For the mathematical point of view.

Let A be an affine transformation and v a vector. The book "Geometric Tools for Computer Graphics" says: T(v) = T(Q - P) = T(Q) - T(P) But 1 + (-1) = 0. Don't the weights of the points need to sum to one? Q - P isn't even an affine combination... A vector being the difference of two points is not translated over affine transformation. So, vectors are transformed linearly, not affinely. For an affine transformation T(x) = Bx + c, where B is a square matrix whose columns are the target coordinates of the local unit axes and c the target position of the local origin, ...

Hello, All! Where I may get the affine transform algorhitm with a simple example in any language (Delphi/C/C++)? Vladimir. On Mon, 12 Jan 2004 12:16:35 +0300, "Getalo Vladimir" <korben@mariupol.net> wrote: > Hello, All! > > Where I may get the affine transform algorhitm with a simple example in any > language (Delphi/C/C++)? I'm not sure what you mean by "the affine transform algorithm". For instance any pair of "formulas" x' = a1*x + b1*y + c1 y' = a2*x + b2*y + c2 where a*,b*,c* are real numbers defines an affine mappin...

In books like "Geometric Tools for Computer Graphics" it seems that they assume a transformation is affine to construct the matrix representation without proving it is affine first. In particular, they often use the step: T(P) = T(Q + v) = T(Q) + T(v) = Q + T(v), where T(Q) = Q because Q is invariant under the transform. But how is T(Q + v) = T(Q) + T(v) legal until they have proved it is an affine transform? "vsgdp" <hello@null.com> wrote in message news:TfZtg.6686$5K2.5606@fed1read03... > In books like "Geometric Tools for Computer Graphics&quo...

hi, how would you use the built in java 'affine transformations' found here :- http://java.sun.com/j2se/1.4.2/docs/api/java/awt/geom/AffineTransform.html#rotate(double) for example, lets say i needed to shear the point (2,3), how would i use these commands to accomplish this? thanks jeremy watts Jeremy Watts wrote, under subject 'affine transformations': > hi, > > how would you use the built in java 'affine transformations' found > here :- > http://java.sun.com/j2se/1.4.2/docs/api/java/awt/geom/AffineTransform.html#rotate(double) > > for examp...

Hello! I've got an image and I've tried to use the cp2tform function to map an image in a grid. I've defined these grids: >> grid_X=[0.0:1/(nx-1):1.0]; >> grid_Y=[0.0:1/(ny-1):1.0]; I've defined this matrix: > A=[0 0; 1 0; 1 1; 0 1]; I've selected 4 vertex from the image in this way: imshow(im); angoli=ginput(4); angoli = 173 108 468 133 510 391 138 379 At this point I've used the function cp2tform: >> tform=cp2tform(A, angoli, 'projective'); >> H=(tform.tdata.Tinv)'; Now I would get the coordinates of the image ...

Hi everyone, I need to create an affine transformation matrix with the following order: - translation in the x direction - uniform scaling in x and y - and a rotation about the image center. Can someone tell me what the affine matrix would look like? Ia m having some confusion with the homogeneous coordinates... Cheers, Anja "Anja" <anja.ende@googlemail.com> wrote in message news:5316ad5f-98de-4b8c-a8bc-da2af936147e@e6g2000prf.googlegroups.com... > I need to create an affine transformation matrix with the following > order: > > - translation in the x direction...

Hi, I have an affine 2x2 matrix. How do I get the transformed ("global") scale factors sx, sy? I mean the scale factors which could be applied to the already transformed (global) points. This need is a bit untypical. But I need this for drawing a thick line. I already have the global line points, but I also need to draw the thickness which depends on the matrix too. ( the typical way is to draw a line as transformed polygon, but not in my case). I tried to get the scale factor by transforming a vector, but this is obviously wrong. For example. I transformed (sx = 1,sy = 1), and thus...

Hello, I am using the following code to align several frames: The original images are 4096*4096. Due to speed accuracy, I found it more suitable to re-size the images to 512*512 and executed the following code: while ii < length(images) % Read in new frame imgA = imgB; imgAp = imgBp; imgB = imresize(imread(cs{ii}),[512,512]); % Estimate transform from frame A to frame B, and fit as an s-R-t H = cvexEstStabilizationTform(imgA,imgB); HsRt = cvexTformToSRT(H); ...

I have a problem with transform coding .I have write matlab code for fourier transform and cosine transform Transform Coding on a jpeg image and compae the results (a) Write a program to compute the information loss associated with the following transform coding schemes: Case 1 Case 2 Transform: Fourier Cosine Subimage Size: 8 x 8 8 x 8 Bit Allocation: 8-largest coding 8-largest coding Use the routines developed in Project 08-01 to quantify the loss of information. Download the image in Fig. 8.23 and use the program to compare Cases 1 and 2. (b) Gradually decrease...

I am unsure how wavelet transform is performed in MATLAB. Do CWT and DWT functions compute the coefficients using Mallat's Pyramidal algorithm and filter banks? If not, what is the algorithm behind the functions? ...

I am trying to transform an image (2d or 3d) in 3 dimensions. I have made my 3d transform matrix using 'maketform' function. Then, I use 'tformfwd' function to actually apply this transformation on the image. This is where I am having problems. It gives me an error for missmatch dimensions. Are there any simpler functions to solve this problem?? Any Idea what am i doing wrong? Any suggestion will be very helpful. Thanks AG ****************************************************** function T = afft3(alpha, beta, gamma, sx,sy,sz,tx,ty,tz) R1 = [ sx*cos(gamma)*cos(beta), -sy*sin(ga...

Hello All, I am new to MATLAB and the process for creating custom documentation. I want to format my documentation the way MATLAB formats theirs as delivered as opposed to displaying my documentation in a supplementary CHM as the MATLAB documentation suggests. The reason for using DITA is that there will be two documentation types--PDF and MATLAB--and I want to leverage the single source aspect of DITA among some of its other features. If you have any hints or experience with handling challenges like this, it'd be great to hear from you. Alan ...

Hi there, I am facing a problem of calculating the differentiation of the affine transformation w.r.t. the image intensity and the transfromation parameters. May I ask if anyone has an idea how to do it in Matlab please? For example: I have an image I and 6 input parameters: affineKernelMatrix = [ 1 0 0; 0 1 0; 0 0 1]; affineKernelMatrix(1:3, 1:2) = reshape(inputsParameters(1:6), 3, 2); affineTransform = maketform('affine', affineKernelMatrix); affineTransformedImage = imtransform(I, affineTransform, ... 'UData', udata, 'VData', vdata, ... 'XData', ...

Hi, Does matlab have any facility for fitting an unknown affine transform? I need to read more on the subject, but I have 3 pairs of points. I want to find an affine transform which satisfies all of them (or the best affine transform possible for all 3 I guess). Thanks ...

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