noise_captcha.pde

PGraphics imgNoise[],imgCaptcha,imgBlended;
int x1=0,x2=0,recorded=0;

void setup(){
  size(640,400);
  imgNoise=new PGraphics[2];
  for(int i=0;i<imgNoise.length;i++){
    imgNoise[i]=createGraphics(width,height);
    imgNoise[i].beginDraw();
    for(int y=0;y<height;y++){
      for(int x=0;x<width;x++){
        imgNoise[i].set(x,y,color(255*(int)random(2.0f)));
      }
    }
    imgNoise[i].endDraw();
  }
  imgCaptcha=createGraphics(width,height);
  imgCaptcha.beginDraw();
  imgCaptcha.background(0,0,0);
  imgCaptcha.textFont(createFont("微软雅黑 Bold",48.0f));
  imgCaptcha.scale(4.0f,4.0f);
  imgCaptcha.text(String.valueOf((int)random(1000.0f,10000.0f)),20.0f,70.0f);
  imgCaptcha.endDraw();
  imgBlended=createGraphics(width,height);
}

void draw(){
  blendMode(BLEND);
  image(imgCaptcha,0.0f,0.0f);
  blendMode(SCREEN);
  image(imgNoise[0],(float)x1,0.0f);
  image(imgNoise[0],(float)(x1-width),0.0f);
  x1=(x1+1)%width;
  imgBlended.beginDraw();
  imgBlended.blendMode(BLEND);
  imgBlended.image(imgCaptcha,0.0f,0.0f);
  imgBlended.blendMode(MULTIPLY);
  imgBlended.image(imgNoise[1],(float)x2,0.0f);
  imgBlended.image(imgNoise[1],(float)(x2-width),0.0f);
  x2=(x2+width-1)%width;
  imgBlended.endDraw();
  blendMode(SUBTRACT);
  image(imgBlended,0,0);
  if(recorded<2){
    saveFrame("f-##.png");
    recorded++;
  }
}