试试这个Effective gif/image color quantization? 它也是基于直方图颜色量化的，与您的方法非常相似，但它直接从 15 位颜色创建直方图以节省空间，并且不使用 bin，而是按出现次数对颜色进行排序，并使用最小距离在调色板阈值中使用颜色以避免几乎重复的颜色...几年前我为我的 GIF 编码器库开发了它...
如果我将此作为输入（转换为 jpg）：
并在没有抖动的情况下使用我的算法我得到了这个结果：
启用抖动后，我得到了这个结果：
正如您在猫耳上看到的，抖动效果要好得多，但即使没有抖动，结果也比您的要好。
然而，多年来，调色板计算代码（从链接答案中发布的那个）演变为这个（C++）：
void gif::compute_palette0()
{
int x,y,r0,g0,b0,r,g,b,a,aa,c,e,hists;
DWORD i,i0,cc;
union { DWORD dd; BYTE db[4]; } c0,c1;
DWORD his[32768];
DWORD idx[32768];
// 15bit histogram
for (x=0;x<32768;x++) { his[x]=0; idx[x]=x; }
for (y=0;y<ys;y++)
for (x=0;x<xs;x++)
{
cc=pic.pyx[y][x];
cc=((cc>>3)&0x1F)|((cc>>6)&0x3E0)|((cc>>9)&0x7C00);
if (his[cc]<0xFFFFFFFF) his[cc]++;
}
// add RGB shades combinations for dithering
if (_dither)
{
x=xs*ys; // max possible count to make as start colors in palette
for (r=0;r<32;r+=10)
for (g=0;g<32;g+=10)
for (b=0;b<32;b+=10,x++)
his[(r<<10)|(g<<5)|( b)]=x;
}
// set recolor as unused
for (r0=0;r0<32;r0++)
for (g0=0;g0<32;g0++)
for (b0=0;b0<32;b0++)
recolor[r0][g0][b0]=255;
// remove zeroes
for (x=0,y=0;y<32768;y++)
{
his[x]=his[y];
idx[x]=idx[y];
if (his[x]) x++;
} hists=x;
// sort by hist
for (i=1,e=hists;i;e--)
for (i=0,x=0,y=1;y<e;x++,y++)
if (his[x]<his[y])
{
i=his[x]; his[x]=his[y]; his[y]=i;
i=idx[x]; idx[x]=idx[y]; idx[y]=i; i=1;
}
// set lcolor color palete
for (i0=0,x=0;x<hists;x++) // main colors
{
cc=idx[x];
b= cc &31;
g=(cc>> 5)&31;
r=(cc>>10)&31;
c0.db[0]=b;
c0.db[1]=g;
c0.db[2]=r;
c0.dd=(c0.dd<<3)&0x00F8F8F8;
// skip if similar color already in lcolor[]
for (a=0,i=0;i<i0;i++)
{
c1.dd=lcolor[i];
aa=int(BYTE(c1.db[0]))-int(BYTE(c0.db[0])); if (aa<=0) aa=-aa; a =aa;
aa=int(BYTE(c1.db[1]))-int(BYTE(c0.db[1])); if (aa<=0) aa=-aa; a+=aa;
aa=int(BYTE(c1.db[2]))-int(BYTE(c0.db[2])); if (aa<=0) aa=-aa; a+=aa;
if (a<=16) { a=1; break; } a=0; // *** treshold ***
}
if (a) recolor[r][g][b]=i;
else{
recolor[r][g][b]=i0;
lcolor[i0]=c0.dd; i0++;
if (i0>=DWORD(lcolors)) { x++; break; }
}
} // i0 = new color table size
for (;x<hists;x++) // minor colors
{
cc=idx[x];
b= cc &31;
g=(cc>> 5)&31;
r=(cc>>10)&31;
c0.db[0]=b;
c0.db[1]=g;
c0.db[2]=r;
c0.dd=(c0.dd<<3)&0x00F8F8F8;
// find closest color
int dc=-1; DWORD ii=0;
for (a=0,i=0;i<i0;i++)
{
c1.dd=lcolor[i];
