肝了一天半，终于做好了，蓝线是三角形，黄线就是voronoi图
然后是处理翻转边的情况的时候，记得递归，把所有影响的边都检查一遍。
然后是判断边是否需要翻转的时候，我尝试用外接圆判断第四个是否在内，但太复杂了，于是就改为判断公共边的对角相加是否大于180度。数据结构很有意思，我做的是第一个点的对边就是第一条边，第一条边的对角就是第一个角，对应着第一个点。
struct Point
{
int x,y;//点的坐标
} p[maxn];
struct Edge
{
int a,b;//连接的两个点的索引
int ta,tb;//连接的两个三角形的索引
} edge[maxn];
struct Triangle
{
int e[3],p[3],use,near[3];//边的索引，点的索引，是否激活，相邻的三角形的索引
double a[3];//三个角的度数，acos计算，值在0到pi之间
} tri[maxn];判断点在哪个三角形里面，如果在边上的话直接丢弃这个点，cal就是计算的叉积，反正只需计算正负，就把叉积归结成1或-1了，如果不这样有可能相乘的两个数字太大。我一开始还计算点积去了2333
for(int k=0; k<=2; k++)
{
if(abs(cal[k])<eps)
{
border=1;
break;
}
else if(cal[k]>0)
cal[k]=1;
else
cal[k] = -1;
}写几个注意点吧。首先是利用三个点算出圆心的时，要注意斜率不存在的情况，这时候圆心的x坐标就是垂直平分线斜率不存在的两个点的中点的x坐标，而不是0。以及浮点到整型需要小心。
if(abs(p1y - p0y) < 1e-5)//斜率k0不存在
{
double k1 = -(p2x-p0x)/(p2y - p0y);
double d1 = m1y - k1*m1x;
double cx = m0x;
double cy = cx*k1 + d1;
printf("m1x = %lf,m1y = %lf,k1 = %lf,d1 = %lf\n",m1x,m1y,k1,d1);
printf("cx = %lf,cy = %lf k0 not exist\n",cx,cy);
cirx[idx] = cx;
ciry[idx] = cy;
printf("cirx = %d,ciry = %d\n",cirx[idx],ciry[idx]);
}然后是圆心如果差的太远，也就是离图片太远了，可能造成拉扯，于是我强行把它们拉回来
if(cirx[i] > width)
cirx[i] = width*1.1;
if(cirx[i] < 0 )
cirx[i] = -width*0.1;
if(ciry[i] > height)
ciry[i] = height*1.1;
if(ciry[i] < 0 )
ciry[i] = -height*0.1;然后源码，main.cpp以及用于输出图片的svpng.inc，很多调试信息没去掉哈哈哈，没想到写这个也要500行左右，很适合挑战了。
#include "svpng.inc"
#include <bits/stdc++.h>
using namespace std;
const int width = 1024,height = 512,intensity = 32;
unsigned char rgba[width * height * 4];
int rgbapix[width*height],mm[3000][3000];
const int possionnumber = intensity*intensity/2,maxn = 100000;
int res[possionnumber],realnumber;
double possionr = width/intensity;
void pixel(int posx,int posy,int colr,int colg,int colb)
{
if(posx < 0 || posx > width || posy < 0 || posy > height)
return;
int idx = posx;
posx = posy,posy = idx,
posx = 512 - posx,idx = posx*1024*4+posy*4;
if(colr>255)
colr=255;
if(colg>255)
colg=255;
if(colb>255)
colb=255;
rgba[idx++]=colr;
rgba[idx++]=colg;
rgba[idx++] = colb;
rgba[idx] = 255;
}
void drawbox(int x,int y,int r,int b,int g)
{
for(int i = x - 1; i < x + 1; i++)
for(int j = y - 1; j < y + 1; j++)
pixel(x,y,r,g,b);
}
struct Point
{
int x,y;
} p[maxn];
int pnum = 0;
struct Edge
{
int a,b;
int ta,tb;//连接的两个三角形
int use;
} edge[maxn];
int edgenum = 0;
int addEdge(int a,int b,int ta,int tb)
{
edge[++edgenum].ta = ta;
edge[edgenum].tb = tb;
edge[edgenum].a = a;
edge[edgenum].b = b;
return edgenum;
}
//修改连接的两点
void editEdge1(int e,int a,int b)
