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参考：http://www.jianshu.com/p/3e0e25fd9b85
CAGradientLayer类
CAGradientLayer类在苹果API文档中其说明为:CAGradientLayer类对其绘制渐变背景颜色、填充层的形状(包括圆角).
其继承关系图如下:
CAGradientLayer继承CAlayer,设置其属性都会有GPU绘制运算
用到的属性有:
- colors 渐变的颜色
- locations 颜色变化位置的取值范围
- startPoint 颜色渐变的起始位置:取值范围在(0,0)~(1,1)之间
- endPoint 颜色渐变的终点位置,取值范围也是在(0,0)~(1,1)之间 补充下:startPoint & endPoint设置为(0,0)(1.0,0)代表水平方向渐变,(0,0)(0,1.0)代表竖直方向渐变
-(void)graint{
CAGradientLayer *layer=[CAGradientLayerlayer];
layer.frame=self.creditCardNolabl.frame;
[layer setColors:@[(id)[UIColorredColor].CGColor, (id)[UIColorblueColor].CGColor]];
[self.creditCardNolabl.layeraddSublayer:layer];
//颜色上下渐变
[layer setStartPoint:CGPointMake(0, 0)];
[layer setEndPoint:CGPointMake(0, 1)];
}
//为透明度设置渐变效果
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];
UIColor *colorOne = [UIColor colorWithRed:(216/255.0) green:(0/255.0) blue:(18/255.0) alpha:1.0];
UIColor *colorTwo = [UIColor colorWithRed:(216/255.0) green:(0/255.0) blue:(18/255.0) alpha:0.0];
NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, colorTwo.CGColor, nil];
CAGradientLayer *gradient = [CAGradientLayer layer];
view.layer.masksToBounds = YES;
//设置开始和结束位置(设置渐变的方向)
gradient.startPoint = CGPointMake(0, 0);
gradient.endPoint = CGPointMake(1, 0);
gradient.colors = colors;
gradient.frame = CGRectMake(0, 0, 40, 40);
[view.layerinsertSublayer:gradientatIndex:0];
[self.view addSubview:view];
=====
-(UIImage *)drawcont{
UIGraphicsBeginImageContext(self.creditCardNolabl.frame.size);
CGContextRef context =UIGraphicsGetCurrentContext();
CGContextClip(context);
CGColorSpaceRef rgb =CGColorSpaceCreateDeviceRGB();
CGFloat colors[] =
{
204.0 / 255.0, 224.0 / 255.0, 244.0 / 255.0, 1.00,
29.0 / 255.0, 156.0 / 255.0, 215.0 / 255.0, 1.00,
0.0 / 255.0, 50.0 / 255.0, 126.0 / 255.0, 1.00,
};
CGGradientRef gradient =CGGradientCreateWithColorComponents
(rgb, colors, NULL,sizeof(colors)/(sizeof(colors[0])*4));
CGColorSpaceRelease(rgb);
CGContextDrawLinearGradient(context, gradient,CGPointMake
(0.0,0.0) ,CGPointMake(0.0,self.frame.size.height),
kCGGradientDrawsBeforeStartLocation);
UIImage *theImage =UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return theImage;
}
1-> 线性渐变
- (void)drawLinearGradient:(CGContextRef)context
path:(CGPathRef)path
startColor:(CGColorRef)startColor
endColor:(CGColorRef)endColor View:(UIView *)v
{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = { 0.0,1.0 };//这个是两种颜色的位置
// CGFloat locations[] = { 0.0, 0.5,1.0 };//这个是三种颜色的位置
// NSArray *colors = @[(__bridge id)startColor,(__bridge id)[UIColor blueColor].CGColor,(__bridge id)endColor];//渐变颜色的种类，要和上边的locations对应；
NSArray *colors = @[(__bridge id)startColor,(__bridge id)endColor];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);
// CGRect pathRect = CGPathGetBoundingBox(path);
//具体方向可根据需求修改
// CGPoint startPoint = CGPointMake(CGRectGetMinX(pathRect), CGRectGetMinY(pathRect));
// CGPoint endPoint = CGPointMake(CGRectGetMinX(pathRect), CGRectGetMaxY(pathRect));
CGPoint startPoint = CGPointMake(20,v.frame.size.height);
CGPoint endPoint = CGPointMake(20,0);
CGContextSaveGState(context);
CGContextAddPath(context, path);
CGContextClip(context);
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGContextRestoreGState(context);
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
-(UIImage *)getImageWithView:(UIView *)v{
//创建CGContextRef
UIGraphicsBeginImageContext(self.bounds.size);
CGContextRef gc = UIGraphicsGetCurrentContext();
//创建CGMutablePathRef
CGMutablePathRef path = CGPathCreateMutable();
//绘制Path
CGPathMoveToPoint(path, NULL, 0,0);
CGPathAddLineToPoint(path, NULL, v.bounds.size.width,0);
CGPathAddLineToPoint(path, NULL, v.bounds.size.width,v.bounds.size.height);
CGPathAddLineToPoint(path, NULL, 0,v.bounds.size.height);
CGPathCloseSubpath(path);
//绘制渐变
UIColor *starColor=[UIColor colorWithRed:127.0/255 green:175.0/255 blue:174.0/255 alpha:1.0];
UIColor *endColor=[UIColor colorWithRed:204.0/255 green:233.0/255 blue:233.0/255 alpha:1.0];
[self drawLinearGradient:gc path:path startColor:starColor.CGColor endColor:endColor.CGColor View:v];
//注意释放CGMutablePathRef
CGPathRelease(path);
//从Context中获取图像，并显示在界面上
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return img;
}
2-> 圆半径方向渐变
- (void)drawRadialGradient:(CGContextRef)context
path:(CGPathRef)path
startColor:(CGColorRef)startColor
