Processing 1.0 - Processing Discourse - question about filters

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question about filters (Read 794 times)

Digi-D

question about filters
Feb 18^th, 2007, 4:07am

Hello have a question about the way filters are applied in Porcessing.
Here's the code.

void setup()
{
size(1000, 350);

PImage BaseImage, Image2Filter;

BaseImage=loadImage("shark.jpg");

Image2Filter=BaseImage; //copy all the pixels and start manipulating the copy,
//this way I think I will always have the original to go back to

Image2Filter.filter(GRAY); //apply filter to the image file
image(Image2Filter,0,0);

Image2Filter=BaseImage; //once again copy from the original

image(Image2Filter,500,0);

}

I assumed that I would get the filtered version next to the original but all i get are two filtered images. hmm... Can someone enlighten me as to what I am doing wrong here?

I am fairly new to processing so appologise if I am missing something basic.

thnx
d

Daniel Shiffman

Re: question about filters
Reply #1 - Feb 18^th, 2007, 2:24pm

In your code, you only ever create one PImage object (the loadImage() function "constructs" the PImage). Even though you have two variables -- BaseImage and Image2Filter -- when you set Image2Filter equal to BaseImage, what you are saying is "Both of these variables refer to the same Image object." This is *not* making a copy of the image. To do that you need to use the copy() function.

http://processing.org/reference/copy_.html

You could also just load the file twice as a quick solution:

Code:


PImage BaseImage, Image2Filter;  
// Make two distinct PImage objects!
BaseImage=loadImage("shark.jpg");
Image2Filter = loadImage("shark.jpg");   
	 
Image2Filter.filter(GRAY);
image(Image2Filter,0,0);    
image(BaseImage,500,0);

http://www.learningprocessing.com | http://www.shiffman.net | http://itp.nyu.edu

fry

Re: question about filters
Reply #2 - Feb 18^th, 2007, 3:12pm

to make a copy you actually use get(), ala:
baseImage=loadImage("shark.jpg");
image2Filter = baseImage.get();

get() with no parameters is simply the same as:
baseImage.get(0, 0, baseImage.width, baseImage.height).

which will produce a copy of the image. unfortunately, copy() only copies a section of the image, and doesn't create a new image.

Digi-D YaBB Newbies Offline Posts: 16	Re: question about filters Reply #3 - Feb 18^th, 2007, 7:29pm Thank you for the explanation. OO programming is still a bit of a mistery to me Will implement your suggestion. d

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