Core Graphices 设置渐变
Quartz 提供了两种设置渐变的方式 CGShadingRef and CGGradientRef
尝试CGGradientRef 的使用
import <UIKit/UIKit.h> @interface GradientDemoA : UIView @property (nonatomic,copy,nonnull)NSArray *colorArray;
@property (nonatomic,copy,nonnull) NSArray *locations;
@property (nonatomic,assign)CGPoint startPoint;
@property (nonatomic,assign)CGPoint endPoint; - (void)showViewWithColorArray:(NSArray * _Nullable)colorArray GradientLocations:(NSArray * _Nullable)loc startPoint:(CGPoint)startPoint endPoint:(CGPoint)endPoint;
@end
#import "GradientDemoA.h"
@implementation GradientDemoA
- (instancetype)initWithFrame:(CGRect)frame{
if (self = [super initWithFrame:frame]) {
self.backgroundColor = [UIColor whiteColor];
}
return self;
}
- (void)showViewWithColorArray:(NSArray *)colorArray GradientLocations:( NSArray *)loc startPoint:(CGPoint)startPoint endPoint:(CGPoint)endPoint{
self.colorArray = colorArray;
self.locations = loc;
self.startPoint = startPoint;
self.endPoint = endPoint;
[self setNeedsDisplay];
}
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient;
size_t num_location = self.colorArray.count;
CGFloat components[self.colorArray.count*];
for (int i=; i<self.colorArray.count; i++) {
CGFloat *colorComponents = (CGFloat *)CGColorGetComponents(((UIColor *)self.colorArray[i]).CGColor);
components[+i*] = colorComponents[];
components[+i*] = colorComponents[];
components[+i*] = colorComponents[];
components[+i*] = colorComponents[];
}
CGFloat gendientLocations[self.locations.count];
for (int j= ; j<self.locations.count; j++) {
gendientLocations[j] = (CGFloat)([self.locations[j] doubleValue]);
}
// 参数的意义
/*
颜色空间
components cgfloat 数组 RGB的颜色值
{
red1，green1，blue1，alpha1，
red2，green2，blue2，alpha2，
...
}
gendientLocations 颜色渐变的点
CGFloat gendientLocation[2] = {0.0,.......,1.0};
num_location 颜色渐变点的个数；
*/
gradient = CGGradientCreateWithColorComponents(colorSpace, components, gendientLocations, num_location);
/*
开始点与结束点的tan值决定了渐变的角度；
**/
// CGContextDrawLinearGradient(context, gradient, self.startPoint, self.endPoint, kCGGradientDrawsBeforeStartLocation);
CGContextDrawRadialGradient(context, gradient, CGPointMake(, ), , CGPointMake(, ), , kCGGradientDrawsAfterEndLocation);
CGGradientRelease(gradient);
}
@end
参数更具体的意义请查看：
http://blog.csdn.net/u012890117/article/details/17606755
测试代码：
- (void)gradientColor{
GradientDemoA *my = [[GradientDemoA alloc] initWithFrame:CGRectMake(, , , )]; [my showViewWithColorArray:@[[[UIColor redColor] colorWithAlphaComponent:1.0],[[UIColor redColor] colorWithAlphaComponent:0.0],[[UIColor redColor] colorWithAlphaComponent:0.8]] GradientLocations: @[@(0.1),@0.5,@(0.8)] startPoint:CGPointMake(,) endPoint:CGPointMake(, )]; [self.view addSubview:my];
}
图1：
图2：