Fast way to manipulate each pixel from ImagePlus

Question

Hello I need to access every pixels of an ImagePlus for image analysis.

Because of the huge amount of images to process, I was wondering if there are special effective ways/methods to access and/or modify each pixel from an imagePlus? The only idea I naturally come out with is double for-looping through the image matrix, which takes me several dozens of seconds to achieve on a 1000x1000 image. Here is my code:

ImagePlus Iorg = IJ.openImage("Demo1.png");
int[] pix = Iorg.getPixel(5, 5);
if(Iorg.getSlice() != 1) {
    System.exit(0);
}

for(int w=0; w< Iorg.getDimensions()[0]; w++) {
    for(int h=0; h<Iorg.getDimensions()[1]; h++) {
       System.out.println(w + " x " + h);
       // DO what needs to be done      
    }
}

Any idea?

1) `System.out.print` will take so much time. 2. Try to use library methods rather than for loops. 3) What are you trying to do inside `DO what needs to be done`? — smttsp, Apr 17 '14 at 13:39
For now I would like to divide every pixel by the maximum intensity, which is 255. Indeed I removed System.out.print and it now takes 1 second to loop through the whole matrix :P — kaligne, Apr 17 '14 at 14:08
For division you could use `Iorg.getProcessor().multiply()` to do the math without looping. I think you better have the image be 32bit float before doing this. — Kota, Apr 17 '14 at 14:21

score 0 · Answer 1 · answered Apr 17 '14 at 19:15

Since images are uchar, what you want to do is the equivalent of

if(selected_pixel==255) 
     selected_pixel = 1; 
else 
     selected_pixel = 0

You can create mask, that would be easier. I don't know in java ImagePlus but in matlab it is mask = image==255;.

Try to use those kind of matrix operations according to your need. I'm sure these methods should be somewhere inside the library(if ImagePlus is image processing library.)

Fast way to manipulate each pixel from ImagePlus

1 Answers1