Question

I’m implementing a basic speedometer using an image and rotating it. However, when I set the initial rotation (at something like 240 degrees, converted to radians) It rotates the image and makes it much smaller than it otherwise would be. Some values make the image disappear entirely. (like M_PI_4)

the slider goes from 0-360 for testing.

the following code is called on viewDidLoad, and when the slider value is changed.

-(void) updatePointer
{
    double progress = testSlider.value;
    progress += pointerStart
    CGAffineTransform rotate = CGAffineTransformMakeRotation((progress*M_PI)/180);
    [pointerImageView setTransform:rotate];
}

EDIT: Probably important to note that once it gets set the first time, the scale remains the same. So, if I were to set pointerStart to 240, it would shrink, but moving the slider wouldn’t change the scale (and it would rotate it as you’d suspect) Replacing “progress” with 240 in the transformation does the same thing. (shrinks it.)

Answer 1

I was able to resolve the issue for anybody who stumbles across this question. Apparently the image is not fully loaded/measured when viewDidLoad is called, so the matrix transforms that cgAffineTransform does actually altered the size of the image. Moving the update code to viewDidAppear fixed the problem.