Cycling 74 » Topic: Mgraphics not drawing stroke properly

Mgraphics not drawing stroke properly

Anthony Palomba — Mon, 10 Dec 2012 23:19:33 +0000

If you run the following code…

autowatch = 1;

var width = 500;
var height = 300;
var mgfx = new MGraphics(width,height);

mgfx.init();
mgfx.relative_coords = 0;
mgfx.autofill = 0;

var outmatrix = new JitterMatrix(4, “char”, width, height);

mgfx.redraw();

function bang()
{
draw();
}

function draw()
{
var theImage = null;

background(255);

mgfx.rectangle(0, 0, 100, 100);

mgfx.set_source_rgba(0, 0, 0, 1);
mgfx.stroke_preserve();

mgfx.set_source_rgba(0, 1, 1, 1);
mgfx.fill();

mgfx.identity_matrix();
theImage = new Image(mgfx.pop_group());
mgfx.image_surface_draw(theImage);

theImage.tonamedmatrix(outmatrix.name);
outlet(0, “jit_matrix”, outmatrix.name);

gc();

}

function clearBackground() {
background(0);
}

You will see that two sides of the border stroke are missing.
Did I get something wrong here?

-ap

Re: Mgraphics not drawing stroke properly

Anthony Palomba — Wed, 12 Dec 2012 16:53:35 +0000

Is this a bug or am I doing something wrong?

Re: Mgraphics not drawing stroke properly

Anthony Palomba — Fri, 14 Dec 2012 16:59:14 +0000

Anybody?

Re: Mgraphics not drawing stroke properly

Anthony Palomba — Mon, 17 Dec 2012 15:14:33 +0000

Surely someone here knows something about mgraphics.

Re: Mgraphics not drawing stroke properly

Frederic Dufeu — Mon, 17 Dec 2012 19:35:46 +0000

Hi Anthony,

Not sure about what you’re trying to achieve here but it sounds like you’d want to revert the stroke and fill operations:
// first
fill_preserve()
// then
stroke()

Best,
Frédéric

Re: Mgraphics not drawing stroke properly

Anthony Palomba — Mon, 17 Dec 2012 21:40:54 +0000

Let me rephrase my problem. My objective is to see a shape with a border around it.
The code I have now, draws the shape then the frame. What I should see is NOTHING.
The shape should cover the frame. What you actually see is a square with two sides
of the border.

If I reverse it, as you suggested, I see the frame but two of the sides are twice as thick.
I have included a test patch.

autowatch = 1;

var width = 500;
var height = 300;
var mgfx = new MGraphics(width,height);

mgfx.init();
mgfx.relative_coords = 0;
mgfx.autofill = 0;

var outmatrix = new JitterMatrix(4, “char”, width, height);

mgfx.redraw();

function bang()
{
draw();
}

function draw()
{
var theImage = null;

background(255);

mgfx.rectangle(0, 0, 100, 100);

mgfx.set_source_rgba(0, 1, 1, 1);
mgfx.fill_preserve();

mgfx.set_source_rgba(0, 0, 0, 1);
mgfx.stroke_preserve();

mgfx.identity_matrix();
theImage = new Image(mgfx.pop_group());
mgfx.image_surface_draw(theImage);

theImage.tonamedmatrix(outmatrix.name);
outlet(0, “jit_matrix”, outmatrix.name);

gc();

}

function clearBackground() {
background(0);
}

function background(rgb) {
with (mgfx)
{
set_source_rgb(rgb/255, rgb/255, rgb/255);
rectangle(0, 0, width, height);
fill();
}
}

– Pasted Max Patch, click to expand. –

Re: Mgraphics not drawing stroke properly

Frederic Dufeu — Mon, 17 Dec 2012 22:10:06 +0000

I believe your issue will be clearer if you don’t do the drawings at the upleft bounds of the jit.pwindow. See for instance what is happening when replacing mgfx.rectangle(0, 0, 100, 100) with mgfx.rectangle(10, 10, 100, 100).

In both cases you have to consider that stroke() has an irreducible thickness. Maybe try to experiment with function set_line_width(f) with f less than 1.

Hope that helps,

Best,
Frédéric

Re: Mgraphics not drawing stroke properly

Anthony Palomba — Mon, 17 Dec 2012 23:14:34 +0000

Ahhh you are right, starting at (0, 0) seems to clip the top and left side of the
border, which is why it is not seen. Thanks Frederic for helping me sort this out!