## post processing: the Gimp perspective tool is not really transforming

I have uploaded a screenshot below to illustrate the problem. I dragged a jpeg to Gimp, clicked on the perspective tool and then tried to use it … but as you can see, it's not really transforming the image. Why is this so?

Click to enlarge the image.

## Transforming ParametricFunction into expression depending on the parameter

As a result of resolving an ODE system using `ParametricNDSolveValue` I get 4 functions, each one of them. Parametric Function depending on the parameter specified in `ParametricNDSolveValue`.

Even though what I want seems "simple" to me, I have searched the documentation and this site without success, so here is my question:

Can I transform my solution? Parametric Function in an expression of some kind? The motivation is to manipulate this expression, and this may involve different software.

If that is not possible, is there any other way in Mathematics to solve a $$2 times 2$$ System of EDOs at a point with a free parameter? Here is the question where I first asked about that.

## opengl – Transforming a length into a trunk projection

How do I calculate the screen lengths of the position vectors aligned with the axis after a frustum projection transformation?

Background:

In Java I create a frustum projection matrix via

``````Matrix.frustumM (projMatrix, 0, left, right, top bottom, near, far);
``````

and a view matrix via

``````Matrix.setLookAtM (viewMatrix, 0,
0, 0, -2.5, // eye position
0, 0, 0 // search position
0, -1, 0); // address above
``````

I also know how many GL units of width and height is the screen of my device, let's say `width` Y `height`. If my game tokens are `dx` Y `dy` GL units in size, then for a spelling projection I can calculate `width / dx` Y `height / dy` to determine how many squares you should have horizontally and vertically (approximately).

But with a trunk projection, which basically is always looking down according to the previous definition, this does not give me the correct result.

(Keep in mind that my tiles are always placed in the `x / y` airplane in `z = -1`

Of course I understand why, this is because the further away from the camera the smaller lengths are made. But how do I transform my `dx` Y `dy` values ​​to deal with this?

I have tried:

• divide my `dx` Y `dy` by `1 + 2.5 + 1 = 4.5` since that is the distance from the eye to the plane of the tile.

• Multiplying the projection and view matrices (and both together) by the vector (dx, 0, 0, 1) for example.

But these do not work.

I also hear that the projection matrix has a `w` component in the lower right part of the matrix, which may have something to do with the z-scale, but I'm not sure if it's on the right track.

Any advice welcome. I will continue investigating.

## – primaverabss – Transforming a FP into FA (Sales Documents)

Goodnight everyone,

I am trying to make the transformation of Sales Documents, in the case of a Pro-form in an Invoice, but it gives an error because the origin does not have Warehouse in the Lines.
How can I do to add the store I want?

I have the following code that works if you have Warehouse:

``````

On Error GoTo Error
Dim objDocOrigen The GcpBEDocumentoVenda
ObjDocOrigen = motor.Comercial.Vendientes.Edita ("000", cbOrigTipoDoc.Text, cbOrigSerie.Text, CInt (cbOrigDoc.Text))

Dim objDocDestino The GcpBedocumentoVenda
objDocDestino = New GcpBEDocumentoVenda
objDocDestino.Entity = objDocOrigen.Entity
objDocDestino.Tipodoc = cbDestTipoDoc.Text
objDocDestino.Serie = cbDestSerie.Text
objDocDestino.CondPag = objDocOrigem.CondPag

Dim Doc (0) As Object
Doc (0) = objDocOrigen