Resolution Reduction (Image Processing)

// Function for resolution reduction (useful for transforming/handling large images)
// Original code written by Peter Rehbein, Goethe-University, Frankfurt, Germany
Function Shrink(image, shrinkfactor)

Wave image
Variable shrinkfactor 

if(ShrinkFactor<=0)
	DoAlert /T="Alert" 0,"ShrinkFactor must be greater than 0!"
return -1
endif

Duplicate /O image adjusted_image
print "ShrinkFactor:"+num2str(shrinkfactor)
print "====="
Variable height = dimsize(adjusted_image,0)
Variable width = dimsize(adjusted_image,1)

print "Height (original):"+num2str(height)
print "Width (original):"+num2str(width)
print "====="
// Check whether image dimensions are dividable by shrink factor:

Variable check_height
Variable check_width

Variable new_height
Variable new_width

Variable u,v
Variable d,e

//Loop while height is not dividable by shrinkfactor and enlarge picture appropriately
//(New rows are filled with copied adjacent data)
check_height = mod(height,shrinkfactor)

if(check_height!=0)
print "Height not dividable by "+num2str(shrinkfactor)+"!"
	print "Starting correction!"
	print "====="
for(u=0;check_height!=0;u+=1)
	print "Actual Height: "+num2str(height)
	new_height = height+1
	Redimension/N=(new_height,-1) adjusted_image
		for(e=0;e<width;e+=1)
			//print "e: "+num2str(e)
			adjusted_image [new_height-1] [e] = adjusted_image [new_height-2] [e] 
		endfor
	height = new_height
	print "New Height: "+num2str(new_height)
	check_height = mod(height,shrinkfactor)
endfor
endif
// end check
	
//Loop while width is not dividable by shrinkfactor and enlarge picture appropriately
//(New columns are filled with copied adjacent data)
check_width = mod(width,shrinkfactor)
if(check_width!=0)
print "Width not dividable by "+num2str(shrinkfactor)+"!"
	print "Starting correction!"
	print "====="
for(v=0;check_width!=0;v+=1)
	print "Actual Width: "+num2str(width)
	new_width = width+1
	Redimension/N=(-1,new_width) adjusted_image
		for(d=0;d<height;d+=1)
			//print "d: "+num2str(d)
			adjusted_image [d] [new_width-1] = adjusted_image [d] [new_width-2] 
		endfor
	width = new_width
	print "New Width: "+num2str(new_width)
	check_width = mod(width,shrinkfactor)
endfor
endif
// end check

Variable sImage_Height = Height/ShrinkFactor
Variable sImage_Width = Width/ShrinkFactor
print "====="
print "SmallImage Height :"+num2str(sImage_Height)
print "SmallImage Width: "+num2str(sImage_Width)

Make /O /N=(sImage_Height, sImage_Width) sImage

Variable i,j,k,l

Variable avg

//print "====Report===="
for(i=0;i<sImage_Height;i+=1) //correct
	for(j=0;j<sImage_Width;j+=1) //correct		
	
		k=i*ShrinkFactor
		l=j*ShrinkFactor
				
		//print "===="
		//print "k:"+num2str(k)
		//print "l:"+num2str(l)
					
		Wave adjusted_image
		Duplicate/O/R=[k,k+ShrinkFactor-1][l,l+ShrinkFactor-1] adjusted_image,region // Extract region
		WaveStats /Q Region // Determine average pixel value
		avg = V_avg 
		//print "i: "+num2str(i)
		//print "j: "+num2str(j)
		//print "Average (region): "+num2str(avg)
		//print "i: "+num2str(i)
		//print "j: "+num2str(j)
		//print "===="
		sImage [i] [j] = avg // write average pixel value into smaller image	
	endfor
endfor

End