iOS 之渐变颜色

#import <UIKit/UIKit.h>

/**
 渐变方式

 - IHGradientChangeDirectionLevel:              水平渐变
 - IHGradientChangeDirectionVertical:           竖直渐变
 - IHGradientChangeDirectionUpwardDiagonalLine: 向下对角线渐变
 - IHGradientChangeDirectionDownDiagonalLine:   向上对角线渐变
 */
typedef NS_ENUM(NSInteger, IHGradientChangeDirection) {
    IHGradientChangeDirectionLevel,
    IHGradientChangeDirectionVertical,
    IHGradientChangeDirectionUpwardDiagonalLine,
    IHGradientChangeDirectionDownDiagonalLine,
};

@interface UIColor (IHGradientChange)

/**
 创建渐变颜色

 @param size       渐变的size
 @param direction  渐变方式
 @param startcolor 开始颜色
 @param endColor   结束颜色

 @return 创建的渐变颜色
 */
+ (instancetype)bm_colorGradientChangeWithSize:(CGSize)size
                                     direction:(IHGradientChangeDirection)direction
                                    startColor:(UIColor *)startcolor
                                      endColor:(UIColor *)endColor;


// 其他曲线渐变暂不考虑

@end

#import "UIColor+IHGradientChange.h"

@implementation UIColor (IHGradientChange)

+ (instancetype)bm_colorGradientChangeWithSize:(CGSize)size
                                     direction:(IHGradientChangeDirection)direction
                                    startColor:(UIColor *)startcolor
                                      endColor:(UIColor *)endColor {
    
    if (CGSizeEqualToSize(size, CGSizeZero) || !startcolor || !endColor) {
        return nil;
    }
    
    CAGradientLayer *gradientLayer = [CAGradientLayer layer];
    gradientLayer.frame = CGRectMake(0, 0, size.width, size.height);

    CGPoint startPoint = CGPointZero;
    if (direction == IHGradientChangeDirectionDownDiagonalLine) {
        startPoint = CGPointMake(0.0, 1.0);
    }
    gradientLayer.startPoint = startPoint;
    
    CGPoint endPoint = CGPointZero;
    switch (direction) {
        case IHGradientChangeDirectionLevel:
            endPoint = CGPointMake(1.0, 0.0);
            break;
        case IHGradientChangeDirectionVertical:
            endPoint = CGPointMake(0.0, 1.0);
            break;
        case IHGradientChangeDirectionUpwardDiagonalLine:
            endPoint = CGPointMake(1.0, 1.0);
            break;
        case IHGradientChangeDirectionDownDiagonalLine:
            endPoint = CGPointMake(1.0, 0.0);
            break;
        default:
            break;
    }
    gradientLayer.endPoint = endPoint;
    
    gradientLayer.colors = @[(__bridge id)startcolor.CGColor, (__bridge id)endColor.CGColor];
    UIGraphicsBeginImageContext(size);
    [gradientLayer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage*image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return [UIColor colorWithPatternImage:image];
}
@end