{
edge[e].a = a;
edge[e].b = b;
}
void printEdge(int idx)
{
printf("idx = %d,a = %d,b = %d,ta = %d,tb = %d\n",idx,edge[idx].a,edge[idx].b,edge[idx].ta,edge[idx].tb);
}
//修改连接的三角形
void editEdge2(int e,int oldt,int newt)
{
if(edge[e].ta == oldt)
edge[e].ta = newt;
else
edge[e].tb = newt;
}
struct Triangle
{
int e[3],p[3],use,near[3];
double a[3];
} tri[maxn];
int trinum = 0;
void printTri(int idx)
{
printf("--------------------------------------new tir idx = %d\n",idx);
printf("p0 = %d,p1 = %d,p2 = %d\n",tri[idx].p[0],tri[idx].p[1],tri[idx].p[2]);
printf("p0x = %d,p0y = %d,",p[tri[idx].p[0]].x,p[tri[idx].p[0]].y);
printf("p1x = %d,p1y = %d,",p[tri[idx].p[1]].x,p[tri[idx].p[1]].y);
printf("p2x = %d,p2y = %d\n",p[tri[idx].p[2]].x,p[tri[idx].p[2]].y);
printf("e0 = %d,e1 = %d,e2 = %d\n",tri[idx].e[0],tri[idx].e[1],tri[idx].e[2]);
printf("a0 = %lf,a1 = %lf,a2 = %lf\n",tri[idx].a[0],tri[idx].a[1],tri[idx].a[2]);
}
void deleteTriangle(int idx)
{
tri[idx].use = 0;
}
double calangle(int ce,int p1,int p2)
{
// printf("ce = %d,p1 = %d,p2 = %d\n",ce,p1,p2);
double v1x = p[p1].x - p[ce].x,v1y = p[p1].y - p[ce].y;
double v2x = p[p2].x - p[ce].x,v2y = p[p2].y - p[ce].y;
// printf("v1x = %lf,v1y = %lf,v2x = %lf,v2y = %lf\n",v1x,v1y,v2x,v2y);
double res = acos((v1x*v2x + v1y*v2y)/(sqrt(v1x*v1x + v1y*v1y)*sqrt(v2x*v2x + v2y*v2y)));
printf("res = %lf\n",res);
return res;
}
int addTriangle(int p0,int p1,int p2,int e0,int e1,int e2)
{
tri[++trinum].e[0] = e0;
tri[trinum].e[1] = e1;
tri[trinum].e[2] = e2;
tri[trinum].p[0] = p0;
tri[trinum].p[1] = p1;
tri[trinum].p[2] = p2;
tri[trinum].a[0] = calangle(p0,p1,p2);//0到Pi之间的一个数字
tri[trinum].a[1] = calangle(p1,p0,p2);
tri[trinum].a[2] = calangle(p2,p0,p1);
tri[trinum].near[0] = tri[trinum].near[1] = tri[trinum].near[2] = -1;
tri[trinum].use = 1;
return trinum;
}
void editTriangle(int t1,int t2,int p0,int p1,int p2,int p3,int e0,int e1,int e2,int e3,int e4,int e5)
{
tri[t1].p[0] = p0,tri[t1].p[1] = p1,tri[t1].p[2] = p2;
tri[t1].e[0] = e0,tri[t1].e[1] = e1,tri[t1].e[2] = e2;
tri[t1].a[0] = calangle(p0,p1,p2);
tri[t1].a[1] = calangle(p1,p0,p2);
tri[t1].a[2] = calangle(p2,p0,p1);
//e2是公共边
tri[t2].p[0] = p1,tri[t2].p[1] = p2,tri[t2].p[2] = p3;
tri[t2].e[0] = e3,tri[t2].e[1] = e4,tri[t2].e[2] = e5;
tri[t2].a[0] = calangle(p1,p2,p3);
tri[t2].a[1] = calangle(p2,p3,p1);
tri[t2].a[2] = calangle(p3,p1,p2);
}
void possiondisk()
{
int pnx = intensity,pny = intensity/2,he = 0,ta = 0;
