How to create a colored 1x1 UIImage on the iPhone dynamically?

Ian Terrell picture Ian Terrell · Jun 13, 2009 · Viewed 37.9k times · Source

I would like to create a 1x1 UIImage dynamically based on a UIColor.

I suspect this can quickly be done with Quartz2d, and I'm poring over the documentation trying to get a grasp of the fundamentals. However, it looks like there are a lot of potential pitfalls: not identifying the numbers of bits and bytes per things correctly, not specifying the right flags, not releasing unused data, etc.

How can this be safely done with Quartz 2d (or another simpler way)?

Answer

Matt Stevens picture Matt Stevens · Jun 14, 2009

You can use CGContextSetFillColorWithColor and CGContextFillRect for this:

Swift

extension UIImage {
    class func image(with color: UIColor) -> UIImage {
        let rect = CGRectMake(0.0, 0.0, 1.0, 1.0)
        UIGraphicsBeginImageContext(rect.size)
        let context = UIGraphicsGetCurrentContext()

        CGContextSetFillColorWithColor(context, color.CGColor)
        CGContextFillRect(context, rect)

        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return image
    }
}

Swift3

extension UIImage {
    class func image(with color: UIColor) -> UIImage {
        let rect = CGRect(origin: CGPoint(x: 0, y:0), size: CGSize(width: 1, height: 1))
        UIGraphicsBeginImageContext(rect.size)
        let context = UIGraphicsGetCurrentContext()!

        context.setFillColor(color.cgColor)
        context.fill(rect)

        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return image!
    }
}

Objective-C

+ (UIImage *)imageWithColor:(UIColor *)color {
    CGRect rect = CGRectMake(0.0f, 0.0f, 1.0f, 1.0f);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;
}