From: Matthias Kramm <kramm@quiss.org>
Date: Wed, 31 Mar 2010 00:00:05 +0000 (-0700)
Subject: improved png compression
X-Git-Tag: version-0-9-1~63
X-Git-Url: http://git.asbjorn.biz/?a=commitdiff_plain;h=27fe979dab6d4d058d5e608b8057f698804c93bf;p=swftools.git
improved png compression
---
diff --git a/lib/png.c b/lib/png.c
index 1738151..7190553 100644
--- a/lib/png.c
+++ b/lib/png.c
@@ -23,6 +23,7 @@
#include <math.h>
#include <fcntl.h>
#include <zlib.h>
+#include <limits.h>
#ifdef EXPORT
#undef EXPORT
@@ -830,11 +831,10 @@ static colornum_t* getColors(COL*image, int size, int*num)
return colors;
}
-static COL* getOptimalPalette(COL*image, int size, int palettesize)
+static void getOptimalPalette(COL*image, int size, int palettesize, COL*palette)
{
int num;
- COL* ret = malloc(sizeof(COL)*palettesize);
- memset(ret, 0, sizeof(COL)*palettesize);
+ memset(palette, 0, sizeof(COL)*256);
colornum_t*colors = getColors(image, size, &num);
assert(palettesize<=256);
@@ -846,12 +846,12 @@ static COL* getOptimalPalette(COL*image, int size, int palettesize)
the image anyway, we are done */
int t;
for(t=0;t<num;t++) {
- ret[t].r = colors[t].color;
- ret[t].g = colors[t].color>>8;
- ret[t].b = colors[t].color>>16;
- ret[t].a = 255;
+ palette[t].r = colors[t].color;
+ palette[t].g = colors[t].color>>8;
+ palette[t].b = colors[t].color>>16;
+ palette[t].a = 255;
}
- return ret;
+ return;
}
if(num>2048) {
@@ -928,22 +928,20 @@ static COL* getOptimalPalette(COL*image, int size, int palettesize)
free(belongsto);
free(colors);
for(t=0;t<palettesize;t++) {
- ret[t].r = centers[t].color;
- ret[t].g = centers[t].color>>8;
- ret[t].b = centers[t].color>>16;
- ret[t].a = 255;
+ palette[t].r = centers[t].color;
+ palette[t].g = centers[t].color>>8;
+ palette[t].b = centers[t].color>>16;
+ palette[t].a = 255;
}
free(centers);
- return ret;
}
static int sqr(const int x) {return x*x;}
-static void quantizeImage(unsigned char*_image, int size, int numcolors, unsigned char**newimage, COL**palette)
+static void png_quantize_image(unsigned char*_image, int size, int numcolors, unsigned char**newimage, COL*palette)
{
COL*image = (COL*)_image;
- COL*pal= getOptimalPalette(image, size, numcolors);
- *palette = pal;
+ getOptimalPalette(image, size, numcolors, palette);
*newimage = (unsigned char*)malloc(size);
int t;
for(t=0;t<size;t++) {
@@ -952,15 +950,14 @@ static void quantizeImage(unsigned char*_image, int size, int numcolors, unsigne
int s;
for(s=0;s<numcolors;s++) {
int distance = 0;
- distance += sqr((pal[s].r) - (image[t].r))*5;
- distance += sqr((pal[s].g) - (image[t].g))*6;
- distance += sqr((pal[s].b) - (image[t].b))*4;
+ distance += sqr((palette[s].r) - (image[t].r))*5;
+ distance += sqr((palette[s].g) - (image[t].g))*6;
+ distance += sqr((palette[s].b) - (image[t].b))*4;
if(distance<best) {
best = distance;
bestcol = s;
}
}
- //image[t] = pal[bestcol];
(*newimage)[t] = bestcol;
}
}
