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Index › Programming Questions & Help › Syntax Questions › Problematic Masking in Processing
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Problematic Masking in Processing (Read 2153 times)
Laani
Problematic Masking in Processing
May 27th, 2010, 8:19am  
Hi, I'm new to the processing community.

I have an issue with masking images, especially Black and white images. I'm masking one image with an Ellipse while displaying another image in the background. Here's the simplified code.

image(aut, 0, 0); //background image
ellipse(mouseX, mouseY, 300, 300);
loadPixels();
syd.mask(pixels);
image(syd, 0, 0, 1600, 900); // The image I'm masking

The mask works however I can still some image in the background where I shouldn't. This issue becomes worse when images are black and white. I'm guessing its something to do with the black and white values.

Does anyone have a solution to this issue?????

Also I'm using OPENGL if that causes extra complications

Thanks!
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PhiLho 
Re: Problematic Masking in Processing
Reply #1 - May 27th, 2010, 8:59am  
So, you draw an image, then you draw a big circle over it, and you use the whole to mask your off-screen image before copying it on the sketch, where the circle is. Right?
The problem is that you use the whole sketch's area as mask, so every pixel in is act as a mask, hence the phantom images...
You should use another off-screen PGraphics to draw the mask.
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Laani
Re: Problematic Masking in Processing
Reply #2 - May 27th, 2010, 9:05am  
I'm not sure that I'm following waht you mean by 'off-screen' ?
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blindfish
Re: Problematic Masking in Processing
Reply #3 - May 27th, 2010, 9:24am  
If my memory serves me well you can't have offscreen graphics with OpenGL; though I don't doubt that there are workarounds...
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Where is the what if the what is in why?
 
PhiLho 
Re: Problematic Masking in Processing
Reply #4 - May 27th, 2010, 2:22pm  
The mask doesn't have to be in OpenGL mode...
Just create a PGraphics, draw your ellipse in it, and use it as mask.
Off-screen means "not displayed", you draw in an image but user doesn't see it, he will see only the result.
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Laani
Re: Problematic Masking in Processing
Reply #5 - May 27th, 2010, 10:11pm  
I Think I may hae found a solution following both you pointers. (Thank you btw).

I'm now drawing the mask in a PGraphics object. This works however I have to use the P2D renderer. My program is running in OPENGL so there when I use the P2D is runs really slow.

I tried just running the whole program in P2D and the speed is ok but not as good as OPENGL.

does anyone know how to work around this issue? I'm just looking into PGraphicsOpenGL. Does anyone know if this is a better option?

Thanks!
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PhiLho 
Re: Problematic Masking in Processing
Reply #6 - May 28th, 2010, 1:08am  
I can be wrong because I have limited OpenGL experience, but I think you can create a mask in P2D/JAVA2D and use it in an OpenGL sketch.
That said, I guess it can still be slow, because when you do loadPixels Processing has to copy the data from the OpenGL buffer to a Java buffer.
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