Re: NSAffineTransform question
Re: NSAffineTransform question
- Subject: Re: NSAffineTransform question
- From: Gregory Weston <email@hidden>
- Date: Wed, 25 Apr 2007 11:28:05 -0400
Janek Priimann wrote:
Right now the image is rotated around (0,0). To fix this problem:
float deltaX = imageRect.size.width * 0.5;
float deltaY = imageRect.size.height * 0.5;
[xform translateXBy:deltaX yBy:deltaY];
[xform rotateByDegrees:90];
[xform translateXBy:-deltaX yBy:-deltaY];
There's actually a bit more to do here. The above code will work if
the image is square and the lower-left corner of the result is
intended to be at the origin. Since we're dealing with a multiple of
90 degrees, you can just swap the x and y offsets for the final
translate (which is, for the OP, the first one in the code line). But
the offsets should also be adjusted by the lower-left corner of the
intended destination rectangle. And the destination rectangle itself
should not be modified ahead of time to reflect the rotated dimensions.
Ewan Delanoy wrote:
[xform concat];
[theImage drawInRect:drawingRect fromRect:imageRect
operation:NSCompositeSourceOver fraction:1.0];
[xform invert];
[xform concat];
Those last two lines aren't a reliable way to remove the transform.
I've seen what I consider trivial transforms fail to invert. If you
want to impose a transform just for a little while:
[NSGraphicsContext saveGraphicsState];
[theTransform concat];
// draw, draw, draw
[NSGraphicsContext restoreGraphicsState];
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