Redraw to draw around something

Programming Questions

the.engin..

Redraw to draw around something

in Programming Questions • 6 months ago

Hi! As a beginner I stucked at my test code, however it's quite simple. Here it is:

int a =0;
int b = 0;
int c = 0;
int d = 0;
void setup()
{
size(500,500);
}
void draw()
{
background(255);
line(c,d,a,b);
}
void mouseMoved()
{
a = mouseX;
b = mouseY;
}
void mouseClicked()
{
c = a;
d = b;
}

I would like to mark points on a picture, without processing redraw the already marked points and the lines between these points. I've tried the redraw function to, but did not solved my problem.

Could you help me with this issue?

Thanks!

Andrew

Replies(6)

v.k.

Re: Redraw to draw around something

6 months ago

Maybe just don't call background() at beginning of draw() ...

the.engin..

Re: Redraw to draw around something

6 months ago

My first post was not complete. In my code, I would like to mark points with the mouseClicked() function, but when I just move the mouse, I want to see only the one line, that follows the mouse. Then I click at a point, my program marks the point at (mouseX,mouseY) and a new line from this point follows my mouse again...

But if I remove background() from the draw function, processing leave the previously drawed lines on the screen.

GoToLoop

Re: Redraw to draw around something

6 months ago

You have to create another layer to draw those temporary lines. That is, a PGraphics instance.
This way, you can draw upon this new layer w/o modifying the "main" layer.

P.S.: Make the extra PGraphics w/ transparent background!

quarks

Re: Redraw to draw around something

6 months ago

In my code, I would like to mark points with the mouseClicked() function, but when I just move the mouse, I want to see only the one line, that follows the mouse. Then I click at a point, my program marks the point at (mouseX,mouseY) and a new line from this point follows my mouse again..

It is not clear what you want to happen because the code you posted appears to do what you want. The only line you can see is from the last point clicked to the mouse position.

quarks

Re: Redraw to draw around something

6 months ago

From the title of this topic it seems that you might want to draw a shape defined by a series of mouse clicks. If that is the case then this code might help. Try running it and let us know if this is want you need.

ArrayList<PVector> points;
void setup() {
size(500, 500);
points = new ArrayList<PVector>();
}
void draw() {
background(255);
if (points.size() > 0) {
PVector pa = points.get(0);
PVector pb;
if (points.size() > 1) {
for (int i = 1; i < points.size(); i++) {
pb= points.get(i);
line(pa.x, pa.y, pb.x, pb.y);
pa = pb;
}
}
line(pa.x, pa.y, mouseX, mouseY);
}
}
void mouseClicked() {
points.add(new PVector(mouseX, mouseY));
}

the.engin..

Re: Re: Redraw to draw around something

6 months ago

OMG! That is the same thing that I want!

Thanks for your help!

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