How to create a colored 1x1 UIImage on the iPhone dynamically?
Solution 1
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;
}
Solution 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.
Solution 3
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
Solution 4
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))
})
}
}
Ian Terrell
Updated on May 22, 2020Comments
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Ian Terrell almost 4 years
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)?
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Admin about 12 yearsNice one :-) I would recommend putting this method into a category as a class method, then it can be added into a project simply, and invoked using a line like
[UIImage imageWithColor: [UIColor redColor]]
. -
hpique about 10 yearsIn case you're creating these images in a loop or using a bigger size, an optimisation would be to use an opaque canvas only if the color has alpha. Like this:
const CGFloat alpha = CGColorGetAlpha(color.CGColor); const BOOL opaque = alpha == 1; UIGraphicsBeginImageContextWithOptions(size, opaque, 0);
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fnc12 almost 9 yearsplease provide swift version
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Antzi almost 9 yearsIs there a way to make the swift one be a custom initializer instead ?
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Iulian Onofrei over 8 yearsWhy is
UIGraphicsGetCurrentContext()
returninnil
? Edit: I got it, I was passing0
for therect
'swidth
. -
Ian Newson over 7 yearsAdded Swift 3 port
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turingtested over 5 years@user577537 ...or in a catagory as an instance method of UIColor, so it would be even simpler
[[UIColor redColor] image]