# Thread: How Can make a circle rotate by the center of it ?

1. ## How Can make a circle rotate by the center of it ?

How Can make a circle rotate by the center of it ?ths

2. ## Re: How Can make a circle rotate by the center of it ?

Originally Posted by vinceno1
How Can make a circle rotate by the center of it ?ths
Uh, how can you tell if a circle is rotating in the first place?

3. ## Re: How Can make a circle rotate by the center of it ?

Now, I draw a picture of a circle, when I use the fun of rotate, the picture rotate by the picture's left top position,but I want the picture to rotate by its' center.

4. ## Re: How Can make a circle rotate by the center of it ?

Originally Posted by vinceno1
Now, I draw a picture of a circle, when I use the fun of rotate, the picture rotate by the picture's left top position,but I want the picture to rotate by its' center.
If your picture contains only circle than i dont think there is any diff in the output image whether it is rotated from the top left or from center. And one more thing that its of no use of rotating the circle. I think you are need to explain a something more regarding your query.

5. ## Re: How Can make a circle rotate by the center of it ?

He's talking about using the rotate function. By default it rotates around the top left of the image (and rotates the image out of the frame at more than 90 degrees). But you can specify an origin to rotate it around the center or some other axis.

I've never played with the functions to know the tricks.

Here are some refs:
http://doc.qt.nokia.com/4.6-snapshot/coordsys.html
http://doc.qt.nokia.com/4.6-snapshot/demos-affine.html
http://doc.qt.nokia.com/4.6-snapshot...ormations.html

6. ## Re: How Can make a circle rotate by the center of it ?

All so you could calculate the new location and offset the image inside a container to move as it works,

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