how to get the pixel array from GLGraphicsOffScreen

mr.t

how to get the pixel array from GLGraphicsOffScreen

in Contributed Library Questions • 2 years ago

my goal is to get the pixel array from a GLGraphicsOffscreen Texture, to pass to a blob detection.

GLGraphicsOffscreen finalTexture;

within the draw loop:

   finalTexture.beginDraw();
   ....
   finalTexture.endDraw();

i try

finalTexture.loadPixels();

for (int i=0;i<finalTexture.pixels.length;i++){
         println(" pixel # " + i +" = " + finalTexture.pixels[i]);
}

and even though the offscreenImage is displayed correctly, the arry is completly black.

i also tryed to access it via

finalTexture.getTexture.pixels

with no luck.

Replies(9)

kooogy

Re: how to get the pixel array from GLGraphicsOffScreen

2 years ago

there's a loadTexture() method in the GlGraphics javadoc. details are scant but

http://glgraphics.sourceforge.net/reference/codeanticode/glgraphics/GLGraphicsOffScreen.html
" loadTexture() It copies the contents of the internal texture to both pixels arrays of the surface and the texture object."

and lots more on the GLTexture object.

bascially glGraphics has it's own version of loadPixels. this is bound to be slow - getting data off a graphics card always is but it does seem possible. very hard to tell from the one line descriptions what 'texture' actual means though, which one?

mr.t

Re: how to get the pixel array from GLGraphicsOffScreen

2 years ago

ah. nice. i did't spot that one!

but still no luck.
even though the description reads just right.
result is now a also visble black texture, and still nothing in the arry.

it seems to clear the texture. without copying anything.
or it copies it the wrong way, from the array to the texture..

kooogy

Re: how to get the pixel array from GLGraphicsOffScreen

2 years ago

this does, er, something. fills the PImage with the generated texture. am guessing you can getPixels from there...

import processing.opengl.*;
import codeanticode.glgraphics.*;
GLGraphicsOffScreen glg1;
PImage img;
void setup() {
size(100, 100, GLConstants.GLGRAPHICS);
img = new PImage(100, 100);
glg1 = new GLGraphicsOffScreen(this, 100, 100);
glg1.beginDraw();
// random ellipse in random colour
glg1.fill(230, 50, 20, random(50, 200));
glg1.ellipse(random(0, glg1.width), random(0, glg1.height), random(10, 50), random(10, 50));
glg1.endDraw();
// get texture from offscreen and place into img
glg1.getTexture().getImage(img);
}
void draw() {
// draw img
background(img);
noLoop();
}

kooogy

Re: Re: how to get the pixel array from GLGraphicsOffScreen

2 years ago

there are a bunch of methods on GlTexture like

public void getBuffer(int[] intArray)

which'll bypass the need for the PImage above, copy the data straight into a buffer, bytes or ints or whatever. should be faster too.

the source is supplied with the library so you just have a look through it.

mr.t

Re: how to get the pixel array from GLGraphicsOffScreen

2 years ago

thanx guys.

this solved it!

aufsess

Re: how to get the pixel array from GLGraphicsOffScreen

1 year ago

Is there a way to grab a single pixel from a GLTexture and avoid the performance slow down of having to use updateTexture() or loadTexture? I'm trying to implement a fast picker that uses GLGraphicsOffScreen to draw the picker buffer and this is the major bottleneck.

Thanks.

aufsess

Re: how to get the pixel array from GLGraphicsOffScreen

1 year ago

One way I've figured out how to do this is just make the GLGraphicsOffScreen lower rez, but I don't know how to set the renderer so it doesn't smooth out my mesh. I need it to be faceted and hard edged... any help on this?

mr.t

Re: how to get the pixel array from GLGraphicsOffScreen

1 year ago

Just acces it like described above.
Here is how you would use it.

This is super fast and no load / update Texture is needed.

int theArray = new int[texWidth * texHeight];
theTexture.getBuffer[theArray];

The only tricky part is that you now have to convert your 2Dimensional Position to an 1 Dimesional Array.

int myColorXY = theArray[Y*(texWidth)+X];

Best you make yourself a handy function like:

public int oneDee(int x, int y) {
return (y * width + x);
}
int myColorXY = theArray[oneDee(x,y)];

hope this helps a bit.

best.

mr.t

Re: how to get the pixel array from GLGraphicsOffScreen

1 year ago

I don't quite get how it smoothes the mesh!? maybe send a picture!

and ofcourse if you use GLoffscreen you need to acess the Texture first. Like:

theOffscreen.getTexture.getBuffer[theArray];

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