to mark edges on an blackwhite image ??

Programming Questions

cucuatdot..

to mark edges on an blackwhite image ??

in Programming Questions • 3 years ago

Hey guys , i've got a problem .
I just want mark the egdes on a random blackwhite picture and i have to work with a average value.
The problem is that i don't know the value so i cannot compare the current average value with the usual average value.

Here is the source :

PImage laa;

void setup () {
size (344,400);
laa = loadImage("xyz.jpg");
noLoop();
}

void draw(){
image(laa ,0 , 0);
for(int x=0; x<344; x++){
    for(int y=0; y<400; y++){
float mitte = blue(get(x,y));
float rechts = blue(get(x+1,y));
float links = blue(get(x-1,y));
float oben = blue(get(x,y+1));
float unten = blue(get(x,y-1));
float mw = (oben+unten+rechts+links+mitte)/5;
      color i = get(x,y);
float r = red(i);
float g = green(i);
float b = blue(i);
stroke(r,g,b);
point(x,y);

    }
}
}

so what I want is to mark the pixel if the average value of the pixel (with the neighbouringpixels ) is very different
than the usual average value .
How to do ?
please help me ! =)

Replies(3)

PhiLho

Re: to mark edges on an blackwhite image ??

3 years ago

Black & White or with gray levels? Apparently the latter, but it is a bit ambiguous...
Note: don't hard-code sizes in the code, use the width and height variables instead.
You probably need to do a first loop to average all the pixels of the image. Note that your method is very inefficient (ie. slow!), but at least it is easier to understand. We can give you hints to increase speed (use the pixels[] array) once your algorithm works.
Last note: prefer the Insert Code button to the Insert Quote one because the former offers an easy method to copy the code.

PhiLho

Re: to mark edges on an blackwhite image ??

3 years ago

Here is a sketch doing roughly what you describe (unless I misunderstood), but not doing what you expect (although it depends on what you call 'edges', and on the kind of image you want to use).

PImage laa;
float average;
void setup () {
size(270, 405);
laa = loadImage("xyz.jpg");
ComputeAverage();
noLoop();
}
void draw() {
println("Showing image");
image(laa, 0, 0);
if (mousePressed)
{
DrawEffect();
}
}
void mousePressed()
{
redraw();
}
void DrawEffect()
{
println("Image: " + laa.width + "x" + laa.height);
for (int x = 0; x < laa.width; x++) {
for (int y = 0; y < laa.height; y++) {
float mitte = blue(get(x, y));
float rechts = blue(get(x+1, y));
float links = blue(get(x-1, y));
float oben = blue(get(x, y+1));
float unten = blue(get(x, y-1));
float mw = (oben + unten + rechts + links + mitte) / 5;
color i = get(x, y);
float b = blue(i);
if (mw > average - 50 && mw < average + 50)
{
stroke(b, b, b);
}
else
{
stroke(255, 55, 55);
}
point(x, y);
}
}
// line(0, 0, width, height);
println("Done");
}
void ComputeAverage()
{
average = 0;
int pointNb = laa.width * laa.height;
for (int x = 0; x < laa.width; x++)
{
for (int y = 0; y < laa.height; y++)
{
average += blue(laa.get(x, y)) / pointNb;
}
}
println("Average: " + average);
}

cucuatdot..

Re: to mark edges on an blackwhite image ??

3 years ago

Hey thanks a lot . I've understood it , wow.

What i just notice is that used germand notations , but you did it great !

thanks , once again =)

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