int work[possionnumber];
srand( (unsigned)time( NULL ) );
int x = rand()%width,y = rand()%height;
work[ta] = x + y*width;
res[ta] = x + y*width;
int grididx = x/possionr + y/possionr*pnx;
int grid[pnx*pny];
memset(grid,-1,sizeof(grid));
grid[grididx] = ta;
while(he <= ta && ta < possionnumber)
{
int now = work[he++],nowx = now%width,nowy = now/width;
for(int ix = 0; ix < 30; ix++)
{
int flag = 0;
while(1)
{
x = rand()%width;
y = rand()%height;
double len = sqrt((nowx-x)*(nowx-x) + (nowy - y)*(nowy-y));
if(len < possionr*2 && len > possionr && x > 0 && x < width && y > 0 && y < width)
break;
}
int gridx = x/(int)possionr,gridy = y/(int)possionr;
if(grid[gridx + gridy*pnx] != -1)
continue;
for(int i = gridx - 1; i <= gridx + 1; i++)
{
if(i < 0 || i >= pnx)
continue;
for(int j = gridy - 1; j <= gridy + 1; j++)
{
if(j < 0 || j >= pny)
continue;
if(grid[i + j*pnx] == -1)
continue;
int newx = res[grid[i + j*pnx]]%width,newy = res[grid[i + j*pnx]]/width;
if(sqrt((newx-x)*(newx-x)+(newy-y)*(newy-y)) < possionr)
{
flag = 1;
break;
}
}
}
if(flag == 0)
{
work[++ta] = x + y*width,res[ta] = x + y*width;
grid[gridx + gridy*pnx] = ta;
// printf("res[%d] = %d\n",ta,res[ta]);
}
}
}
realnumber = ta;
for(int i = 0; i <= ta; i++)
drawbox(res[i]%width,res[i]/width,255,0,0);
}
void drawaLine(int x0, int y0, int x1, int y1,int r,int g,int b)
{
printf("x0 = %d,y0 = %d,x1 = %d,y1 = %d\n",x0,y0,x1,y1);
bool steep = false;
if (abs(x0-x1)<abs(y0-y1))
{
swap(x0, y0);
swap(x1, y1);
steep = true;
}
if (x0>x1)
{
swap(x0, x1);
swap(y0, y1);
}
int dx = x1-x0;
int dy = y1-y0;
int derror2 = abs(dy)*2;
int error2 = 0;
int y = y0;
for (int x=x0; x<=x1; x++)
{
if (steep)
{
pixel(y, x, r,g,b);
}
else
{
pixel(x,y,r,g,b);
}
error2 += derror2;
if (error2 > dx)
{
y += (y1>y0?1:-1);
error2 -= dx*2;
}
}
}
void handleedge(int nowe)
{
printf("test!\n");
int TriA = edge[nowe].ta;
int TriB = edge[nowe].tb;
if(TriB == -1)
return;
printTri(TriA);
printTri(TriB);
int ea,eb,f1 = -1,f2,s1 = -1,s2,p0,p1;
for(int k = 0; k < 3; k++)
{
printf("A%d = %d,B%d = %d,nowe = %d\n",k,tri[TriA].e[k],k,tri[TriB].e[k],nowe);
if(tri[TriA].e[k] == nowe)
ea = k;
else if(f1 == -1)
f1 = tri[TriA].e[k];
else
f2 = tri[TriA].e[k];
if(tri[TriB].e[k] == nowe)
eb = k;
else if(s1 == -1)
s1 = tri[TriB].e[k];
else
s2 = tri[TriB].e[k];
}
printf("ea = %d,eb = %d,f1 = %d,f2 = %d,s1 = %d,s2 = %d\n",ea,eb,f1,f2,s1,s2);
double pi = 3.14159;
int flag = 0;
//保证f1和s1相连