@@ -1146,7 +1143,130 @@ static int finishzlib(z_stream*zs, FILE*fi)
return size;
}
-static void filter_line8(int filtermode, unsigned char*dest, unsigned char*src, int width)
+static inline u32 color_hash(COL*col)
+{
+ u32 col32 = *(u32*)col;
+ u32 hash = (col32 >> 17) ^ col32;
+ hash ^= ((hash>>8) + 1) ^ hash;
+ return hash;
+}
+
+static int png_get_number_of_palette_entries(COL*img, int width, int height, COL*palette, char*has_alpha)
+{
+ int len = width*height;
+ int t;
+ int palsize = 0;
+ int size[256];
+ int palette_overflow = 0;
+ u32 lastcol32 = 0;
+
+ memset(size, 0, sizeof(size));
+
+ u32*pal = (u32*)malloc(65536*sizeof(u32));
+ int*count = (int*)malloc(65536*sizeof(int));
+
+ assert(sizeof(COL)==sizeof(u32));
+ assert(width && height);
+
+ lastcol32 = (*(u32*)&img[0])^0xffffffff; // don't match
+
+ for(t=0;t<len;t++) {
+ u32 col32 = *(u32*)&img[t];
+ if(col32 == lastcol32)
+ continue;
+
+ if(img[t].a!=255)
+ *has_alpha=1;
+ int i;
+
+ u32 hash = color_hash(&img[t])&255;
+
+ int csize = size[hash];
+ u32*cpal = &pal[hash*256];
+ int*ccount = &count[hash*256];
+ for(i=0;i<csize;i++) {
+ if(col32 == cpal[i]) {
+ ccount[i]++;
+ break;
+ }
+ }
+ if(i==csize) {
+ if(palsize==256) {
+ palette_overflow = 1;
+ break;
+ }
+ count[size[hash]] = 1;
+ cpal[size[hash]++] = col32;
+ palsize++;
+ }
+ lastcol32 = col32;
+ }
+ if(palette_overflow) {
+ free(pal);
+ *has_alpha=1;
+ return width*height;
+ }
+ if(palette) {
+ int i = 0;
+ int occurences[256];
+ for(t=0;t<256;t++) {
+ int s;
+ int csize = size[t];
+ u32* cpal = &pal[t*256];
+ int* ccount = &count[t*256];
+ for(s=0;s<csize;s++) {
+ occurences[i] = ccount[s];
+ palette[i++] = *(COL*)(&cpal[s]);
+ }
+ }
+ assert(i==palsize);
+ int j;
+ for(i=0;i<palsize-1;i++) {
+ for(j=i+1;j<palsize;j++) {
+ if(occurences[j] < occurences[i]) {
+ int o = occurences[i];
+ COL c = palette[i];
+ occurences[i] = occurences[j];
+ palette[i] = palette[j];
+ occurences[j] = o;
+ palette[j] = c;
+ }
+ }
+ }
+ }
+ free(pal);
+ free(count);
+ return palsize;
+}
+
+static void png_map_to_palette(COL*src, unsigned char*dest, int size, COL*palette, int palette_size)
+{
+ int t;
+ int palette_hash[1024];
+ memset(palette_hash, 0, sizeof(int)*1024);
+
+ for(t=0;t<palette_size;t++) {
+ u32 hash = color_hash(&palette[t])&1023;
+ while(palette_hash[hash])
+ hash = (hash+1)&1023;
+ palette_hash[hash] = t;
+ }
+
+ for(t=0;t<size;t++) {
+ u32 hash = color_hash(&src[t]);
+ int index = 0;
+ while(1) {
+ hash&=1023;
+ index = palette_hash[hash];
+ if(!memcmp(&palette[index], &src[t], sizeof(COL)))
+ break;
+ hash++;
+ }
+ dest[t] = palette_hash[hash];
+ }
+}
+
+static int png_apply_specific_filter_8(int filtermode, unsigned char*dest, unsigned char*src, int width)
{
int pos2 = 0;
int pos = 0;
@@ -1186,9 +1306,10 @@ static void filter_line8(int filtermode, unsigned char*dest, unsigned char*src,
pos++;
}
}
+ return filtermode;
}