aa=int(BYTE(c1.db[0]))-int(BYTE(c0.db[0])); if (aa<=0) aa=-aa; a =aa;
aa=int(BYTE(c1.db[1]))-int(BYTE(c0.db[1])); if (aa<=0) aa=-aa; a+=aa;
aa=int(BYTE(c1.db[2]))-int(BYTE(c0.db[2])); if (aa<=0) aa=-aa; a+=aa;
if ((dc<0)||(dc>a)) { dc=a; ii=i; }
}
recolor[r][g][b]=ii;
}
encode_palette_compute(true);
if ((frame)&&(hists<lcolors))
for (lcolor_bits=1,lcolors=1<<lcolor_bits;lcolors<hists;lcolors<<=1,lcolor_bits++);
// compute recolor for 16 base colors for all yet unused colors
for (r0=0;r0<32;r0++)
for (g0=0;g0<32;g0++)
for (b0=0;b0<32;b0++)
if (recolor[r0][g0][b0]==255)
{
// find closest color
for (i=0,c=-1;i<16;i++)
{
c0.dd=lcolor[i];
b=WORD(c0.db[0])>>3;
g=WORD(c0.db[1])>>3;
r=WORD(c0.db[2])>>3;
a=(r-r0); aa =a*a;
a=(g-g0); aa+=a*a;
a=(b-b0); aa+=a*a;
if ((c<0)||(e>aa)) { e=aa; c=i; }
}
recolor[r0][g0][b0]=c;
}
}
我的gif 类看起来像这样（因此您可以提取配置和使用的变量...）：
class gif
{
public:
// IO interface
file_cache<4<<20> fi,fo; // file cache
BYTE dat[256]; // internal buffer 256 Bytes needed
// Performance counter
double Tms,tms,tdec,tenc; // perioda citaca [ms], zmerany cas [ms],cas encodovania [ms]
void tbeg(); // zaciatok merania
void tend(); // koniec merania
// image data
gif_frame32 pic,pic0; // actual and restore to 32bit frames
gif_frame8 pic1; // 8bit input conversion frame
int xs,ys; // resolution
int *py; // interlace table
// colors (colors are computed from color_bits)
DWORD gcolor[256]; //hdr
DWORD lcolor[256]; //img
BYTE recolor[32][32][32]; //encode reduce color table
int scolors,scolor_bits; //hdr screen color depth
int gcolors,gcolor_bits; //hdr global pallete
int lcolors,lcolor_bits; //img/hdr local palette
// info
bool _89a; //hdr extensions present?
bool _interlaced; //img interlaced frame?
bool _gcolor_table; //hdr
bool _gcolor_sorted; //hdr
bool _lcolor_table; //img local palette present?
bool _lcolor_sorted; //img local palette colors sorted?
int cpf,cpf_error; //clears per frame counter,clear_errors total
// debug
bool _draw_palette; //draw pallete?
// animation
int frame,disposal; // frame ix,disposal of frame
double t,tn; // animation time,next frame time
// encode config
int _force_disposal; // -1 or forced disposal
bool _precomputed_palette; // if true recolor and global palete is already set before encoding
bool _dither; // dither colors?
