Combining Multiple Imageswith Different Focus Depths

Presented by Steven Scher

sscher@ucsc.edu

UCSC, CS 290b, Fall 2005

Two Images of the same scenefocused at different depths

Focused Near Focused Far

Photos from Haeberli’s website

Divide Image into High-Frequency & Low-Frequency Components

Low-Frequency (Blurry)

High-Frequency (Edges)

Photos from Haeberli’s website

Quick Way:Blur Each Image for Low Frequencies

Subtract Low From Original for High Freq’s

blur

Original Low High

Original Low

Photos from Haeberli’s website

Finding Focus

• For Each Pixel in the Final Image– Compare the magnitude of each High-Frequency Component

– Take the original pixel value from the image whose High-Frequency Component was higher

Photos from Haeberli’s website

Finding Focus

Image 1 Image 2 Combination

Photos from Haeberli’s website

Advantage of Simple Algorithm:Short Code (Matlab)

• img_names = {‘near’,’far’};• filt = fspecial('gaussian',20,1); % Make blurring filter• for i = 1:length(img_names)• img_rgb{i} = imread(img_names{i}); % Read

Images• img_gray{i} = rgb2gray(img_rgb{i}); % Make

Gray• img_blurred = imfilter(img_gray{i}, filt); % Blur• img_edges(:,:,i)= abs(double(img_gray{i}) - double(img_blurred));• end• [temp, index] = max(img_edges,[],3); % Find biggest high-freq mag• best_gray = img_gray{1}; % Combine• for i = 2:length(img_gray)• best_gray(index==i) = img_gray{i}(index==i);• end

(My own code)

Example from Matlab Code

Focused Near Focused Far

(My own photos)

Combined Photo keeps some detail at both focus depths

(My own photos)

Focused NearFocused Far Combined

Papers to Look at

• A Multifocus Method for Controlling Depth of Field– Paul Haeberli– http://www.sgi.com/misc/grafic

a/depth/index.html

• Based on a previous paper– “Pyramid-based computer

graphics”– Ogden, Adelson, Berger, &

Burt– http://citeseer.csail.mit.edu/ad

elson84pyramid.html– Also discuss

interpolation/extrapolation, mosaicing,

Faces (old pictures)

Peter Burt James BergenEdward AdelsonJoan Ogden

Paul Haeberli