SDL_rotozoom offset

Engines and Middleware Programming

Started by Zeophlite June 23, 2005 05:57 AM

5 comments, last by gumpy 18 years, 10 months ago

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June 23, 2005 05:57 AM

When you rotate an image or scale an image with SDL_rotozoom, the center of the new image is slightly off (to the right and below slightly) To illustrate: http://vicious.sixlabs.org/normal.bmp (regular) http://vicious.sixlabs.org/45.bmp (rotated 45 degrees) The red dot is the center of the image Is there a function that finds the offset of the img (both rotating and zooming the picture), ie, moves the rotated image to the left and upwards so the red dot is at the same location as the red dot is at http://vicious.sixlabs.org/normal.bmp Thanks in advance

Rob Loach

1,504

June 23, 2005 10:27 PM

No, the rotation is correct. The problem is that when you rotate it, the size gets bigger according to the rotation. If you rotate a perfect square, it'll turn into a diamond with a larger respective width and height. To fix the problem, instead of drawing at (x, y) draw at (x-width/2, y-height/2). You'll find that it will then draw at the center point of x and y. This is the solution I took when working on Blastoids.