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my first sketch... (Read 689 times)
FinJim
my first sketch...
Nov 2nd, 2009, 2:00pm  
hello.
very new to the forum, first post, and i only downloaded processing over the weekend...the idea over the next year is to 'learn as i go' with processing with the end goal being a program that recognises different colours as inputs and outputs control data for a synth i've written in PureData. after the whole weekend i have a working program,below, but was wondering what i could've done better/more efficiently. as the end goal is real-time image processing, im trying to think about efficiency right from the very start.....and this is the very very start  :o

here is my first attempt:
-------------------------------------------------

void setup(){
 size(500,500);
 fill(12,324,54);
 //noLoop();
 PImage org = loadImage("squiggle500.png");
 image(org,0,0);
 PImage org2 = createImage(height,width,RGB);
 color clr2=color(255,0,0);
 color clr=color(0,0,0);

 loadPixels();
 for (int i = 0; i < height*width/2; i++)
 {

   if(red(pixels[i])>30)
   {
     pixels[i]=clr2;
   }
   else
   {
     pixels[i] = clr;
   }
 }
 updatePixels();
 org .get();
 save("proc.jpg");
}

void draw(){

 println(frameRate);
 PImage org2 = loadImage("proc.jpg");
 PImage org = loadImage("squiggle500.png");

 if (mousePressed && (mouseButton == LEFT)) {
   image(org2,0,0);
 }
 else{
   image(org,0,0);

 }
}
--------------------------------------------------------------------


any constructive criticism is very welcome,
thanks,
FJ
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PhiLho 
Re: my first sketch...
Reply #1 - Nov 2nd, 2009, 11:32pm  
Performance wise, using loadImag in draw is a no-no (unless carefully done in a conditional way, once, etc.): you load an image, ie. do disk access (unless system cache is kicking in) on each frame!

Little optimization hint: red() is a bit costly (not so much, but hey!), as it does a little more than doing bit shifting. So general advice is to do bit masking & shifting to get a color component.
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« Last Edit: Nov 3rd, 2009, 5:42am by PhiLho  »  
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FinJim
Re: my first sketch...
Reply #2 - Nov 3rd, 2009, 4:15am  
great, thanks for the heads up with red(), i've just had a look at the bit shift operations and conceptually red() is obviously easier to understand...but ive noted down the bit shift for later work.

as for the loadImag - i had thought this was the case, that it loads from disk on each interation. not good. if these are initiated in setup, could i then access them in draw? probably a very newbie question - as i assume the answer already is 'yes', but as of this afternoon i haven't been able to work out how to move these around.....?

thanks again for the input, its appreciated - especially at this stage of my learning curve!
FJ
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PhiLho 
Re: my first sketch...
Reply #3 - Nov 3rd, 2009, 5:44am  
The trick is to declare the PImage variables outside of any function: they are thus kind of global variables (actually, they are instance variables of the hidden class created by Processing) and can be accessed from any function.
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