How to create a black UIImage?

Question

I've looked around everywhere, but I can't find a way to do this. I need to create a black UIImage of a certain width and height (The width and height change, so I can't just create a black box and then load it into a UIImage). Is there some way to make a CGRect and then convert it to a UIImage? Or is there some other way to make a simple black box?

If you just need a black box, create a `UIView` using your `CGRect` for the `frame`, set the `backgroundColor` to `[UIColor blackColor]`, and then add this new `UIView` to your existing view (e.g. `self.view` if doing this from a controller), using `addSubview`. — Rob, Apr 14 '13 at 19:38
Closely related: [For swaths of color, which is cheaper, UIView or UIImage?](http://stackoverflow.com/q/13885588) See also: [Overlaying a UIImage with a color](http://stackoverflow.com/q/845278), which has [an answer](http://stackoverflow.com/a/10620128/603977) that tells you how to do what you're asking for. — jscs, Apr 14 '13 at 19:42

score 25 · Accepted Answer · edited Sep 17 '21 at 05:26

Depending on your situation, you could probably just use a UIView with its backgroundColor set to [UIColor blackColor]. Also, if the image is solidly-colored, you don't need an image that's actually the dimensions you want to display it at; you can just scale a 1x1 pixel image to fill the necessary space (e.g., by setting the contentMode of a UIImageView to UIViewContentModeScaleToFill).

Having said that, it may be instructive to see how to actually generate such an image:

Objective-C

CGSize imageSize = CGSizeMake(64, 64);
UIColor *fillColor = [UIColor blackColor];
UIGraphicsBeginImageContextWithOptions(imageSize, YES, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
[fillColor setFill];
CGContextFillRect(context, CGRectMake(0, 0, imageSize.width, imageSize.height));
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Swift

let imageSize = CGSize(width: 420, height: 120)
let color: UIColor = .black
UIGraphicsBeginImageContextWithOptions(imageSize, true, 0)
let context = UIGraphicsGetCurrentContext()!
color.setFill()
context.fill(CGRect(x: 0, y: 0, width: imageSize.width, height: imageSize.height))
let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()

score 6 · Answer 2 · answered Apr 14 '13 at 19:47

6

UIGraphicsBeginImageContextWithOptions(CGSizeMake(w,h), NO, 0);
UIBezierPath* p =
    [UIBezierPath bezierPathWithRect:CGRectMake(0,0,w,h)];
[[UIColor blackColor] setFill];
[p fill];
UIImage* im = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

Now im is the image.

That code comes almost unchanged from this section of my book: http://www.apeth.com/iOSBook/ch15.html#_graphics_contexts

answered Apr 14 '13 at 19:47

matt

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Solid. The only thing I would change is that `opaque` can be set to `YES` since we're presumably drawing an opaque color into the context. – warrenm Apr 14 '13 at 19:53
Actually if you set `opaque` to YES I think you don't even have to draw the black filled rectangle! :) An opaque graphics context *is* black. – matt Apr 14 '13 at 19:58
Good catch. I wonder if that's documented anywhere or if it's just an implementation quirk. – warrenm Apr 14 '13 at 22:07
It's documented in my book so I hope it's *not* an implementation quirk! – matt Apr 14 '13 at 22:08

score 3 · Answer 3 · answered Mar 13 '17 at 23:00

Swift 3:

func uiImage(from color:UIColor?, size:CGSize) -> UIImage? {

    UIGraphicsBeginImageContextWithOptions(size, true, 0)
    defer {
        UIGraphicsEndImageContext()
    }

    let context = UIGraphicsGetCurrentContext()
    color?.setFill()
    context?.fill(CGRect.init(x: 0, y: 0, width: size.width, height: size.height))
    return UIGraphicsGetImageFromCurrentImageContext()
}

score 2 · Answer 4 · answered Mar 21 '20 at 12:55

Like this

let image = UIGraphicsImageRenderer(size: bounds.size).image { _ in
      UIColor.black.setFill()
      UIRectFill(bounds)
}

As quoted in this WWDC vid

There's another function that's older; UIGraphicsBeginImageContext. But please, don't use that.

score 0 · Answer 5 · answered May 24 '17 at 05:17

Here is an example that creates a black UIImage that is 1920x1080 by creating it from a CGImage created from a CIImage:

let frame = CGRect(origin: CGPoint(x: 0, y: 0), size: CGSize(width: 1920, height: 1080))
let cgImage = CIContext().createCGImage(CIImage(color: .black()), from: frame)!
let uiImage = UIImage(cgImage: cgImage)

How to create a black UIImage?

5 Answers5

Objective-C

Swift

Linked