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@Erkaman
Created December 31, 2016 11:50
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black-white-animation. Source code of this https://twitter.com/erkaman2/status/815151845068992512
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <vector>
#include <string>
using std::vector;
using std::string;
using std::to_string;
#define PI 3.14
const int WIDTH = 512;
const int HEIGHT = 512;
std::string zeroPad(int n, int len) {
string str = "";
str = to_string(n);
while(str.size() < len) {
str = "0" + str;
}
return str;
}
class vec2 {
public:
float x;
float y;
vec2(float x, float y) {
this->x = x;
this->y = y;
}
vec2() {
this->x = this->y = 0;
}
};
void makeSpiky(FILE* fp, float rad, string color) {
int N = 24;
// spiky center in image center.
float PX = WIDTH/2;
float PY = HEIGHT/2;
vector<vec2> pos(N);
float SMALLR = rad * 0.20f;
float LOL = rad * 0.05f;
const int NR = 8;
float rads[NR] = {
rad + SMALLR,
rad + SMALLR,
// rad + LOL,
rad - SMALLR,
rad - SMALLR,
// rad - LOL,
rad + SMALLR,
rad + SMALLR,
// rad + LOL,
rad - SMALLR,
rad - SMALLR,
// rad - LOL,
};
int ir = 0;
// generate points on circle. But displace the points in direction of normal.
// so that it becomes spiky.
for(int i = 0; i < N; i++) {
float theta = (i / (float)N) * 2.0 * PI;
float R = rads[ir];
ir = (ir + 1) % NR;
pos[i].x = PX + R * cos(theta);
pos[i].y = PY + R * sin(theta);
}
string str;
// now make line paths between the generated points.
for(int i = 0; i < (N+1); i++) {
vec2 v = pos[(i) % N];
if(i == 0) {
// for first point, we just position the cursor.
str += "<path d=\"M" + to_string(v.x) + ", " + to_string(v.y);
} else {
str += "L " + to_string(v.x) + " " + to_string(v.y) + " ";
}
}
str += "Z\n"; // close loop. path is now done.
str += "\" />";
float strokeWidth = 2.0f + 10.0f * (rad / 100.0f);
if(strokeWidth > 4.0f) { // clamp stroke-width to max 8.0f
strokeWidth = 4.0f;
}
fprintf(fp,"<g fill=\"white\" stroke=\"black\" stroke-width=\"%f\" fill-opacity=\"1.0\">", strokeWidth);
fprintf(fp,"%s", str.c_str() );
fprintf(fp,"</g>");
}
struct Star {
float rad;
string color;
Star(float rad, string color) {
this->rad = rad;
this->color = color;
}
};
int main(int argc, char** argv) {
// create output dir.
system("mkdir -p temp/");
float START_RAD = 3.0f;
float SPAWN_RAD = 40.0f;
float VEL = 2.0f;
// colors of spikys.
const int NC = 3;
string colors[NC] = {
/* "#990022",
"#888822",
"#9C8066",
*/
"#FFFFFF",
"#FFFFFF",
"#FFFFFF"
};
int frames = NC * (ceil( (SPAWN_RAD - START_RAD)/VEL ));
printf("frames: %d\n", frames);
int ic = 0;
string curColor = colors[ic];
vector<Star> stars;
stars.push_back(Star(START_RAD, curColor));
for(int i = 0; i < 300; i++) { // 1000
FILE* fp = fopen(("temp/out" + zeroPad(i, 5) + ".svg").c_str(), "w");
fprintf(fp, "<svg width=\"%f\" height=\"%f\" version=\"1.1\" baseProfile=\"full\" xmlns=\"http://www.w3.org/2000/svg\">\n", (float)WIDTH, (float)HEIGHT);
// clear to black background.
fprintf(fp,"<rect ");
fprintf(fp,"width=\"%d\" ", WIDTH);
fprintf(fp,"height=\"%d\" ", HEIGHT);
fprintf(fp,"x=\"0\" ");
fprintf(fp,"y=\"0\" ");
fprintf(fp,"fill=\"#FFFFFF\"/>\n");
for(int j = 0; j < stars.size(); j++) {
Star& star = stars[j];
makeSpiky(fp, star.rad, star.color);
star.rad+=VEL; // spiky velocity.
}
// once last spiky is big enough, spawn another one.
const float& lastRad = stars[stars.size()-1].rad;
if(lastRad > SPAWN_RAD) {
ic = (ic+1)%NC;
curColor = colors[ic];
stars.push_back(Star(START_RAD, curColor));
}
fprintf(fp, "</svg>");
fclose(fp);
}
printf("created svgs\n");
// system("cd temp/ && for i in out00257.svg; do rsvg-convert $i -o `echo $i | sed -e 's/svg$/png/'`; done && open out00257.png");
system("cd temp/ && for i in *.svg; do rsvg-convert $i -o `echo $i | sed -e 's/svg$/png/'`; done");
printf("converted svgs to png\n");
// frames from (225) to (225+58) makes a good loop.
system("cd temp/ && ffmpeg -start_number 225 -y -framerate 30 -i out%05d.png -vframes 58 -c:v libx264 -vf \"scale=512:512\" -r 30 ../out.mp4 ");
printf("encoded to mp4\n");
return 0;
}
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