Help with imwarp and affine2d

Question

thiirane 2014-12-29

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/168461-help-with-imwarp-and-affine2d

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?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

David Young 2014-12-29

7
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/168461-help-with-imwarp-and-affine2d#answer_163601

imwarp_same.m

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
显示无隐藏无

thiirane 2014-12-29

Thank you David. That did the trick! I appreciate it.

Daoyu Li 2019-10-9

nice work！

请先登录，再进行评论。

Answer 2

Image Analyst 2014-12-29

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/168461-help-with-imwarp-and-affine2d#answer_163603

编辑：Image Analyst 2014-12-30

在 MATLAB Online 中打开

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更早的评论隐藏 1更早的评论

DaltonTech 2020-4-11

在 MATLAB Online 中打开

Hi all,

I am trying to shift an image with imwarp using the displacement option. However I would like to shift the image inside an array slightly bigger than the image, without cropping the image during shifting. Below is a modified version of Image Analyst's code to demonstrate my problem. First I pad grayImage with mean grey level values, then I pad the displacement vector with zeros by the same amount. The subplot shows the result, where unfortunately the right hand side of the image is missing.

clear all
fontSize = 20;
grayImage = imread('cameraman.tif');
imshow(grayImage)
[rows, columns, numberOfColorChannels] = size(grayImage);
subplot(2, 2, 1);
imshow(grayImage);
axis on;
title('Original Image', 'fontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Displacement matrix
deltaX = 50; % Shift x by 50 pixels.
D = zeros(rows, columns,2);
D(:,:,1) = -deltaX; % Shift x by 50 pixels.
% Warp the original image
warpedImage = imwarp(grayImage, D);
subplot(2, 2, 2);
imshow(warpedImage);
axis on;
title('Shifted Image', 'fontSize', fontSize);
%--------------------------------------------------------------------------
% Additions
%--------------------------------------------------------------------------
% Average grey level of image
meanGreyLevel =  round(mean(grayImage(:)));
% Amount of pixels to pad image
colsPad = 20;
rowsPad = 10;
% Pad option
colPadOption = 'post';
rowPadOption = 'both';
% Pad the columns
tempImage = padarray(grayImage, [0 colsPad], meanGreyLevel, colPadOption);
% Pad the rows
grayImagePadded = padarray(tempImage, [rowsPad 0], meanGreyLevel, rowPadOption);
% Show the image
subplot(2, 2, 3);
imshow(grayImagePadded);
axis on;
title('Padded Image', 'fontSize', fontSize);
% Pad the displacement matrix with 0's to match the padded image
% Pad the columns
tempDisp = padarray(D, [0 colsPad], 0.0, colPadOption);
% Pad the rows
DPadded = padarray(tempDisp, [rowsPad 0], 0.0, rowPadOption);
% Warp the padded image (fill displaced space with avg. grey level)
warpedPaddedImage = imwarp(grayImagePadded, DPadded, 'FillValues', meanGreyLevel);
subplot(2, 2, 4);
imshow(warpedPaddedImage);
axis on;
title('Shifted Padded Image', 'fontSize', fontSize);

Thanks in advance.

Image Analyst 2020-4-11

They now have an imtranslate() function that's much easier to use than imwarp().

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.

请先登录，再进行评论。

Answer 3

k p 2016-9-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/168461-help-with-imwarp-and-affine2d#answer_235662

how to apply affine transform with euclidean distance to find shift between two image after finding matching point pair over image

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 4

Anas Musah 2018-3-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/168461-help-with-imwarp-and-affine2d#answer_309497

在 MATLAB Online 中打开

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

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Help with imwarp and affine2d

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

2 个评论
显示无隐藏无

更多回答（3 个）

3 个评论
显示 1更早的评论隐藏 1更早的评论

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

另请参阅

类别

标签

产品

Community Treasure Hunt

Help with imwarp and affine2d

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

采纳的回答

2 个评论 显示 无隐藏 无

更多回答（3 个）

3 个评论 显示 1更早的评论隐藏 1更早的评论

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

0 个评论 显示 -2更早的评论隐藏 -2更早的评论

另请参阅

类别

标签

产品

Community Treasure Hunt

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

2 个评论
显示无隐藏无

3 个评论
显示 1更早的评论隐藏 1更早的评论

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

0 个评论
显示 -2更早的评论隐藏 -2更早的评论