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Resolution Reduction (Image Processing)
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PeterR
// 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
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June 5, 2014 at 12:12 pm - Permalink
you could exchange
V_avg
forV_min
orV_max
and write these values to the shrunken image instead :)(This is actually what I wrote the snippet for)
Besides, it was fun to code ^^
June 6, 2014 at 12:13 pm - Permalink
it is usually a good idea to avoid memory allocations. Your code uses Duplicate followed by WaveStats. You could skip the Duplicate completely if you used ImageStats instead of WaveStats. Also, using either WaveStats or ImageStats you should be able to see some performance improvement with a /M=1 flag.
A.G.
June 6, 2014 at 12:27 pm - Permalink
June 6, 2014 at 12:31 pm - Permalink