduce_1(image,reduced_image,tree);
save_as_png(file,palette,reduced_image,width,height,1,tree.hasAlfa());
ImageData8 reduced_image(image_width,image_height);
reduce_1(image,reduced_image,trees, limits, alphaTable);
if (meanAlpha<255 && cols[0]==0) {
alphaTable.resize(1);
alphaTable[0] = meanAlpha;
}
save_as_png(file,palette,reduced_image,width,height,1,alphaTable);
}
else
{
// <=16 colors -> write 4-bit color depth PNG
unsigned image_width = (int(0.5*width) + 3)&~3;
unsigned image_height = height;
image_data_8 reduced_image(image_width,image_height);
reduce_4(image,reduced_image,tree);
save_as_png(file,palette,reduced_image,width,height,4,tree.hasAlfa());
ImageData8 reduced_image(image_width,image_height);
reduce_4(image,reduced_image,trees, limits, alphaTable);
save_as_png(file,palette,reduced_image,width,height,4,alphaTable);
}
}
}