Function should return float, but it gets messed up!

Question

Hi guys,

I'm going crazy here.

I have a function that should return a float number:

- (float) getHue:(UIColor *)original
{
    NSLog(@"getHue");
    const CGFloat *componentColors = CGColorGetComponents(original.CGColor);

    float red = componentColors[0];
    float green = componentColors[1];
    float blue = componentColors[2];

    float h = 0.0f;
    float maxChannel = fmax(red, fmax(green, blue));
    float minChannel = fmin(red, fmin(green, blue));
    if (maxChannel == minChannel)
        h = 0.0f;
    else if (maxChannel == red)
        h = 0.166667f * (green - blue) / (maxChannel - minChannel) + 0.000000f;
    else if (maxChannel == green)
        h = 0.166667f * (blue - red) / (maxChannel - minChannel) + 0.333333f;
    else if (maxChannel == blue)
        h = 0.166667f * (red - green) / (maxChannel - minChannel) + 0.666667f;
    else
        h = 0.0f;

    if (h < 0.0f)
        h += 1.0f;

    NSLog(@"getHue results: %f", h);

    return h;
}

The NSLog will trace it correctly (i.e: 0.005), but the actual return value of the function is NULL.

I've tried getting that value in so many ways and it never works.

float originalHue = [self getHue:original];

results in a building error, as it says: "incompatible types in initialization"

float *originalHue = [self getHue:original];

results in a null return.

I've tried other ways, but it never actually gets the value properly.

Any thoughts?

Cheers guys, Andre

Answer 1

I used your code but didn't find any issues. It is working fine for me. Just clean build your app once. Above code will work fine until h = 0.0005 if its beyond the value 0.0005 thats is 0.00005 or more, then you will get infinite value. So please check for it and do the necessary changes like using double/long instead.

Answer 2

Have you declared your method in the interface of your class? If so, did you per accident indicate a different return value (e.g. id)?

If it is not declared in your interface the compiler will treat the return value as id, so you would either need to declare it in the interface or cast the return value to a float.

Answer 3

Your code works fine for me using this to call it:

UIColor *aColor = [UIColor colorWithRed:0.3 green:0.1 blue:0.5 alpha:1.0];
float theHue = [self getHue:aColor];
NSLog(@"Float: %f", theHue);

Returns:

2010-04-07 11:49:33.242 Floating[8888:207] getHue
2010-04-07 11:49:33.243 Floating[8888:207] getHue results: 0.750000
2010-04-07 11:49:33.243 Floating[8888:207] Float: 0.750000