iOS中的四点渐变 [英] Four point gradient in iOS

问题描述

我计划创建一个四点渐变，如下图所示，通过核心图形绘制两个线性渐变，并使用第三个黑白线性渐变在它们之间进行遮罩。

I am planing to create a four point gradient, pictured below, by drawing two linear gradients via core graphics and masking between them with a third black and white linear gradient.

是否有更有效的方法使用核心图形或其他绘制四点渐变？

Is there a more efficient way to draw a four point gradient using core graphics, or other?

推荐答案

您可以在使用时保存遮罩渐变一个CGBlendMode。控制确切的颜色更难。但是如果这对你来说并不重要，那么在代码行方面可能会更有效率，也可能在性能方面更有效。

You can save the mask gradient when you use a CGBlendMode. It's just harder to control the exact colors. But if that's not important for you, it could be a little more efficient in terms of lines of code and maybe also in terms of performance.

这是一个随机的例子colors和CGBlendModeExclusion（CGBlendModeDifference给你类似的效果）

Here's an example with some random colors and CGBlendModeExclusion (CGBlendModeDifference gives you a similar effect)

- (void) drawRect:(CGRect)rect
{
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextSetBlendMode(ctx, kCGBlendModeExclusion);
    CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();

    CGFloat col1[8] = {
        1.0, 0.0, 0.0, 1.0,
        0.0, 0.0, 1.0, 1.0
    };
    CGGradientRef grad1 = CGGradientCreateWithColorComponents (space, col1, NULL, 2);
    CGContextDrawLinearGradient(ctx, grad1, CGPointMake(0, 0), CGPointMake(0, 320), 0);


    CGFloat col2[8] = {
        1.0, 0.5, 0.0, 1.0,
        0.0, 1.0, 0.0, 1.0
    };
    CGGradientRef grad2 = CGGradientCreateWithColorComponents (space, col2, NULL, 2);
    CGContextDrawLinearGradient(ctx, grad2, CGPointMake(0, 0), CGPointMake(320, 0), 0);

    CGGradientRelease(grad1);
    CGGradientRelease(grad2);
    CGColorSpaceRelease(space);
}

这篇关于iOS中的四点渐变的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！