Hi,

we just managed to make a video out of sketch animation using saveFrame() function. Now we want to make a video with transparent background but we can't export even a single picture with transparent background. we tried using class createGraphics() but without luck. we are new to Processing and programming in general so a dummy help would be very welcome. Here is the code based on the example from Ira Greenberg's book:

/*
title: bouncing balls
description: balls deflect off sketch window edges
created: August 9, 2005
by: Ira Greenberg
*/
// global variables
int ballCount = 500;
int ballSize = 8;
int ballSpeed = 3;
float[]xspeed = new float[ballCount];
float[]yspeed= new float[ballCount];
float[]xpos = new float[ballCount];
float[]ypos = new float[ballCount];
float[]wdth = new float[ballCount];
float[]ht = new float[ballCount];

//initialize sketch
void setup(){
 //set sketch window size and background color
 smooth();
 size(400, 400);
 background(0);
 
 //initialize values for all balls
 for (int i= 0; i< ballCount; i++){

   // set varied ball speed
   xspeed[i] = random(1, ballSpeed);
   yspeed[i] = random(-ballSpeed, ballSpeed);

   // ball varied ball sizes
   wdth[i]= random(1, ballSize);
   ht[i]= wdth[i];

   // set initial ball placement
   xpos[i] = width/2+random(-width/3,  width/3);
   ypos[i] = height/2+random(-height/3,  height/3);
 }


 // turn off shape stroke rendering
 noStroke();
 //set the animation loop speed
 frameRate(30);
}

// begin animation loop
void draw(){

 /*updates background
  comment out to use alternate
  fill option below*/
 background(0);

 for (int i=0; i<ballCount; i++){

   /*To use this fill option:
    1. uncomment fill call below
    2. comment out the background
    function call above*/
   fill(i*255/ballCount, i*100/ballCount, i*170/ballCount);

   //draw balls
   ellipse(xpos[i], ypos[i], wdth[i], ht[i]);

   //upgrade position values
   xpos[i]+=xspeed[i];
   ypos[i]+=yspeed[i];

   /*conditionals:
    detects ball collision with sketch window edges
    accounting for ball thickness.
    */
   if (xpos[i]+wdth[i]/2>=width || xpos[i]<=wdth[i]/2){
     xspeed[i]*=-1;
   }
   if (ypos[i]+ht[i]/2>=height || ypos[i]<=ht[i]/2){
     yspeed[i]*=-1;
   }
 }
}

We would like to export this as a video with transparent background (=set of images with transparent background) so if anyone could fix our code or explain where/how to use createGraphics() we would be very very grateful.

Thank you very much,
kind regards,
Midva:*