Is there a way to make NSAffineTransform from CGAffineTransform?

Question

I'm trying to convert the iOS code to OSX code, and having some difficulties with graphics porting.

Under iOS I had this:

NSRect rect = NSMakeRect(centerX.doubleValue - width.doubleValue / 2, 
                         centerY.doubleValue - height.doubleValue / 2, 
                         width.doubleValue, height.doubleValue);

UIBezierPath * path = nil;

switch (self.shape) 
{
    case HSTargetShapeInvisible:
        path = [UIBezierPath bezierPath];
        break;
    case HSTargetShapeOval:
        path = [UIBezierPath bezierPathWithOvalInRect:rect];
        break;
    case HSTargetShapeRectangle:
        path = [UIBezierPath bezierPathWithRect:rect];
        break;
    default:
        break;
}

CGAffineTransform translate = CGAffineTransformMakeTranslation(-1 * centerX.doubleValue, 
                                                               -1 * centerY.doubleValue);
[path applyTransform:translate];

CGAffineTransform rotate = CGAffineTransformMakeRotation(rotation.doubleValue / 180 * M_PI);
[path applyTransform:rotate];

translate = CGAffineTransformMakeTranslation(centerX.doubleValue, centerY.doubleValue);
[path applyTransform:translate];

and this worked perfectly...then I rewrote it this way for OSX:

NSRect rect = NSMakeRect(centerX.doubleValue - width.doubleValue / 2,
                         centerY.doubleValue - height.doubleValue / 2, 
                         width.doubleValue, height.doubleValue);

NSBezierPath * path = nil;

switch (self.shape) 
{
    case HSTargetShapeInvisible:
        path = [NSBezierPath bezierPath];
        break;
    case HSTargetShapeOval:
        path = [NSBezierPath bezierPathWithOvalInRect:rect];
        break;
    case HSTargetShapeRectangle:
        path = [NSBezierPath bezierPathWithRect:rect];
        break;
    default:
        break;
}

NSAffineTransform *rot = [NSAffineTransform transform];
NSAffineTransform *pos = [NSAffineTransform transform];

[pos translateXBy:-1*centerX.doubleValue yBy:-1*centerY.doubleValue];

[rot rotateByRadians:rotation.doubleValue / 180 * M_PI];

[pos translateXBy:centerX.doubleValue
              yBy:centerY.doubleValue ];

[rot appendTransform:pos];
[path transformUsingAffineTransform:rot];

And this doesn't work the same way. Does anyone know where the problem is?!

Any kind of help is highly appreciated!

The pos transforms cancel each other out. Apply all operations to the same transform, that should work. — Gerd K, Sep 03 '13 at 18:33

score 1 · Accepted Answer · answered Sep 04 '13 at 04:10

Your original code uses three transforms, you've now tried to do it with two. Just go back to three (using distinct variables to make it clear):

NSAffineTransform *pos1 = [NSAffineTransform transform];   
[pos1 translateXBy:-1*centerX.doubleValue yBy:-1*centerY.doubleValue];
[path transformUsingAffineTransform:pos1];

NSAffineTransform *rot = [NSAffineTransform transform];
[rot rotateByRadians:rotation.doubleValue / 180 * M_PI];
[path transformUsingAffineTransform:rot];

NSAffineTransform *pos2 = [NSAffineTransform transform];
[pos2 translateXBy:centerX.doubleValue yBy:centerY.doubleValue];
[path transformUsingAffineTransform:pos2];

If you wish to just use one transformUsingAffineTransform: you can delete the three uses above and add the code:

[pos1 appendTransform:rot];
[pos1 appendTransform:pos2];
[path transformUsingAffineTransform:pos1];

You can even do it with one, but note the order - work from last to first:

NSAffineTransform *compound = [NSAffineTransform transform];
[compound translateXBy:centerX.doubleValue yBy:centerY.doubleValue];
[compound rotateByRadians:rotation.doubleValue / 180 * M_PI];
[compound translateXBy:-1*centerX.doubleValue yBy:-1*centerY.doubleValue];
[path transformUsingAffineTransform:compound];

HTH

Is there a way to make NSAffineTransform from CGAffineTransform?

1 Answers1