// inter thread comm
volatile bool _image_copied; // flag that source image is not needed anymore while encoding
// temp dictionary for dec/enc
gif_str dict[_gif_maxdecode];
DWORD dicts,code_clr,code_end,code_min;
// temp dictionary speed up tables (encoding)
WORD dtab[256][_gif_maxencode],dnum[256],dmask[256]; // dtab[i][dnum[i]] all dictionary codes (sorted by code) starting with i for encode speed up, 1<<dmask[i]<=dnum[i]
#pragma pack(1)
struct __hdr
{
// Header
BYTE Signature[3]; /* Header Signature (always "GIF") */
BYTE Version[3]; /* GIF format version("87a" or "89a") */
// Logical Screen Descriptor
WORD xs;
WORD ys;
BYTE Packed; /* Screen and Color Map Information */
BYTE BackgroundColor; /* Background Color Index */
BYTE AspectRatio; /* Pixel Aspect Ratio */
__hdr(){}; __hdr(__hdr& a){ *this=a; }; ~__hdr(){}; __hdr* operator = (const __hdr *a) { *this=*a; return this; }; /*__hdr* operator = (const __hdr &a) { ...copy... return this; };*/
};
struct _hdr:__hdr
{
DWORD adr,siz;
_hdr(){}; _hdr(_hdr& a){ *this=a; }; ~_hdr(){}; _hdr* operator = (const _hdr *a) { *this=*a; return this; }; /*_hdr* operator = (const _hdr &a) { ...copy... return this; };*/
} hdr;
struct __img
{
// Logical Image Descriptor
BYTE Separator; /* Image Descriptor identifier 0x2C */
WORD x0; /* X position of image on the display */
WORD y0; /* Y position of image on the display */
WORD xs; /* Width of the image in pixels */
WORD ys; /* Height of the image in pixels */
BYTE Packed; /* Image and Color Table Data Information */
__img(){}; __img(__img& a){ *this=a; }; ~__img(){}; __img* operator = (const __img *a) { *this=*a; return this; }; /*__img* operator = (const __img &a) { ...copy... return this; };*/
};
struct _img:__img
{
DWORD adr,siz;
_img(){}; _img(_img& a){ *this=a; }; ~_img(){}; _img* operator = (const _img *a) { *this=*a; return this; }; /*_img* operator = (const _img &a) { ...copy... return this; };*/
} img;
struct __gfxext
{
BYTE Introducer; /* Extension Introducer (always 21h) */
BYTE Label; /* Graphic Control Label (always F9h) */
BYTE BlockSize; /* Size of remaining fields (always 04h) */
BYTE Packed; /* Method of graphics disposal to use */
WORD DelayTime; /* Hundredths of seconds to wait */
BYTE ColorIndex; /* Transparent Color Index */
BYTE Terminator; /* Block Terminator (always 0) */
__gfxext(){}; __gfxext(__gfxext& a){ *this=a; }; ~__gfxext(){}; __gfxext* operator = (const __gfxext *a) { *this=*a; return this; }; /*__gfxext* operator = (const __gfxext &a) { ...copy... return this; };*/
};
struct _gfxext:__gfxext
{
DWORD adr,siz;
_gfxext(){}; _gfxext(_gfxext& a){ *this=a; }; ~_gfxext(){}; _gfxext* operator = (const _gfxext *a) { *this=*a; return this; }; /*_gfxext* operator = (const _gfxext &a) { ...copy... return this; };*/
} gfxext;
struct __txtext
{
BYTE Introducer; /* Extension Introducer (always 21h) */
BYTE Label; /* Extension Label (always 01h) */
BYTE BlockSize; /* Size of Extension Block (always 0Ch) */
WORD TextGridLeft; /* X position of text grid in pixels */
WORD TextGridTop; /* Y position of text grid in pixels */
WORD TextGridWidth; /* Width of the text grid in pixels */
WORD TextGridHeight; /* Height of the text grid in pixels */
BYTE CellWidth; /* Width of a grid cell in pixels */
BYTE CellHeight; /* Height of a grid cell in pixels */
BYTE TextFgColorIndex; /* Text foreground color index value */
BYTE TextBgColorIndex; /* Text background color index value */
// BYTE *PlainTextData; /* The Plain Text data */
// BYTE Terminator; /* Block Terminator (always 0) */
