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

Question

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

Answer 1

I used Matt Steven's answer many times so made a category for it:

@interface UIImage (mxcl)
+ (UIImage *)squareImageWithColor:(UIColor *)color dimension:(int)dimension;
@end

@implementation UIImage (mxcl)
+ (UIImage *)squareImageWithColor:(UIColor *)color dimension:(int)dimension {
    CGRect rect = CGRectMake(0, 0, dimension, dimension);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

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

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

    return image;
}
@end

Answer 2

Here's another option based on Matt Stephen's code. It creates a resizable solid color image such that you could reuse it or change it's size (e.g. use it for a background).

+ (UIImage *)prefix_resizeableImageWithColor:(UIColor *)color {
    CGRect rect = CGRectMake(0.0f, 0.0f, 3.0f, 3.0f);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();

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

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

    image = [image resizableImageWithCapInsets:UIEdgeInsetsMake(1, 1, 1, 1)];

    return image;
}

Put it in a UIImage category and change the prefix.

Answer 3

Using Apple's latest UIGraphicsImageRenderer the code is pretty small:

import UIKit

extension UIImage {
    static func from(color: UIColor) -> UIImage {
        let size = CGSize(width: 1, height: 1)
        return UIGraphicsImageRenderer(size: size).image(actions: { (context) in
            context.cgContext.setFillColor(color.cgColor)
            context.fill(.init(origin: .zero, size: size))
        })
    }
}

Answer 4

To me, a convenience init feels neater in Swift.

extension UIImage {

    convenience init?(color: UIColor, size: CGSize = CGSize(width: 1, height: 1)) {

        let rect = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        UIGraphicsBeginImageContext(rect.size)
        guard let context = UIGraphicsGetCurrentContext() else {
            return nil
        }

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

        guard let image = context.makeImage() else {
            return nil
        }
        UIGraphicsEndImageContext()

        self.init(cgImage: image)
    }

}

Answer 5

Ok, this won't be exactly what you want, but this code will draw a line. You can adapt it to make a point. Or at least get a little info from it.

Making the image 1x1 seems a little weird. Strokes ride the line, so a stroke of width 1.0 at 0.5 should work. Just play around.

- (void)drawLine{

UIGraphicsBeginImageContext(CGSizeMake(320,300));

CGContextRef ctx = UIGraphicsGetCurrentContext();

float x = 0;
float xEnd = 320;
float y = 300;

CGContextClearRect(ctx, CGRectMake(5, 45, 320, 300));

CGContextSetGrayStrokeColor(ctx, 1.0, 1.0);

CGContextSetLineWidth(ctx, 1);
CGPoint line[2] = { CGPointMake(x,y), CGPointMake(xEnd, y) };

CGContextStrokeLineSegments(ctx, line, 2);

UIImage *theImage=UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}

Answer 6

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;
}