asked on

Scaling rectangle

Hi,

I drew a rectangle in a TImage object.

The size of TImage is for example width = W and Height = H.

The rectangle has 4 coordinate positions, X1, Y1, X2, Y2.

Then, I proportionally shrink the TImage to be this size: width = W1 and Height = H1.

So, anyone know a formula to calculate the new X1, Y1, X2, and Y2, so the rectangle will still be proportional ?

Thanks

kretzschmar

just from head, not tested, and maybe possible wrong

scalingfactor := NewHeight/OldHeight;

newX1 := x1*scalingfactor;
newY1 := y1*scalingfactor;
newX2 := y2*scalingfactor;
newY2 := y2*scalingfactor;

meikl ;-)

Ferruccio Accalai

x := X*W1 div W;
x1 := X1*W1 div W;
y := y*H1 div H;
y1 := y1*H1 div H;

F68 ;-)

Ferruccio Accalai

this time you're the faster meikl :))

kretzschmar

i'm not sure, if my calculation is correct, f68 :-)

Ferruccio Accalai

infact looking better in your calculation y must depend on Width scaling factor, that could be different from the height one...
SO

WSCalingFactor := NewWIdth/OldWIdth;
HSCalingFactor := NewHeight/OldHeight;

x1 := x1*WSCalingFactor;
x2 := x2*WScalingFactor;
y1 := y1*HSCalingFactor;
y2 := y2*HScalingFactor;

F68 ;-)

Ferruccio Accalai

ops...NewWIdth div OldWIdth...etc. etc. (result must be integer, not real)

kretzschmar

>ops...NewWIdth div OldWIdth...etc. etc. (result must be integer, not real)

just use round or trunc

>WSCalingFactor := NewWIdth/OldWIdth;
>HSCalingFactor := NewHeight/OldHeight;

i decided to use one scalingfactor, because
if the image is scaled proportional, then
WSCalingFactor and HSCalingFactor
should have the same value

meikl ;-)

muis2002

ASKER

Well, after I tried, it does not works :( not because the calculation, but because of the way TImage stretching :(

I cant get the W1 and H1 (width and height after stretched proportionally).

Original TImage size W * H

then I have newTImage with "smaller" size (let say Wx and Hx).
I assigned TImage to the newTImage, so that newTImage contains TImage bitmap.

But then, I cant get the stretched image size in newTImage.

I checked newTImage.Width , it will always Wx
I checked newTImage.Picture.Width, it will always W (the same with TImage.Width).

kretzschmar

the picture width never changes,
only the visualizing of the TImage
is adjusted (autostretch-property is set to true)

if you want the picture scaled physically,
then use canvas-methods like

- Stretchdraw
- copyrect

or api like
- BitBlt

to create a new scaled picture

meikl ;-)

ASKER CERTIFIED SOLUTION

kretzschmar

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