-static void filter_line32(int filtermode, unsigned char*dest, unsigned char*src, int width)
+static int png_apply_specific_filter_32(int filtermode, unsigned char*dest, unsigned char*src, int width)
{
int pos2 = 0;
int pos = 0;
@@ -1254,6 +1375,79 @@ static void filter_line32(int filtermode, unsigned char*dest, unsigned char*src,
pos+=4;
}
}
+ return filtermode;
+}
+
+static int*num_bits_table = 0;
+
+static void make_num_bits_table()
+{
+ if(num_bits_table) return;
+ num_bits_table = malloc(sizeof(num_bits_table[0])*256);
+ int t;
+ for(t=0;t<256;t++) {
+ int bits=0;
+ int v = t;
+ while(v) {
+ bits++;
+ v&=v-1;
+ }
+ num_bits_table[t]=bits;
+ }
+}
+
+static int png_apply_filter(unsigned char*dest, unsigned char*src, int width, int y, int bpp)
+{
+ make_num_bits_table();
+
+ int num_filters = y>0?5:2; //don't apply y-direction filter in first line
+ int f;
+ int best_nr = 0;
+ int best_energy = INT_MAX;
+ int w = width*(bpp/8);
+ unsigned char* pairs = malloc(8192);
+ assert(bpp==8 || bpp==32);
+ for(f=0;f<num_filters;f++) {
+ if(bpp==8)
+ png_apply_specific_filter_8(f, dest, src, width);
+ else
+ png_apply_specific_filter_32(f, dest, src, width);
+ int x;
+
+ /* approximation for zlib compressability: test how many different
+ (byte1,byte2) occur */
+ memset(pairs, 0, 8192);
+ int different_pairs = 0;
+ for(x=0;x<w-1;x++) {
+ int v = dest[x+1]<<8|dest[x];
+ int p = v>>3;
+ int b = 1<<(v&7);
+ if(!pairs[p]&b) {
+ pairs[p]|=b;
+ different_pairs ++;
+ }
+ }
+ int energy = different_pairs;
+ if(energy<best_energy) {
+ best_nr = f;
+ best_energy = energy;
+ }
+ }
+ if(bpp==8)
+ png_apply_specific_filter_8(best_nr, dest, src, width);
+ else
+ png_apply_specific_filter_32(best_nr, dest, src, width);
+ free(pairs);
+ return best_nr;
+}
+
+int png_apply_filter_8(unsigned char*dest, unsigned char*src, int width, int y)
+{
+ png_apply_filter(dest, src, width, y, 8);
+}
+int png_apply_filter_32(unsigned char*dest, unsigned char*src, int width, int y)
+{
+ png_apply_filter(dest, src, width, y, 32);
}
EXPORT void savePNG(const char*filename, unsigned char*data, int width, int height, int numcolors)
@@ -1274,20 +1468,32 @@ EXPORT void savePNG(const char*filename, unsigned char*data, int width, int heig
u32 tmp32;
int bpp;
int ret;
+ char has_alpha=0;
z_stream zs;
- COL*palette=0;
+ COL palette[256];
make_crc32_table();
if(!numcolors) {
- bpp = 32;
- cols = 0;
- format = 5;
+ int num = png_get_number_of_palette_entries((COL*)data, width, height, palette, &has_alpha);
+ if(num<=255) {
+ //printf("image has %d different colors (alpha=%d)\n", num, has_alpha);
+ data2 = malloc(width*height);
+ png_map_to_palette((COL*)data, data2, width*height, palette, num);
+ data = data2;
+ bpp = 8;
+ cols = num;
+ format = 3;
+ } else {
+ bpp = 32;
+ cols = 0;
+ format = 5;
+ }
} else {
bpp = 8;
cols = numcolors;
format = 3;
- quantizeImage(data, width*height, numcolors, &data, &palette);
+ png_quantize_image(data, width*height, numcolors, &data, palette);
