MATLAB: How use formula for image vignetting

Image Processing Toolboxshadingvignetting

I want use this code for image vignnetting

i=imread('flower.jpg')
im=double(i)
[x,y,z]=size(im);
c=im(round(x/2),round(y/2));
%pix_1 = [p11,p12];
%pix_2 = [p21,p22];
%distance = sqrt( (p21-p11)^2 + (p22-p12)^2 );
distane=sqrt((x1-cx)^2 + (y1 - cy)^2)
x1,y1 ar cx, cy er distance - sqrt((x1-cx)^2 + (y1 - cy)^2);

Best Answer

Lots wrong with that, starting with this:

[x,y,z]=size(im);

The size function does not return the size of the image in that order. It returns the size in the order [y, x, z] because it returns [rows, columns, slices]. Plus if you don't ask for the third dimension (you did but many others don't), you're in trouble. See this link for more info: Steve Eddin's blog about the size function

Try this corrected code:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 18;
fprintf('Beginning to run %s.m ...\n', mfilename);
% Original, bad code from original poster.
% i=imread('flower.jpg')
% im=double(i)
% [x,y,z]=size(im);
% c=im(round(x/2),round(y/2));
% %pix_1 = [p11,p12];
% %pix_2 = [p21,p22];
% %distance = sqrt( (p21-p11)^2 + (p22-p12)^2 );
% distane=sqrt((x1-cx)^2 + (y1 - cy)^2)
% x1,y1 ar cx, cy er distance - sqrt((x1-cx)^2 + (y1 - cy)^2);
%   0 Comments
% Corrected code:
rgbImage = imread('flower.jpg');
rgbImage = imread('peppers.png');
[rows, columns, numberOfColorChannels] = size(rgbImage)
subplot(2, 2, 1);
imshow(rgbImage);
impixelinfo;
title('Original Color Image', 'FontSize', 20);
axis('on', 'image');
% Get vignetting pattern (not really, this is not the right formula, but let's just pretend this function is it).
[x, y] = meshgrid(1:columns, 1:rows);
distanceImage = sqrt((x-columns/2).^2 + (y - rows/2).^2);
% Normalize to a percentage so it's in the 0-1 range:
distanceImage = 1 - distanceImage / max(distanceImage(:));
% Get a profile through the middle and plot it.
yMid = int32(rows/2);
horizontalProfile = distanceImage(yMid, :);
subplot(2, 2, 3);
plot(horizontalProfile, 'b-', 'LineWidth', 2);
title('Horizontal Profile', 'FontSize', 20);
xlabel('Column', 'FontSize', 20);
ylabel('Attenuation Factor', 'FontSize', 20);
grid on;
% Convert to color
if numberOfColorChannels == 3
	distanceImage = cat(3, distanceImage, distanceImage, distanceImage);
end
subplot(2, 2, 2);
imshow(distanceImage, []);
yline(yMid, 'Color', 'b', 'LineWidth', 2);
impixelinfo;
axis('on', 'image');
title('Distance Image', 'FontSize', 20);
% Multiply the images together.
outputImage = uint8(distanceImage .* double(rgbImage));
subplot(2, 2, 4);
imshow(outputImage, []);
axis('on', 'image');
title('Output Image', 'FontSize', 20);
impixelinfo;

By the way, that's not a true optical vignetting function. Actually it will be much flatter in the middle and fall off much more sharply at the edge if the aperture gets in the way, or if the aperture is not in the way (and you have just general/typical lens shading), it will be much flatter - it won't fall off to zero.

Related Solutions

MATLAB: Crop dark area and display the face only

Convert to grayscale and then threshold and find the bounding box

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
% Read in the color image.
folder = pwd;
baseFileName = 'm2.bmp';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
  % Didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
rgbImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 3.
[rows, columns, numberOfColorBands] = size(rgbImage);
% Display the original color image.
subplot(2, 3, 1);
imshow(rgbImage, []);
axis on;
title('Original Color Image', 'FontSize', fontSize);
drawnow;
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Histogram the red channel, but there is a huge spike at 255 so let's not count those.
subplot(2, 3, 2);
grayImage = rgb2gray(rgbImage);
imshow(grayImage, []);
title('Gray Scale version', 'FontSize', fontSize);
subplot(2, 3, 3);
histogram(grayImage(grayImage<255))
grid on;
title('Histogram of Gray Scale Image', 'FontSize', fontSize);
someThresholdValue = 150;
binaryImage = grayImage > someThresholdValue;
% Take largest blob
binaryImage = bwareafilt(binaryImage, 1);
subplot(2, 3, 4);
imshow(binaryImage);
grid on;
title('Binary Image', 'FontSize', fontSize);
% Label the binary image.
labeledImage = bwlabel(binaryImage);
props = regionprops(labeledImage, 'BoundingBox');
bbox = props.BoundingBox
croppedImageRGB = imcrop(rgbImage, bbox);
subplot(2, 3, 5);
imshow(croppedImageRGB);
grid on;
title('Cropped RGB Image', 'FontSize', fontSize);
% Gray scale version of cropped image
croppedImageGray = imcrop(grayImage, bbox);
subplot(2, 3, 6);
imshow(croppedImageGray);
grid on;
title('Cropped Gray Scale Image', 'FontSize', fontSize);

MATLAB: How to find the height and width of an object

Try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 25;
%===============================================================================
% Get the name of the first image the user wants to use.
baseFileName = 'A.jpg';
folder = fileparts(which(baseFileName)); % Determine where demo folder is (works with all versions).
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % The file doesn't exist -- didn't find it there in that folder.
  % Check the entire search path (other folders) for the file by stripping off the folder.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
%=======================================================================================

% Read in demo image.
rgbImage = imread(fullFileName);
% Get the dimensions of the image.
[rows, columns, numberOfColorChannels] = size(rgbImage);
% Display the original image.

subplot(2, 2, 1);
imshow(rgbImage, []);
axis on;
caption = sprintf('Original Color Image, %s', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0.05 1 0.95]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
[rows, columns, numberOfColorChannels] = size(rgbImage)
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
%   grayImage = rgb2gray(rgbImage);
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  grayImage = rgbImage(:, :, 1); % Take red channel.
end
% Display the image.
subplot(2, 2, 2);
imshow(grayImage, []);
axis on;
caption = sprintf('Gray Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo();
drawnow;
% Display the histogram of the image.
subplot(2, 2, 3);
histogram(grayImage, 256);
caption = sprintf('Histogram of Gray Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
grid on;
drawnow;
%=======================================================================================
binaryImage = grayImage < 150;
% Keep only the largest blob.
binaryImage = bwareafilt(binaryImage, 1);
% Display the masked image.
subplot(2, 2, 3);
imshow(binaryImage, []);
axis on;
caption = sprintf('Binary Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo();
drawnow;
% Get the bounding box of the blob.
props = regionprops(binaryImage, 'BoundingBox');
boundingBox = [props.BoundingBox]
% Display the original image.
subplot(2, 2, 4);
imshow(rgbImage, []);
axis on;
caption = sprintf('Original Color Image, %s', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
% Plot the bounding box over it.
hold on;
rectangle('Position', boundingBox, 'LineWidth', 2, 'EdgeColor', 'r')

Best Answer

Related Solutions

MATLAB: Crop dark area and display the face only

MATLAB: How to find the height and width of an object

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