Image always appearing as empty

faizinator

I've been trying to get the degree of redness in an RGB image and show it in another image. But the destination image always appears empty. I'm pretty much a newb at processing. here's my code.

//code to get Degree of Redness
import processing.video.*;
Capture cam; 
PImage img,imDeg,imThresh;
void setup()
 {
  imDeg=createImage(320,240,GRAY);
  imThresh=createImage(320,240,GRAY);
  size(640, 480);
  String [] cameras=cam.list();
  cam = new Capture(this,320,240,cameras[0]);
  cam.start(); 
} 

void DegreeRed()
{
  img.loadPixels();
  imDeg.loadPixels();
  for(int x=0;x<320;x++)
  {
    for(int y=0;y<240;y++)
    {

      //location of pixel
      int loc=x*240+y;

      //get RGB values
      float r1=red(img.pixels[loc]);
      float g1=green(img.pixels[loc]);
      float b1=blue(img.pixels[loc]);

      //Degree of Redness
      float r=r1-(g1+b1);
      float g=r1-g1;
      float b=r1-b1;
      if(r<0) r=0;
      if(g<0) g=0;
      if(b<0) b=0;
      float Dr=r+g+b;
      imDeg.pixels[loc]=int(Dr);
    }
  }
  imDeg.updatePixels();
}

void draw() 
{
  scale(2);
  if (cam.available()) { 
    // Reads the new frame
    cam.read(); 
  }
  img=cam;
  DegreeRed();
  //Thresh();
  image(imDeg, 0, 0); 
}

I'm continuously taking images from a camera and passing it through this function and printing the resulting imDeg image on the screen. But the image always appears empty. Thank You for your help.

GoToLoop

http://forum.processing.org/two/discussion/8045/how-to-format-code-and-text

faizinator

thanx for informing about the format

GoToLoop

I believe your RGB algorithm isn't working right.
You better search the forum for how to do it correctly.
Better read about alternative approaches for RGB extraction and reinsertion:

1. https://processing.org/reference/red_.html
2. https://processing.org/reference/green_.html
3. https://processing.org/reference/blue_.html

And although not exactly you're looking for, here's an example of getting RGB from color:
http://forum.processing.org/two/discussion/4461/pimage-color-format

faizinator

I'm sorry but I don't understand. I think I have used those red,green and blue functions correctly. When i print out the RGB values, it works. Is it perhaps reinsertion in the GRAY image object(imDeg) that is causing the problem?

GoToLoop

Indeed float Dr=r+g+b; doesn't seem right to me.
It needs bitshifting in order to place each primary color in its right place within the color!
Also, you shouldn't be using float while dealing w/ RGB either!

faizinator

But since i declared the image as GRAY, shouldn't it be a single dimensioned colour rather than it having RGBs? Also, the red,blue,green functions return a floating point value. I am converting it to int when assigning it back imDeg.pixels[loc]=int(Dr); . So what should i do if i want a grayscale image? Is it perhaps assigning the same value to all three of RGB?

GoToLoop

Gray scale happens when all RGB channels are similar to each other.
Preferably, when R = G = B! :-B

Volpi

For a gray image you indeed want the same value for all RGB, but if you just add them together you'll have a number above 255 and that won't be of much use. To get a gray color with the right value you must average the RGB colors, that is, grayColor = (r + g + b)/3.

faizinator

Thanx for your help

GoToLoop

Just an extra addendum. This article explains better what a color is in Processing: ;)

http://forum.processing.org/two/discussion/8086/what-is-a-color-in-processing