endColor:(CGColorRef)endColor
{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat locations[] = { 0.0, 1.0 };
NSArray *colors = @[(__bridgeid) startColor, (__bridgeid) endColor];
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);
CGRect pathRect = CGPathGetBoundingBox(path);
CGPoint center = CGPointMake(CGRectGetMidX(pathRect), CGRectGetMidY(pathRect));
CGFloat radius = MAX(pathRect.size.width / 2.0, pathRect.size.height / 2.0) * sqrt(2);
CGContextSaveGState(context);
CGContextAddPath(context, path);
CGContextEOClip(context);
CGContextDrawRadialGradient(context, gradient, center, 0, center, radius, 0);
CGContextRestoreGState(context);
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
//创建CGContextRef
UIGraphicsBeginImageContext(self.view.bounds.size);
CGContextRef gc = UIGraphicsGetCurrentContext();
//创建CGMutablePathRef
CGMutablePathRef path = CGPathCreateMutable();
//绘制Path
CGRect rect = CGRectMake(0, 100, 300, 200);
CGPathMoveToPoint(path, NULL, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMidX(rect), CGRectGetMaxY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetWidth(rect), CGRectGetMaxY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetWidth(rect), CGRectGetMinY(rect));
CGPathCloseSubpath(path);
//绘制渐变
[self drawRadialGradient:gc path:path startColor:[UIColor greenColor].CGColor endColor:[UIColor redColor].CGColor];
//注意释放CGMutablePathRef
CGPathRelease(path);
//从Context中获取图像，并显示在界面上
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView *imgView = [[UIImageView alloc] initWithImage:img];
[self.view addSubview:imgView];
}
3. 以CAShapeLayer作为layer的mask属性
CALayer的mask属性可以作为遮罩让layer显示mask遮住(非透明)的部分；CAShapeLayer为CALayer的子类，通过path属性可以生成不同的形状，将CAShapeLayer对象用作layer的mask属性的话，就可以生成不同形状的图层。故生成颜色渐变有以下几个步骤：
生成一个imageView(也可以为layer)，image的属性为颜色渐变的图片
生成一个CAShapeLayer对象，根据path属性指定所需的形状
将CAShapeLayer对象赋值给imageView的mask属性
- (void)viewDidLoad
{
[super viewDidLoad];
[self.view addSubview:self.firstCircle];
_firstCircle.frame = CGRectMake(0, 0, 200, 200);
_firstCircle.center = CGPointMake(CGRectGetWidth(self.view.bounds) / 2.0, CGRectGetHeight(self.view.bounds) / 2.0);
CGFloat firsCircleWidth = 5;
self.firstCircleShapeLayer = [self generateShapeLayerWithLineWidth:firsCircleWidth];
_firstCircleShapeLayer.path = [self generateBezierPathWithCenter:CGPointMake(100, 100) radius:100].CGPath;
_firstCircle.layer.mask = _firstCircleShapeLayer;
}
- (CAShapeLayer *)generateShapeLayerWithLineWidth:(CGFloat)lineWidth
{
CAShapeLayer *waveline = [CAShapeLayer layer];
waveline.lineCap = kCALineCapButt;
waveline.lineJoin = kCALineJoinRound;
waveline.strokeColor = [UIColor redColor].CGColor;
waveline.fillColor = [[UIColor clearColor] CGColor];
waveline.lineWidth = lineWidth;
waveline.backgroundColor = [UIColor clearColor].CGColor;
return waveline;
}
- (UIBezierPath *)generateBezierPathWithCenter:(CGPoint)center radius:(CGFloat)radius
{
UIBezierPath *circlePath = [UIBezierPath bezierPathWithArcCenter:center radius:radius startAngle:0 endAngle:2*M_PI clockwise:NO];
return circlePath;
}
- (UIImageView *)firstCircle
{
if (!_firstCircle) {
self.firstCircle = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"circleBackground"]];
_firstCircle.layer.masksToBounds = YES;
_firstCircle.alpha = 1.0;
}
return _firstCircle;
}
=========CGPATH===
//创建CGContextRef UIGraphicsBeginImageContext(self.view.bounds.size); CGContextRef gc = UIGraphicsGetCurrentContext(); //=== 绘画逻辑 === //创建用于转移坐标的Transform，这样我们不用按照实际显示做坐标计算 CGAffineTransform transform = CGAffineTransformMakeTranslation(50, 50); //创建CGMutablePathRef CGMutablePathRef path = CGPathCreateMutable(); CGPathAddArc(path, &transform, 50, 50, 50, 0, 1.5 * M_PI, NO); CGPathMoveToPoint(path, &transform, 50, 0); CGPathAddLineToPoint(path, &transform, 50, 50); CGPathAddLineToPoint(path, &transform, 100, 50); //将CGMutablePathRef添加到当前Context内 CGContextAddPath(gc, path); [[UIColor grayColor] setFill]; [[UIColor blueColor] setStroke]; CGContextSetLineWidth(gc, 2); //执行绘画 CGContextDrawPath(gc, kCGPathFillStroke); //从Context中获取图像，并显示在界面上 UIImage *img = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); UIImageView *imgView = [[UIImageView alloc] initWithImage:img]; [self.view addSubview:imgView];
======文字渐变
方法一：设置一张带有渐变的图片，
UIColor *color=[UIColorcolorWithPatternImage:[UIImageimageNamed:@"带渐变色的图片"]];
方法二：
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