ios 如何在 iPhone 上动态创建彩色 1x1 UIImage？

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

提问by Ian Terrell

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

我想基于 UIColor 动态创建一个 1x1 UIImage。

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.

我怀疑这可以通过 Quartz2d 快速完成，我正在仔细阅读文档以了解基本原理。然而，看起来有很多潜在的缺陷：没有正确识别每个事物的位数和字节数，没有指定正确的标志，没有释放未使用的数据等。

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

如何使用 Quartz 2d（或其他更简单的方法）安全地完成此操作？

回答by Matt Stevens

You can use CGContextSetFillColorWithColorand CGContextFillRectfor this:

为此，您可以使用CGContextSetFillColorWithColor和CGContextFillRect：

Swift

迅速

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

斯威夫特3

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

目标-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;
}

回答by Ben Lachman

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).

这是基于 Matt Stephen 代码的另一个选项。它创建一个可调整大小的纯色图像，以便您可以重复使用它或更改它的大小（例如将其用作背景）。

+ (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.

将其放入 UIImage 类别并更改前缀。

回答by mxcl

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

我多次使用马特史蒂文的答案，所以为它做了一个分类：

@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

回答by bitwit

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

使用 Apple 最新的 UIGraphicsImageRenderer，代码非常小：

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))
        })
    }
}

回答by Mark Bridges

To me, a convenience init feels neater in Swift.

对我来说，Swift 中的便利 init 感觉更简洁。

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)
    }

}

回答by Corey Floyd

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.

好吧，这不是你想要的，但这段代码会画一条线。你可以调整它来表达观点。或者至少从中获取一些信息。

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.

使图像 1x1 看起来有点奇怪。笔画沿着这条线，所以宽度为 1.0 的笔画应该是 0.5。随便玩玩。

- (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();
}