if(edge[f1].a == edge[s1].a || edge[f1].a == edge[s1].b || edge[f1].b == edge[s1].a || edge[f1].b == edge[s1].b)
flag=1;
else
flag = s2,s2 = s1,s1 = flag;
printf("f1 = %d,s1 = %d,f1a = %d,f1b = %d,s1a = %d,s1b = %d\n",f1,s1,edge[f1].a,edge[f1].b,edge[s1].a,edge[s1].b);
//保证f1和s1的同一点是p0，同理f2和s2的连接点是p1
if(edge[f1].a == edge[s1].a || edge[f1].a == edge[s1].b)
p0 = edge[f1].a;
else if (edge[f1].b == edge[s1].a || edge[f1].b == edge[s1].b)
p0 = edge[f1].b;
if(edge[f2].a == edge[s2].a || edge[f2].a == edge[s2].b)
p1 = edge[f2].a;
else if (edge[f2].b == edge[s2].a || edge[f2].b == edge[s2].b)
p1 = edge[f2].b;
printf("%lf and %lf\n",tri[TriA].a[ea],tri[TriB].a[eb]);
if(tri[TriA].a[ea] + tri[TriB].a[eb] > pi)
{
printf("Flip!\n");
//p0 , p1原来连接的两点
int pa = tri[TriA].p[ea],pb = tri[TriB].p[eb];//现在要连接的两点
editEdge1(nowe,pa,pb);
printEdge(nowe);
editEdge2(s1,TriB,TriA);
editEdge2(f2,TriA,TriB);
printEdge(f1);
printEdge(f2);
printEdge(s1);
printEdge(s2);
if(edge[f1].a == pb || edge[f1].b == pb)
flag = pb,pb = pa,pa = flag;//保证f1连接的是pa
printf("p0 = %d,p1 = %d,pa = %d,pb = %d\n",p0,p1,pa,pb);
printf("nowe = %d,f1 = %d,f2 = %d,s1 = %d,s2 = %d\n",nowe,f1,f2,s1,s2);
editTriangle(TriA,TriB,p0,pa,pb,p1,nowe,s1,f1,s2,f2,nowe);
printf("after----------------\n");
printTri(TriA);
printTri(TriB);
handleedge(f1);
handleedge(f2);
handleedge(s1);
handleedge(s2);
}
}
void delaunay()
{
int tidx;
p[0].x = -512,p[0].y = -512;
p[1].x = 512,p[1].y = 1536;
p[2].x = 1536,p[2].y = -512;
pnum = 2;
int ae = addEdge(0,1,1,-1);
int be = addEdge(1,2,1,-1);
int ce = addEdge(2,0,1,-1);
addTriangle(0,1,2,be,ce,ae);
/*realnumber = 4;
res[1] = 297 + 137*width;
res[2] = 471 + 385*width;
res[3] = 1013 + 194*width;
res[4] = 561 + 67*width;*/
for(int i = 1; i <= realnumber; i++)
{
//先找这个点在哪个三角形里面
int nowx = res[i]%width,nowy = res[i]/width,border = 0;
for(int j = 1; j <= trinum; j++) // edgenum 和 trinum都是从1开始的
{
if(tri[j].use==0)
continue;
int p0x = p[tri[j].p[0]].x,p0y = p[tri[j].p[0]].y;
int p1x = p[tri[j].p[1]].x,p1y = p[tri[j].p[1]].y;
int p2x = p[tri[j].p[2]].x,p2y = p[tri[j].p[2]].y;
int np0x = nowx-p0x,np0y = nowy-p0y,v0x = p1x-p0x,v0y = p1y-p0y;
int np1x = nowx-p1x,np1y = nowy-p1y,v1x = p2x-p1x,v1y = p2y-p1y;
int np2x = nowx-p2x,np2y = nowy-p2y,v2x = p0x-p2x,v2y = p0y-p2y;
int cal[3];
cal[0] = np0x * v0y - np0y * v0x;
cal[1] = np1x * v1y - np1y * v1x;
cal[2] = np2x * v2y - np2y * v2x;
double eps = 0.1;
for(int k=0; k<=2; k++)
{
if(abs(cal[k])<eps)
{
border=1;
break;
}
else if(cal[k]>0)
