Pic.Rotate cut off pics

[riveryu]

How do I avoid cutting off parts of a picture when rotating a picture at a certain point?

[Sean]

Can you give us the code that had this error in it, so we can see what is wrong. Hard to tell when we don't see exactly what you see.

[isaiahk9]

an inefficient way (but easy) would to just add more white around the edges of the picture, so that only white is cut off and we don't see it

[riveryu]

Here is an example of the situation, maybe im using Pic.Rotate wrongly...

Turing:

View.Set ("graphics:1000;600,offscreenonly") var picID:int var picID1 :int drawfillbox (100,100,200,200,red) picID:=Pic.New(100,100,200,200) for i:1..360 picID1:=Pic.Rotate(picID,i,100,100) Pic.Draw(picID1,100,100,0) delay(50) View.Update cls end for

[riveryu]

Thanks isaiahk9, that solved the problem.

Aside from that,is there an actual "efficient" way? Anyone?

[Tony]

Writing your own function would be the way to go for this one. Rotate just the non-white pixels for optimization. You could make it super fast if you pre-calculate some transformation matrices. Keeping equations more abstract requires more calculations run-time, but allows for greater flexibility.

This is how most of 2D graphics are handled -- rotation, scaling, shearing, reflections, projection

[Saad]

riveryu @ Wed May 14, 2008 7:21 pm wrote:

Thanks isaiahk9, that solved the problem.

Aside from that,is there an actual "efficient" way? Anyone?

A much better way would be to use 2D rotation.

The 2D rotation formula is the following


(TeX tags for the win)

This however works only for the origin, and as a result you want to tranlate it to the origin.

Some code that you might want to look at

Turing:

const AMOUNT_TO_ROTATE := 1 const NUMBER_OF_ROTATIONS := 360 const CENTER_X := 250 const CENTER_Y := 250 var x : real := 100 var y : real := 0 x += CENTER_X y += CENTER_Y for rotationIndex : 1 .. NUMBER_OF_ROTATIONS     x -= CENTER_X %% Move the point to the center     y -= CENTER_Y     %% Plug into the rotation formula     %% We will save them into new variables as we need to use to original x and y     var newX := x * cosd (AMOUNT_TO_ROTATE) - y * sind (AMOUNT_TO_ROTATE)     var newY := y * cosd (AMOUNT_TO_ROTATE) + x * sind (AMOUNT_TO_ROTATE)         x := newX     y := newY     x += CENTER_X  %% Move the point back away from the center     y += CENTER_Y     Draw.FillOval (round (x), round (y), 10, 10, black)     Time.Delay (10) end for

Now apply the rotation too all the points on the square

[riveryu]

Thanks a lot! Tony, Saad. When did you guys learn about transformation matrices? I wish I'll learn it in grade 10...Do you learn this in math courses? I dont like using something I dont understand...

I wish there is a list of topics for people to learn about from beginner to advanced just from programming theories(concepts thats feasible no matter the language).

Does such a list already exist? I would gladly make one for ppl if I know enough.

[syntax_error]

you dont need a math course per se, to learn them, if you have an interest: library. enough said.

[CodeMonkey2000]

Better yet, internet. Don't limit your education to just what you do in school.