hi there
I have a code in which an image is read in terms of black or white. i then have a grid of crosses in which i would like the cross to be drawn if the initial pixel is white otherwise leave that space blank.
i have a code where i think this should be happening, but for some reason only a few crosses (when i believe there should be more) are being drawn.

can anyone help me please.
thanks

the code i have is;PImage snow;
void setup (){
background (255);
size (1200,1200);
snow =loadImage("snow.JPG");
image(snow, 0,0);
filter(GRAY);
filter(POSTERIZE, 2);
stroke (247,50,50);
fill (255);
}  
void draw ()
{  
   snow.loadPixels ();  
   for (int x = 15; x< snow.width; x+=30)  
   {  
  for (int y=15; y< snow.height; y+=30)  
  {  
 int i = (y * snow.width + x);  
 if (snow.pixels [i] == color(255) ) {  
 drawCross (x,y);
 }  
 else if (snow.pixels [i] == color(0) ) {  
 }  
  }  
   }  
}
void drawCross (int x, int y){
 line (x-5,y,x+5,y);
 line (x,y-5,x,y+5);


}

Hi, I hope this helps.
PS: There are more than one way of doing this.
The example below is just one of them
-----------------------------------------------------

PImage picture;
int value;

void setup() {
 picture = loadImage("snow.jpg");  //loads the image
 size (picture.width,picture.height); //sets the canvas size to the image size
 background(255);

 image(picture, 0,0); //loads the picture
 filter(GRAY); //greyscale
 filter(POSTERIZE, 2); //posterize  
 
 stroke(247,50,50); //sets stroke

 //loop trhough all the pixels on the screen
 for (int x=0; x < width; x++) {
   for (int y=0; y < height; y++) {
     //Since you only want black (rgb = 0,0,0) or white (rgb, 255, 255, 255), we only need to get one value of either the reds the greens or the blues.
    //This next line extracts the red value from the byte format that the function get returns
     value = get(x, y) >> 16 & 0xFF;
     if (r == 255) {
       //if it's white, then draw the cross
       drawCross (x, y);
     }
   }
 }
}

void draw() {
}

void drawCross (int x, int y){
 line (x-5,y,x+5,y);
 line (x,y-5,x,y+5);
}

Code:

...
 value = get(x, y) >> 16 & 0xFF; 
 if (r == 255) {
...
 

should be

Code:

...
int r = red( get(x, y) );  // read the amount of red from that pixel
if ( r == 255 ) {
...
 

right, that's just what it says:
you were asking for int (real numbers) but red gives float. you need to write ( .. i should have written):
float r = red( ...

Sorry about that.
It should be

if (value == 255) {

and not

if (r == 255) {

You're welcome!