cal[k]=1;
else
cal[k] = -1;
}
if(border)
break;
// printf("%d %d %d\n",cal[0],cal[1],cal[2]);
if((cal[0]*cal[1] > 0) && (cal[1]*cal[2]>0))
{
tidx = j;//在这个三角形里面
break;
}
}
if(border)
continue;//不要在边界上的点
printf("---\n%d,%dat %d\n---\n",nowx,nowy,tidx);
deleteTriangle(tidx);
p[++pnum].x = nowx,p[pnum].y = nowy;
int p0 = tri[tidx].p[0],p1 = tri[tidx].p[1],p2 = tri[tidx].p[2];
printf("new Point %d nad %d delete Tri %d\n", nowx,nowy,tidx);
printTri(tidx);
ae = addEdge(pnum,p0,trinum+1,trinum+3);
be = addEdge(pnum,p1,trinum+2,trinum+1);
ce = addEdge(pnum,p2,trinum+3,trinum+2);
int tempe = tri[tidx].e[2],tempt;
tempt = addTriangle(p0,pnum,p1,be,tempe,ae);
if(edge[tempe].ta == tidx)
edge[tempe].ta = tempt;
else
edge[tempe].tb = tempt;
tempe = tri[tidx].e[0];
tempt = addTriangle(p1,pnum,p2,ce,tempe,be);
if(edge[tempe].ta == tidx)
edge[tempe].ta = tempt;
else
edge[tempe].tb = tempt;
tempe = tri[tidx].e[1];
tempt = addTriangle(p2,pnum,p0,ae,tempe,ce);
if(edge[tempe].ta == tidx)
edge[tempe].ta = tempt;
else
edge[tempe].tb = tempt;
for(int j = 0; j < 3; j++)
{
handleedge(tri[tidx].e[j]);
}
}
for(int i = 1; i <= trinum; i++)
{
if(tri[i].use)
{
printTri(i);
drawaLine(p[tri[i].p[0]].x,p[tri[i].p[0]].y,p[tri[i].p[1]].x,p[tri[i].p[1]].y,0,0,255);
drawaLine(p[tri[i].p[1]].x,p[tri[i].p[1]].y,p[tri[i].p[2]].x,p[tri[i].p[2]].y,0,0,255);
drawaLine(p[tri[i].p[2]].x,p[tri[i].p[2]].y,p[tri[i].p[0]].x,p[tri[i].p[0]].y,0,0,255);
for(int j = 0; j < 3; j++)
{
if(edge[tri[i].e[j]].ta == i)
tri[i].near[j]=edge[tri[i].e[j]].tb;
else
tri[i].near[j]=edge[tri[i].e[j]].ta;
}
}
}
}
int cirx[maxn],ciry[maxn];
void calcir(int p0,int p1,int p2,int idx)
{
printf("calcir-----------------\n");
double p0x = p[p0].x,p0y = p[p0].y;
double p1x = p[p1].x,p1y = p[p1].y;
double p2x = p[p2].x,p2y = p[p2].y;
printf("p0x = %lf,p0y = %lf\n",p0x,p0y);
printf("p1x = %lf,p1y = %lf\n",p1x,p1y);
printf("p2x = %lf,p2y = %lf\n",p2x,p2y);
double m0x = (p0x + p1x)/2,m0y = (p0y + p1y)/2;
double m1x = (p0x + p2x)/2,m1y = (p0y + p2y)/2;
if(abs(p1y - p0y) < 1e-5)//斜率k0不存在
{
double k1 = -(p2x-p0x)/(p2y - p0y);
double d1 = m1y - k1*m1x;
double cx = m0x;
double cy = cx*k1 + d1;
printf("m1x = %lf,m1y = %lf,k1 = %lf,d1 = %lf\n",m1x,m1y,k1,d1);
printf("cx = %lf,cy = %lf k0 not exist\n",cx,cy);
cirx[idx] = cx;
ciry[idx] = cy;
printf("cirx = %d,ciry = %d\n",cirx[idx],ciry[idx]);
}
else if(abs(p2y - p0y) < 1e-5)
{
double k0 = -(p1x-p0x)/(p1y - p0y);
double d0 = m0y - k0*m0x;
