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Index › Programming Questions & Help › Syntax Questions › how to get previous x and y value
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how to get previous x and y value? (Read 1077 times)
katpet
how to get previous x and y value?
Jul 23rd, 2009, 3:17pm  
hi there,  I guess I have a beginner`s question.

Here is comes:

how to store the previous value (like to draw a line), if I use x and y values I get from a webcam.
I know pmouseX and pmouseY, is there an similar way to treat x and y without mouse?

Thanks a lot for helping!

kat
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seltar
Re: how to get previous x and y value?
Reply #1 - Jul 23rd, 2009, 11:41pm  
if you have a way to get x and y from a webcam, then this is an easy way to do what you want;

int pX, pY, x = 0, y = 0;

void draw()
{
 pX = x;
 pY = y;
 x = getXfromWebcam(); // make this function
 y = getYfromWebcam(); // make this function
}
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katpet
Re: how to get previous x and y value?
Reply #2 - Jul 27th, 2009, 12:00pm  
Thanks for advice!
Unfortunately I cannot make it work.
One coordinate of the line stays 0 /0.
Maybe too many definitions for x and y mixed up??
What I want is a line that follows the bright pixels.

This is the code I`m tinkering with:

import processing.video.*;

Capture video;
float valRed= 0;
float valGreen= 0;
float valBlue= 0;

int pX,pY, x =0, y=0;

void setup() {
 size(640, 480);
 background (0);
 
 video = new Capture(this, width, height, 30);
 stroke(15);
 smooth();
}

void draw() {
 valRed = random (255);
 valGreen = random (255);
 valBlue = random (255);
 
 pX = x;
 pY = y;
 
 if (video.available()) {
   video.read();
 
  int brightestX = 0;
  int brightestY = 0;
   float brightestValue = 0;
   video.loadPixels();
   int index = 0;
   for (int y = 0; y < video.height; y++) {
     for (int x = 0; x < video.width; x++) {
     
       int pixelValue = video.pixels[index];
   
       float pixelBrightness = brightness(pixelValue);
     

       if (pixelBrightness > brightestValue) {
         brightestValue = pixelBrightness;
         brightestY = y;
         brightestX = x;
       
       }
       index++;
     }
   }
 
 stroke(valRed, valGreen, valBlue);
  // rect(brightestX, brightestY, 20, 20);
   line (brightestX, brightestY, pX, pY);
 }
}


Can you tell me where the mistake is?
Thank you!

kat
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katpet
Re: how to get previous x and y value?
Reply #3 - Jul 27th, 2009, 12:19pm  
maybe this is a more simple sketch to show :

int pX, pY, x =50, y = 80;

float redValue = 0;
float greenValue = 0;
float blueValue = 0;

void setup () {
 size(400, 400);
 randomSeed (0);
 background(0);
 noStroke();
 
}


void draw() {
 
 redValue = random (255);
 greenValue = random (255);
 blueValue = random (255);
   fill (redValue, greenValue, blueValue);
 
 pX =x;
 pY = y;
 
 x+=random (-2, 2);
 y+=random(-2, 2);
 

 line(pX, pY, x, y);

}


But it is not working..


from
kat
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PhiLho 
Re: how to get previous x and y value?
Reply #4 - Jul 27th, 2009, 12:33pm  
I was perplex a few seconds. They I saw noStroke(), which is strange for a line() command. Then I saw you used fill() instead of stroke()...
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jaylfk
Re: how to get previous x and y value?
Reply #5 - Jul 27th, 2009, 9:20pm  
Try this.

Code:
import processing.video.*;

Capture video;
float valRed= 0;
float valGreen= 0;
float valBlue= 0;
int brightestX =0;
int brightestY =0;
int x = 0, y = 0, pX = 0, pY = 0;

void setup() {
 size(640, 480);
 background (0);
 
 video = new Capture(this, width, height, 30);
 stroke(15);
 smooth();
}

void draw() {
 valRed = random (255);
 valGreen = random (255);
 valBlue = random (255);
  
pX = brightestX;
pY = brightestY;

 if (video.available()) {
   video.read();
 
 
   float brightestValue = 0; 
   video.loadPixels();
   int index = 0;
   for (int y = 0; y < video.height; y++) {
     for (int x = 0; x < video.width; x++) {
     
	 int pixelValue = video.pixels[index];
    
	 float pixelBrightness = brightness(pixelValue);
     

	 if (pixelBrightness > brightestValue) {
	   brightestValue = pixelBrightness;
	   brightestY = y;
	   brightestX = x;
	  
	 }
	 index++;

     }
   }
 
 stroke(valRed, valGreen, valBlue);
  // rect(brightestX, brightestY, 20, 20);
   line (brightestX, brightestY, pX, pY);
 }
}


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katpet
Re: how to get previous x and y value?
Reply #6 - Jul 29th, 2009, 2:15am  
yes, that`s what I wanted! Thanks a lot!
It is the where and what in value declaration that troubles me.
Thanks again!

kat
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