iOS-OC-DrawRect使用小谈

1.将一张图片通过画图画到背景视图上,如果背景图片比图片大图片会铺开;

UIImage *bgimage = [UIImage imageNamed:@"ec.jpg"];
    [bgimage drawAsPatternInRect:self.bounds];//将图像作为一个CGPattern

2. 将一张图片通过画图画到背景视图上 ,图片会铺满整个view

UIImage *bgimage = [UIImage imageNamed:@"ec.jpg"];
    //[bgimage drawAsPatternInRect:self.bounds];//将图像作为一个CGPattern
    [bgimage drawAtPoint:CGPointMake(0, 0)];
    [bgimage drawInRect:self.bounds];

3. 通过混合模式绘制，得到不同效果的图片

UIImage *image = [UIImage imageNamed:@"w.jpg"];
    [image drawAtPoint:CGPointMake(50, 50)];
    [image drawAtPoint:CGPointMake(30, 50) blendMode:kCGBlendModeExclusion alpha:1];

4. 改变字体大小和颜色

NSString *str = @"月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚，月黑风高的夜晚";
    [str drawInRect:self.bounds withAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:15],NSForegroundColorAttributeName:[UIColor blueColor]}];

5.画出几跳线，绘制想要的形状（三角形）

CGContextRef ref = UIGraphicsGetCurrentContext();
    //移动到某一点
    CGContextMoveToPoint(ref, 50, 50);
    //添加一条直线
    CGContextAddLineToPoint(ref, 250, 50);
    CGContextAddLineToPoint(ref, 150, 150);
    CGContextAddLineToPoint(ref, 50, 50);
    CGContextClosePath(ref);

6.设置线条的颜色，设置虚线等等；

CGContextRef ref = UIGraphicsGetCurrentContext();
    //移动到某一点
    CGContextMoveToPoint(ref, 50, 50);
    //添加一条直线
    CGContextAddLineToPoint(ref, 250, 50);
    CGContextAddLineToPoint(ref, 150, 150);
    CGContextAddLineToPoint(ref, 50, 50);
    CGContextClosePath(ref);
    
    //设置线条的颜色
    CGContextSetStrokeColorWithColor(ref, [UIColor redColor].CGColor);
    CGContextSetLineWidth(ref, 10.0);
    //设置相交点
    CGContextSetLineJoin(ref, kCGLineJoinBevel);
    //设置虚线
    CGFloat leghths[] = {20,10};
    //第二个参数  是开始画的位置
    CGContextSetLineDash(ref, 0, leghths, 2);
    CGContextSetLineCap(ref, kCGLineCapRound);
    //开始画
    CGContextStrokePath(ref);

7.绘制一个矩形，并且填充颜色；

//设置填充颜色
    CGContextSetFillColorWithColor(ref, [UIColor lightGrayColor].CGColor);
    //添加一个矩形
    CGContextAddRect(ref, CGRectMake(50, 220, 150, 150));
    CGContextSetShadow(ref, CGSizeMake(20, 20), 10);
    CGContextSetShadowWithColor(ref, CGSizeMake(20, 20), 20, [UIColor purpleColor].CGColor);
    CGContextFillPath(ref);
    CGContextDrawPath(ref, kCGPathFillStroke);

8.绘制圆形，扇形；

CGContextRef ref1 = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(ref1, [UIColor orangeColor].CGColor);
    CGContextMoveToPoint(ref1, 150, 150);
    //弧线
    CGContextAddArc(ref1, 150, 150, 100, 0, 80*M_PI/180, 1);
    CGContextFillPath(ref1);

9. 绘制圆形缺省部分的颜色

//绘制圆形缺省部分的颜色
    CGContextSetFillColorWithColor(ref1, [UIColor cyanColor].CGColor);
    CGContextMoveToPoint(ref1, 155, 155);
    CGContextAddArc(ref1, 155, 155, 100, 0, 80*M_PI/180, 0);
    CGContextFillPath(ref1);

10. 绘制曲线图（抛物线）

CGContextMoveToPoint(ref1, 50, 300);
    CGContextAddQuadCurveToPoint(ref1, 150, 500, 250, 300);
    CGContextStrokePath(ref1);