printf("m0x = %lf,m0y = %lf,k0 = %lf,d0 = %lf\n",m0x,m0y,k0,d0);
double cx = m0x;
double cy = cx*k0 + d0;
printf("cx = %lf,cy = %lf,k1 not exist\n",cx,cy);
cirx[idx] = cx;
ciry[idx] = cy;
printf("cirx = %d,ciry = %d\n",cirx[idx],ciry[idx]);
}
else
{
double k0 = -(p1x-p0x)/(p1y - p0y);
double k1 = -(p2x-p0x)/(p2y - p0y);
double d0 = m0y - k0*m0x;
double d1 = m1y - k1*m1x;
double cx = (d0-d1)/(k1-k0);
double cy = cx*k0 + d0;
printf("cx = %lf,cy = %lf\n",cx,cy);
cirx[idx] = cx;
ciry[idx] = cy;
printf("cirx = %d,ciry = %d\n",cirx[idx],ciry[idx]);
}
}
void voronoi()
{
for(int i = 1; i <= trinum; i++)
{
if(!tri[i].use)
continue;
//printf("for %d near,%d,%d,%d\n",i,tri[i].near[0],tri[i].near[1],tri[i].near[2]);
calcir(tri[i].p[0],tri[i].p[1],tri[i].p[2],i);
if(cirx[i] > width)
cirx[i] = width*1.1;
if(cirx[i] < 0 )
cirx[i] = -width*0.1;
if(ciry[i] > height)
ciry[i] = height*1.1;
if(ciry[i] < 0 )
ciry[i] = -height*0.1;
drawbox(cirx[i],ciry[i],0,255,0);
}
bool mark[1000][1000];
memset(mark,0,sizeof(mark));
for(int i = 1; i <= trinum; i++)
{
if(!tri[i].use)
continue;
for(int j = 0; j < 3; j++)
{
int ne = tri[i].near[j];
if(ne == -1)
continue;
if(mark[i][ne] == 0)
{
printf("%d -- %d\n",i,ne);
mark[i][ne] = 1;
drawaLine(cirx[i],ciry[i],cirx[ne],ciry[ne],255,255,0);
}
}
}
}
int main(void)
{
possiondisk();
delaunay();
voronoi();
FILE* fp = fopen("rgba.png", "wb");
svpng(fp, 1024, 512, rgba, 1);
fclose(fp);
return 0;
}
/*
Copyright (C) 2017 Milo Yip. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
* Neither the name of pngout nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*! \file
\brief svpng() is a minimalistic C function for saving RGB/RGBA image into uncompressed PNG.
\author Milo Yip
\version 0.1.1
\copyright MIT license
\sa http://github.com/miloyip/svpng
*/
#ifndef SVPNG_INC_
#define SVPNG_INC_
/*! \def SVPNG_LINKAGE
\brief User customizable linkage for svpng() function.
By default this macro is empty.
User may define this macro as static for static linkage,
and/or inline in C99/C++, etc.
*/
#ifndef SVPNG_LINKAGE
#define SVPNG_LINKAGE
#endif
/*! \def SVPNG_OUTPUT
\brief User customizable output stream.
By default, it uses C file descriptor and fputc() to output bytes.
In C++, for example, user may use std::ostream or std::vector instead.
*/
#ifndef SVPNG_OUTPUT
#include <stdio.h>
#define SVPNG_OUTPUT FILE* fp
#endif
/*! \def SVPNG_PUT
\brief Write a byte
*/
#ifndef SVPNG_PUT
#define SVPNG_PUT(u) fputc(u, fp)
#endif
/*!
