iOSCoreGraphics基础入门（3）

## 绘制阴影// 创建一块画布
CGContextRef context &＃61; UIGraphicsGetCurrentContext();// 添加阴影颜色
CGContextSetShadowWithColor(context, CGSizeMake(1.2, 1.2), 0, [UIColor lightGrayColor].CGColor);// 绘制字符串
[&＃64;"Hello" drawAtPoint:CGPointMake(20, 100)withAttributes:&＃64;{ NSFontAttributeName: [UIFont systemFontOfSize:20]}];


## 绘制图片UIImage* image &＃61; [UIImage imageNamed:&＃64;"02"];// 第一种方法
[image drawAtPoint:CGPointMake(0, 0)];// 第二种方法
[image drawInRect:CGRectMake(20.f, 20.0f, 320 / 2.f, 568 / 2.f)];


## 绘制屋顶- (void)drawRect:(CGRect)rect
{[self drawRooftopAtTopPointof:CGPointMake(160.0f, 40.0f) textToDisplay:&＃64;"Miter" lineJoin:kCGLineJoinMiter];[self drawRooftopAtTopPointof:CGPointMake(160.0f, 180.0f) textToDisplay:&＃64;"Bevel" lineJoin:kCGLineJoinBevel];[self drawRooftopAtTopPointof:CGPointMake(160.0f, 320.0f) textToDisplay:&＃64;"Round" lineJoin:kCGLineJoinRound];
}- (void)drawRooftopAtTopPointof:(CGPoint)paramTopPoint textToDisplay:(NSString * )paramText lineJoin:(CGLineJoin)paramLineJoin
{[[UIColor brownColor] set];CGContextRef currentContext &＃61; UIGraphicsGetCurrentContext();CGContextSetLineJoin(currentContext,paramLineJoin);CGContextSetLineWidth(currentContext, 20.0f);CGContextMoveToPoint(currentContext, paramTopPoint.x - 140, paramTopPoint.y &＃43; 100);CGContextAddLineToPoint(currentContext, paramTopPoint.x, paramTopPoint.y);CGContextAddLineToPoint(currentContext, paramTopPoint.x &＃43; 140, paramTopPoint.y &＃43; 100);CGContextStrokePath(currentContext);[[UIColor blackColor] set];[paramText drawAtPoint:CGPointMake(paramTopPoint.x - 40.0f, paramTopPoint.y &＃43; 60.0f) withFont:[UIFont boldSystemFontOfSize:30.0f]];
}

## 绘制矩形CGContextRef context &＃61; UIGraphicsGetCurrentContext();
CGMutablePathRef path &＃61; CGPathCreateMutable();CGPathAddRect(path, NULL, CGRectMake(0, 0, 200, 300));
CGContextAddPath(context, path);[[UIColor colorWithRed:1 green:0 blue:0 alpha:1] setFill];
[[UIColor greenColor] setStroke];
CGContextSetLineWidth(context, 5.0f);CGContextDrawPath(context, kCGPathFillStroke);
CGPathRelease(path);


## 绘制多个矩形CGContextRef context &＃61; UIGraphicsGetCurrentContext();
CGMutablePathRef path &＃61; CGPathCreateMutable();CGRect rectangle1 &＃61; CGRectMake(20.0f, 20.0f, 200.0f, 300.0f);
CGRect rectangle2 &＃61; CGRectMake(40.0f, 100.0f, 90.0f, 300.0f);
CGRect rectangles[2] &＃61; {rectangle1, rectangle2};CGPathAddRects(path, NULL, (const CGRect *)&rectangles, 2);CGContextAddPath(context, path);[[UIColor colorWithRed:0 green:1 blue:0 alpha:1] setFill];
[[UIColor blackColor] setStroke];CGContextDrawPath(context, kCGPathFillStroke);
CGPathRelease(path);

## 绘制渐变效果CGColorSpaceRef colorSpace &＃61; CGColorSpaceCreateDeviceRGB();
UIColor * startColor &＃61; [UIColor blueColor];
CGFloat * startColorComponents &＃61; (CGFloat *)CGColorGetComponents([startColor CGColor]);
UIColor * endColor &＃61; [UIColor greenColor];
CGFloat * endColorComponents &＃61; (CGFloat *)CGColorGetComponents([endColor CGColor]);CGFloat colorComponents[8] &＃61; {startColorComponents[0],startColorComponents[1],startColorComponents[2],startColorComponents[3],endColorComponents[0],endColorComponents[1],endColorComponents[2],endColorComponents[3]
};CGFloat colorIndices[2] &＃61; {0.0f,1.0f};
CGGradientRef gradient &＃61; CGGradientCreateWithColorComponents(colorSpace, (const CGFloat *)&colorComponents, (const CGFloat *)&colorIndices, 2);
CGColorSpaceRelease(colorSpace);CGRect screenBounds &＃61; [[UIScreen mainScreen] bounds];
CGPoint startPoint, endPoint;
startPoint &＃61; CGPointMake(0.0f, screenBounds.size.height/2.0f);
endPoint &＃61; CGPointMake(screenBounds.size.width, startPoint.y);CGContextRef currentContext &＃61; UIGraphicsGetCurrentContext();
CGContextDrawLinearGradient(currentContext,gradient , startPoint, endPoint, 0);CGGradientRelease(gradient);