CODEWITHSUNDEEP
iphoneuiimagerotationquartz-2doffset
woody993
woody993

Reputation: 659

UIImage Rotation Offset

I have the following code

- (void)ComputeRotationWithRadians:(CGFloat)rad {
    CGFloat width = exportImage.size.width;
    CGFloat height = exportImage.size.height;
    UIGraphicsBeginImageContext(CGSizeMake(width, height));
    CGContextRef ctxt = UIGraphicsGetCurrentContext();
    CGContextScaleCTM(ctxt, 1.0, -1.0);
    CGContextTranslateCTM(ctxt, 0.0, -exportImage.size.height);
    CGContextRotateCTM(ctxt, rad);
    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), exportImage.CGImage);
    exportImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    [imageView setImage:exportImage];
}

The issue is that the rotation happens around the bottom left corner, when it has been calculated around the center. Is there anyway to change this?

Upvotes: 0

Views: 771

Answers (1)

fbrereto
fbrereto

Reputation: 35925

Your code is translating the matrix before rotating it. Try flipping the calls to CGContextConcatCTM and CGContextTranslateCTM so you rotate first. Or perhaps you are looking for something else?

Upvotes: 1

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