How to change size of thumb image of UISlider programmatically

Question

I would like to make the custom UISlider, something like this

|o----------| -> |-----O------| -> |------------〇|

the thumbImage will be small at the minimum value, it will increase the size during the slider value increase, otherwise it will decrease.

is anyone know how to do it?

Mercaptide

Answer 1

You can use this code:

+ (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
    //UIGraphicsBeginImageContext(newSize);
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0);
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
    UIGraphicsEndImageContext();
    return newImage;
}

Taken from here.

The extra work you will have, will be a method A that will call the imageWithImage:scaledToSize: when the UISlider's value changes.

Strategy

thx for Reply , i have added with the follow, am i right? But i test with trouble image size occur... float ratio = penSize_sld.value/( penSize_sld.maximumValue/2); CGSize ss= CGSizeMake(penSize_sld.currentThumbImage.size.widthratio, penSize_sld.currentThumbImage.size.heightratio); UIImage *changeImage = [UIImage imageWithImage:penSize_sld.currentThumbImage scaledToSize:ss]; [penSize_sld setThumbImage:changeImage forState:UIControlStateNormal]; if (sender == penSize_sld) { brushWidth = penSize_sld.value; } – Mercaptide

That work! Thanks JackyBoy float ratio = penSize_sld.value/( penSize_sld.maximumValue/2); if ( ratio < 0.8) { ratio = 0.8; } UIImage *thumbImage = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"drawview_dragbar_bu_1.png" ofType:nil]]; CGSize ss= CGSizeMake(thumbImage.size.width*ratio,thumbImage.size.height*ratio); UIImage *changeImage = [UIImage imageWithImage:thumbImage scaledToSize:ss]; [penSize_sld setThumbImage:changeImage forState:UIControlStateNormal]; ..... } – Mercaptide

Answer 2

Swift 3:

extension UIImage {

    func scaleToSize(newSize: CGSize) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
        draw(in: CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height))
        let newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext();
        return newImage
    }
}

Tolle