__txtext(){}; __txtext(__txtext& a){ *this=a; }; ~__txtext(){}; __txtext* operator = (const __txtext *a) { *this=*a; return this; }; /*__txtext* operator = (const __txtext &a) { ...copy... return this; };*/
};
struct _txtext:__txtext
{
DWORD adr,siz;
AnsiString dat;
_txtext(){}; _txtext(_txtext& a){ *this=a; }; ~_txtext(){}; _txtext* operator = (const _txtext *a) { *this=*a; return this; }; /*_txtext* operator = (const _txtext &a) { ...copy... return this; };*/
};
List<_txtext> txtext;
struct __remext
{
BYTE Introducer; /* Extension Introducer (always 21h) */
BYTE Label; /* Comment Label (always FEh) */
// BYTE *CommentData; /* Pointer to Comment Data sub-blocks */
// BYTE Terminator; /* Block Terminator (always 0) */
__remext(){}; __remext(__remext& a){ *this=a; }; ~__remext(){}; __remext* operator = (const __remext *a) { *this=*a; return this; }; /*__remext* operator = (const __remext &a) { ...copy... return this; };*/
};
struct _remext:__remext
{
DWORD adr,siz;
AnsiString dat;
_remext(){}; _remext(_remext& a){ *this=a; }; ~_remext(){}; _remext* operator = (const _remext *a) { *this=*a; return this; }; /*_remext* operator = (const _remext &a) { ...copy... return this; };*/
};
List<_remext> remext;
struct __appext
{
BYTE Introducer; /* Extension Introducer (always 21h) */
BYTE Label; /* Extension Label (always FFh) */
BYTE BlockSize; /* Size of Extension Block (always 0Bh) */
CHAR Identifier[8]; /* Application Identifier */
BYTE AuthentCode[3]; /* Application Authentication Code */
// BYTE *ApplicationData; /* Point to Application Data sub-blocks */
// BYTE Terminator; /* Block Terminator (always 0) */
__appext(){}; __appext(__appext& a){ *this=a; }; ~__appext(){}; __appext* operator = (const __appext *a) { *this=*a; return this; }; /*__appext* operator = (const __appext &a) { ...copy... return this; };*/
};
struct _appext:__appext
{
DWORD adr,siz;
AnsiString dat;
_appext(){}; _appext(_appext& a){ *this=a; }; ~_appext(){}; _appext* operator = (const _appext *a) { *this=*a; return this; }; /*_appext* operator = (const _appext &a) { ...copy... return this; };*/
};
List<_appext> appext;
#pragma pack()
gif();
gif(gif& a);
~gif();
gif* operator = (const gif *a);
//gif* operator = (const gif &a);
void _resize(int _xs,int _ys); // resize buffers
void load_beg(AnsiString filename); // open GIF file for decoding
void decode(int _ignore_delay=0); // decode frame from GIF, if _ignore_delay then ignore realtime
void load_end(); // close GIF file
void save_beg(AnsiString filename); // create new GIF file for encoding
void compute_palette0(); // compute palette from frame method 0
void compute_palette1(); // compute palette from frame method 1
void encode_palette_RGB256(); // set RGB combinations as 256 color palette as predefined global only palette
void encode_palette_VGA256(); // set default 256 color VGA palette as predefined global only palette
void encode_palette_compute(bool _local); // compute recolor[][][] from palette
void encode(const gif_frame32 &src,int dt=0); // encode frame to GIF , dt is delay in [ms] instead of realtime in range <10 .. 655350> [ms]
// void encode(int dst_xs,int dst_ys,TCanvas *src,int src_x0,int src_y0,int src_x1,int src_y1,int dt=0); // encode frame to GIF , dt is delay in [ms] instead of realtime in range <10 .. 655350> [ms]
void save_end(); // finalize and close GIF file
void draw_info(int x,int y,TCanvas *can);
void draw_info(int x,int y,Graphics::TBitmap *bmp);
void configure(gif &src); // set all encoding variables from src (for multithreaded encoding)
};