pixels[] array help

Programming Questions

treebykoo..

in Programming Questions • 3 years ago

Hi,

I want to make a program that makes an array of every pixel from an image and then randomizes the array and reprints out the pixels. So for example you could make an abstract image from a normal .jpg....or even maybe rearrange and sort the pixels by color....go from there and do a bunch of stuff.

I'm trying to figure out exactly what the built in pixels[] array does. It says that the values of the array are of the color datatype. If i do something like println(myimage.pixels[400]); (just picking the 400th pixel at random here) I get a number that doesn't make sense to me like -9544132. If I try to assign a color variable to that pixel it doesn't work, i.e. color c = myimage.pixels[400]; Using the get(); function it works fine capturing a color. I know I'm way off base here...so what is that weird number? What can I do to get started writing this little program? I'm pretty sure I need to use the pixels[]; array...I just don't fully understand it.

Any help is much appreciated!!

Replies(10)

adam.ts

Re: pixels[] array help

3 years ago

calling pixels returns a 32 bit number with the first 8 bits alpha then red then green then blue

eg.

AAAAAAAARRRRRRRRGGGGGGGGBBBBBBBB

to pull each value out you can use a bit shift

http://processing.org/reference/rightshift.html

int col = pixels[x+y*width]

int red = (col>>16)&0xff //0xff equals 0000000000000000000000000000000011111111 therefore using & with it gives you the last 8 bits the color value of red from 0-255

int green = (col>>8)&0xff

int blue = (col)&0xff

I hope this helps

treebykoo..

Re: pixels[] array help

3 years ago

Hi,

Thanks so much for your help! This got me off to a great start. Below is my code for randomizing all the pixels in an image. When I run the program it looks like static from TV but I think that it's working. I guess I'm confused why the static is animated and doesn't just stop. Does my code look okay? Now my next challenge will be to sort out the colors.
Thanks again!

PImage meninas;

void setup() {

    meninas = loadImage("meninas.jpg");
    size(meninas.width,meninas.height);

}

void draw(){
meninas.loadPixels();

for (int y = 0; y < height; y++) {
for(int x = 0; x <width; x++) {

int col = meninas.pixels[y*width+x];
int r = (col >> 16)&0xff;

int g = (col >> 8) &0xff;

int b = (col)&0xff;

color newcolor = color(r,g,b);

fill(newcolor);

meninas.updatePixels();

      int ranx = int(random(width));
      int rany = int(random(height));
      set (ranx,rany,newcolor);
    }
}
}

adam.ts

Re: pixels[] array help

3 years ago

do you want each pixel of the old image to show only once in the new image?

ps. its animated because you put it in draw draw loops infinitley to stop this you can type noLoop(); in setup;

treebykoo..

Re: pixels[] array help

3 years ago

Hi,

Yeah...I just want each pixel in the old image to show only once in the new. I don't think this is happening. I figured that about the animation haha. Realized it right after I sent.

Thanks again for your help!!!

adam.ts

Re: pixels[] array help

3 years ago

then you want to use an array and shuffle it i would explain this more but i have to go to bed

treebykoo..

Re: pixels[] array help

3 years ago

Ha no problem. I really appreciate you taking the time to help me. I will google around about shuffling an array. Thanks!

treebykoo..

Re: pixels[] array help

3 years ago

Could anyone help me out how to do this? I was trying to make a function that shuffled the array...but I'm not even quite sure how to pass arrays into functions and also would I shuffle all three r,g,b arrays and then make a color with them and then use set(); to set the x,y coordinates? I was trying to implement this code ( http://processing.org/discourse/yabb2/YaBB.pl?num=1194572947) to shuffle my arrays...but it's a bit tricky with three for me. is that code good for this?

thanks for any help!!!

adam.ts

Re: pixels[] array help

3 years ago

link doesn't work i'll try to find a good shuffle function

adam.ts

Re: pixels[] array help

3 years ago

here you go this implements a shuffle called the fisher-yates shuffle

http://en.wikipedia.org/wiki/Fisher-Yates_shuffle

here is the code

it is a little confusing how the shuffle works but you can figure it out if you think about it long enough

PImage meninas;
void setup() {
meninas = loadImage("meninas.jpg");
size(meninas.width,meninas.height);
}
void draw(){
image(meninas,0,0);
}
void mouseClicked(){
image(meninas,0,0);
meninas.loadPixels();
for (int t=height*width;t>1;t--){
int rnd = int(random(t));//check from whats left
int h = meninas.pixels[rnd];
meninas.pixels[rnd]=meninas.pixels[t-1];//swap
meninas.pixels[t-1]=h;//shuffle
}
meninas.updatePixels();
}

this runs on click

treebykoo..

Re: pixels[] array help

3 years ago

Thank you so much! Wow that was much easier to do than I expected...thanks so much for your help!