\brief Save a RGB/RGBA image in PNG format.
\param SVPNG_OUTPUT Output stream (by default using file descriptor).
\param w Width of the image. (<16383)
\param h Height of the image.
\param img Image pixel data in 24-bit RGB or 32-bit RGBA format.
\param alpha Whether the image contains alpha channel.
*/
SVPNG_LINKAGE void svpng(SVPNG_OUTPUT, unsigned w, unsigned h, const unsigned char* img, int alpha) {
static const unsigned t[] = { 0, 0x1db71064, 0x3b6e20c8, 0x26d930ac, 0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
/* CRC32 Table */ 0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c, 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c };
unsigned a = 1, b = 0, c, p = w * (alpha ? 4 : 3) + 1, x, y, i; /* ADLER-a, ADLER-b, CRC, pitch */
#define SVPNG_U8A(ua, l) for (i = 0; i < l; i++) SVPNG_PUT((ua)[i]);
#define SVPNG_U32(u) do { SVPNG_PUT((u) >> 24); SVPNG_PUT(((u) >> 16) & 255); SVPNG_PUT(((u) >> 8) & 255); SVPNG_PUT((u) & 255); } while(0)
#define SVPNG_U8C(u) do { SVPNG_PUT(u); c ^= (u); c = (c >> 4) ^ t[c & 15]; c = (c >> 4) ^ t[c & 15]; } while(0)
#define SVPNG_U8AC(ua, l) for (i = 0; i < l; i++) SVPNG_U8C((ua)[i])
#define SVPNG_U16LC(u) do { SVPNG_U8C((u) & 255); SVPNG_U8C(((u) >> 8) & 255); } while(0)
#define SVPNG_U32C(u) do { SVPNG_U8C((u) >> 24); SVPNG_U8C(((u) >> 16) & 255); SVPNG_U8C(((u) >> 8) & 255); SVPNG_U8C((u) & 255); } while(0)
#define SVPNG_U8ADLER(u) do { SVPNG_U8C(u); a = (a + (u)) % 65521; b = (b + a) % 65521; } while(0)
#define SVPNG_BEGIN(s, l) do { SVPNG_U32(l); c = ~0U; SVPNG_U8AC(s, 4); } while(0)
#define SVPNG_END() SVPNG_U32(~c)
SVPNG_U8A("\x89PNG\r\n\32\n", 8); /* Magic */
SVPNG_BEGIN("IHDR", 13); /* IHDR chunk { */
SVPNG_U32C(w); SVPNG_U32C(h); /* Width & Height (8 bytes) */
SVPNG_U8C(8); SVPNG_U8C(alpha ? 6 : 2); /* Depth=8, Color=True color with/without alpha (2 bytes) */
SVPNG_U8AC("\0\0\0", 3); /* Compression=Deflate, Filter=No, Interlace=No (3 bytes) */
SVPNG_END(); /* } */
SVPNG_BEGIN("IDAT", 2 + h * (5 + p) + 4); /* IDAT chunk { */
SVPNG_U8AC("\x78\1", 2); /* Deflate block begin (2 bytes) */
for (y = 0; y < h; y++) { /* Each horizontal line makes a block for simplicity */
SVPNG_U8C(y == h - 1); /* 1 for the last block, 0 for others (1 byte) */
SVPNG_U16LC(p); SVPNG_U16LC(~p); /* Size of block in little endian and its 1's complement (4 bytes) */
SVPNG_U8ADLER(0); /* No filter prefix (1 byte) */
for (x = 0; x < p - 1; x++, img++)
SVPNG_U8ADLER(*img); /* Image pixel data */
}
SVPNG_U32C((b << 16) | a); /* Deflate block end with adler (4 bytes) */
SVPNG_END(); /* } */
SVPNG_BEGIN("IEND", 0); SVPNG_END(); /* IEND chunk {} */
}
#endif /* SVPNG_INC_ */
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