Help with imwarp and affine2d

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thiirane
thiirane 2014-12-29
评论： DaltonTech 2020-4-12
Hello,
I have been trying to get imwarp to do a simple translation on an image but have been having some problems getting it to work. I have a reference image which I am using to rectify another image. I have the coordinate translations as x=-64 and y=-302. I have set up a coordinate transformation matix but the resulting image does not change.
figure(4);
xform=[1 0 0;0 1 0;64 302 1]; input_image='DSC08069.JPG';
f1=im2double(imread(input_image));
tform=affine2d(xform);
corr_RGBIM=imwarp(f1,tform);
imshow(corr_RGBIM);
title('RGB registered');
Any suggestions?

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采纳的回答

David Young
David Young 2014-12-29
The problem may be that imwarp() crops the output image to the transformed positions of the corners of the input image. A simple translation does not then have any effect. Try using imwarp_same(), attached, which applies the transformation and crops to the original positions of the corners.
  2 个评论
thiirane
thiirane 2014-12-29
Thank you David. That did the trick! I appreciate it.

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更多回答（3 个）

Image Analyst
Image Analyst 2014-12-29
编辑：Image Analyst 2014-12-30
Use the displacement field input argument of imwarp().
Try this to shift the image in x:
fontSize = 20;
grayImage = imread('cameraman.tif');
[rows, columns, numberOfColorChannels] = size(grayImage);
subplot(1, 2, 1);
imshow(grayImage);
axis on;
title('Original Image', 'fontSize', fontSize);
[rows, columns, numberOfColorChannels] = size(grayImage)
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
deltaX = 50; % Shift x by 50 pixels.
D = zeros(rows, columns,2);
D(:,:,1) = -deltaX; % Shift x by 50 pixels.
warpedImage = imwarp(grayImage, D);
subplot(1, 2, 2);
imshow(warpedImage);
axis on;
title('Shifted Image', 'fontSize', fontSize);
Try this to shift the image in x and y using the values of -64 and -302 like you specified:
fontSize = 20;
grayImage = imread('concordorthophoto.png');
[rows, columns, numberOfColorChannels] = size(grayImage);
subplot(1, 2, 1);
imshow(grayImage);
axis on;
title('Original Image', 'fontSize', fontSize);
[rows, columns, numberOfColorChannels] = size(grayImage)
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
deltaX = 64; % Shift x by 64 pixels.
deltaY = 302; % Shift y by 302pixels.
D = zeros(rows, columns, 2);
D(:,:,1) = -deltaX; % Shift x by 64 pixels.
D(:,:,2) = -deltaY; % Shift x by 302 pixels.
warpedImage = imwarp(grayImage, D);
subplot(1, 2, 2);
imshow(warpedImage);
axis on;
title('Shifted Image', 'fontSize', fontSize);
  3 个评论
显示 1更早的评论
Image Analyst
Image Analyst 2020-4-11
They now have an imtranslate() function that's much easier to use than imwarp().
DaltonTech
DaltonTech 2020-4-12
imtranslate looks nice, but 'translation' needs to be a 2-element vector. I need to translate the image using a displacement matrix because in my real problem I need to displace each pixel a different amount. Perhaps I need to modify imwarp to update the world limits so that the outer bounds of the output image are input+displacement value.

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k p
k p 2016-9-22
how to apply affine transform with euclidean distance to find shift between two image after finding matching point pair over image
Anas Musah
Anas Musah 2018-3-11
hello image analyst, I have tried ur code but it gives me this error
Not enough input arguments.
Error in imwarp (line 11)
cornerPoints = round(cornerPoints);
Error in untitled5 (line 41)
warpedImage = imwarp(grayImage, D);
pls any help

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