Little problem with an ArrayIndexOutOfBoundsException !

Programming Questions

mrenglet

Little problem with an ArrayIndexOutOfBoundsException !

in Programming Questions • 3 months ago

Hi,

I'm currently working on a way to make a book of an image, and in that way to write every hex color code of every pixel of the image in single PDF pages. My script work great but when I arrived to a certain value in my loop i got the super nice message ArrayIndexOutOfBoundsException. But i don't understand why ...

import processing.pdf.*;
PImage img;
PFont myFont;
int q ;
void setup() {
size(1000, 1000, PDF, "livre.pdf");
img = loadImage("img50.jpg");
}
void draw() {
background(255);
frameRate(30);
myFont = createFont("Monkey", 58);
textFont(myFont);
fill(0);
int pixel_long = (img.pixels).length;
println(pixel_long);
for (int i = 900; i<pixel_long;i=i+900) {
String [] pixel = str(img.pixels);
for (int k = 0;k<pixel_long;k=k+1) {
pixel[k] = hex(int(pixel[k]), 6);
}
String [] pixel_singlepage = subset(pixel, i-900, i);
println(pixel_singlepage);
String writing_pixel;
writing_pixel=join(sa3, " ");
textSize(18);
text(writing_pixel, 12, 0, width, height);
PGraphicsPDF pdf = (PGraphicsPDF) g;
pdf.nextPage();
}
println("finish");
noLoop();
exit();
}

PS : My ArrayIndexOutOfBoundsException problem is on the line 33 ...

Thanks for the one who reply !

Max

Replies(9)

tfguy44

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

Before we do anything else, please move lines 13, 14, 16, and 40 into setup().

mrenglet

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

Done !

PS : I found an error in line 39 in my first post, I forgot to change the name of the String. But that doesn't fix the first problem anyway ...

import processing.pdf.*;
PImage img;
PFont myFont;
int q ;
void setup() {
size(1000, 1000, PDF, "livre.pdf");
img = loadImage("img50.jpg");
frameRate(30);
myFont = createFont("Monkey", 58);
textFont(myFont);
textSize(18);
}
void draw() {
background(255);
fill(0);
int pixel_long = (img.pixels).length;
for (int i = 900; i<pixel_long;i=i+900) {
String [] pixel = str(img.pixels);
for (int k = 0;k<pixel_long;k=k+1) {
pixel[k] = hex(int(pixel[k]), 6);
}
String [] pixel_singlepage = subset(pixel, i-900, i);
String writing_pixel;
writing_pixel=join(pixel_singlepage, " ");
text(writing_pixel, 12, 0, width, height);
PGraphicsPDF pdf = (PGraphicsPDF) g;
pdf.nextPage();
}
println("finish");
noLoop();
exit();
}

tfguy44

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

I'm not sure what it is you're doing with the PDF, but here's some code to print the hex values of every pixel in an image.
It's looping correctly...

PImage img = loadImage("http://www.petersonbrothersqh.com/images/Img50.jpg");//"img50.jpg");
size(img.width, img.height);
image(img, 0, 0 );
img.loadPixels();
for (int i=0; i<img.pixels.length;i++) {
println( hex( img.pixels[i] ) );
}

benj.n.su..

Re: Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

+1 to using img.pixels.length directly in your for loop instead of:

int pixel_long = (img.pixels).length;

benj.n.su..

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

not having the image you are using, i can't be more helpful, however, if you are not familiar with what the error means, this short explanation will be of use:

http://wiki.processing.org/w/Why_do_I_get_an_ArrayIndexOutOfBoundsException%3F

short story: you are trying to manipulate an element in one of your arrays that is outside the length (bounds) of the array. for example, if the length of your array is 100 maybe you are trying to manipulate element 101, or element -1.

what the article reccomends, and is my go-to strategy as well, is to println the values of all variables related to the length of the arrays you are using. in your case, pixel_long, i, and k, and pixel.length, to make sure that i and k are always within the bounds of the arrays.

side note: does the length of pixel_long change such that you need to re-initialize it on each draw loop? if not, consider declaring it above and initializing it in your setup. else, it's just one factor to account for when debugging in your draw loop.

PhiLho

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

String [] pixel = str(img.pixels);
for (int k = 0;k<pixel_long;k=k+1) {
pixel[k] = hex(int(pixel[k]), 6);
}

So you convert the whole array of pixels to strings, then each string back to int to get the hex value? Not very efficient...

String [] pixel = new String[img.pixels.length];
for (int k = 0; k < img.pixels.length; k++) {
pixel[k] = hex(img.pixels[k]), 6);
}

Beside, as said, the error is probably dependent on the image you use.

mrenglet

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

Thanks all for your help,

First, in this example, my image is a 100x100 pixel random image, so normaly the img.pixels.lenght value is 10000.

But my loop bug when the "i" value > 5400, but still can't know why.

I know exactly what the ArrayIndexOutOfBoundsException is, so i don't understand, my loop must go on until 10000 ...

Btw, i changed the all hex conversion with your code PhiLho.

And I tried with an other image of an other amount of pixel, and its seems to work but now i've launch the script for a image of 1000x1000 pixel, so based of the script is gonna take 1000 pages of pdfs to write every pixel hex.

So i'm gonna wait and see.

Again thanks for you help !

PhiLho

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

Perhaps start your loop at zero.

mrenglet

Re: Little problem with an ArrayIndexOutOfBoundsException !

3 months ago

I didn't find the way to fix it, but now with the new image, the loop doesn't bug anymore ... so problem is kind of fix !

Thanks anyway for you help PhiLho !

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