}
datalen = (width*height*bpp/8+cols*8);
@@ -1317,14 +1523,23 @@ EXPORT void savePNG(const char*filename, unsigned char*data, int width, int heig
png_end_chunk(fi);
if(format == 3) {
- png_start_chunk(fi, "PLTE", 768);
- for(t=0;t<cols;t++) {
- png_write_byte(fi,palette[t].r);
- png_write_byte(fi,palette[t].g);
- png_write_byte(fi,palette[t].b);
- }
+ png_start_chunk(fi, "PLTE", cols*3);
+ for(t=0;t<cols;t++) {
+ png_write_byte(fi,palette[t].r);
+ png_write_byte(fi,palette[t].g);
+ png_write_byte(fi,palette[t].b);
+ }
png_end_chunk(fi);
+
+ if(has_alpha) {
+ png_start_chunk(fi, "tRNS", cols);
+ for(t=0;t<cols;t++) {
+ png_write_byte(fi,palette[t].a);
+ }
+ png_end_chunk(fi);
+ }
}
+
long idatpos = png_start_chunk(fi, "IDAT", 0);
memset(&zs,0,sizeof(z_stream));
@@ -1334,7 +1549,7 @@ EXPORT void savePNG(const char*filename, unsigned char*data, int width, int heig
zs.opaque = Z_NULL;
zs.next_out = writebuf;
zs.avail_out = ZLIB_BUFFER_SIZE;
- ret = deflateInit(&zs, 9);
+ ret = deflateInit(&zs, Z_BEST_COMPRESSION);
if (ret != Z_OK) {
fprintf(stderr, "error in deflateInit(): %s", zs.msg?zs.msg:"unknown");
return;
@@ -1353,21 +1568,23 @@ EXPORT void savePNG(const char*filename, unsigned char*data, int width, int heig
else if(bypp==4)
linelen = 1 + ((srcwidth+3)&~3);
unsigned char* line = (unsigned char*)malloc(linelen);
- unsigned char* bestline = (unsigned char*)malloc(linelen);
memset(line, 0, linelen);
+#if 0
+ unsigned char* bestline = (unsigned char*)malloc(linelen);
+ memset(bestline, 0, linelen);
for(y=0;y<height;y++)
{
int filtermode;
int bestsize = 0x7fffffff;
- for(filtermode=0;filtermode<=0;filtermode++) {
+ for(filtermode=0;filtermode<=4;filtermode++) {
if(!y && filtermode>=2)
continue; // don't do y direction filters in the first row
line[0]=filtermode; //filter type
if(bpp==8)
- filter_line8(filtermode, line+1, &data[y*srcwidth], width);
+ png_apply_specific_filter_8(filtermode, line+1, &data[y*srcwidth], width);
else
- filter_line32(filtermode, line+1, &data[y*srcwidth], width);
+ png_apply_specific_filter_32(filtermode, line+1, &data[y*srcwidth], width);
int size = test_line(&zs, line, linelen);
if(size < bestsize) {
@@ -1377,7 +1594,18 @@ EXPORT void savePNG(const char*filename, unsigned char*data, int width, int heig
}
idatsize += compress_line(&zs, bestline, linelen, fi);
}
- free(line);free(bestline);
+ free(bestline);
+#else
+ for(y=0;y<height;y++) {
+ if(bpp==8)
+ line[0] = png_apply_filter_8(line+1, &data[y*srcwidth], width, y);
+ else
+ line[0] = png_apply_filter_32(line+1, &data[y*srcwidth], width, y);
+
+ idatsize += compress_line(&zs, line, linelen, fi);
+ }
+#endif
+ free(line);
}
idatsize += finishzlib(&zs, fi);
png_patch_len(fi, idatpos, idatsize);
@@ -1387,7 +1615,8 @@ EXPORT void savePNG(const char*filename, unsigned char*data, int width, int heig
png_end_chunk(fi);
free(writebuf);
- free(data2);
+ if(data2)
+ free(data2);
fclose(fi);
}