Learning Tomography: Improving our BackProj script

A small post to see how the IJ script can be improved to avoid the stack of intermediate back-projections which is very memory consuming.




The only improvement comes from the last step (step #4) where the copy/paste is replaced by an addition between the rec2D and the temporary back-projection (image tmp).
Moreover, to avoid problem of number limitation (8-bit image allows numbers comprised between 0 and 255), the rec2D is defined as a 32-bit (floating point numbers).

The improved version of the backProj script is now ...

+++ IJ snippet +++

	// Simple back-projection technique
	// Jean-Christophe Taveau
	// http://crazybiocomputing.blogspot.com
	// 1- Get sinogram and create the final stack
	var imp = IJ.getImage();
	var w=imp.getWidth();
	var nbProj=imp.getHeight();
	var step=180/nbProj;
	var rec = IJ.createImage("Rec2D", "32-bit Black", w, w, 1);
	var ic = new ImageCalculator();
	// M a i n l o o p
	for (var y=0;y<nbProj;y++)
	{
	// 2- Extract a 1D-projection (one row of sinogram)
	imp.setRoi(0,y,imp.getWidth(), 1);
	var tmp = imp.duplicate();
	// 3- Do the backprojection and rotate accordingly
	IJ.run(tmp, "Size...", "width="+w+" height="+w+" average interpolation=None");
	IJ.run(tmp, "Rotate... ", "angle="+(-y * step)+" grid=1 interpolation=Bilinear fill");
	// 4- Add the rotated backprojection in the output image
	ic.run("Add",rec,tmp);
	tmp.close();
	}
	rec.show();

view raw gistfile1.js hosted with ❤ by GitHub

+++ End of IJ snippet +++

That's it today.

Other crazybiocomputing posts

Further readings are available in ...

• Learning Tomography Series  [Link]
• Image Processing TOC [Link]